Airway Management

VII

Chapter

119

Airway Management Ann E. Thompson and Rosanne Salonia

PEARLS • S afe management of the critically ill child’s airway requires an understanding of the anatomic and physiologic changes that occur from birth through adolescence, recognition of congenital and acquired airway abnormalities, appreciation of the pathophysiologic consequences of airway manipulation, and preparation for airways that are potentially difficult to manage. • L aryngoscopy and intubation are potent physiologic stimuli that are associated with severe discomfort, profound cardiovascular and cerebrovascular changes, and increased airway reactivity. • R  ecognizing and preparing to manage a difficult airway are essential for the prevention of potentially lethal complications of intubation. • T he approach to intubation must be tailored to specific circumstances, such as a full stomach, elevated intracranial pressure, cervical spine injury, and upper airway obstruction. • A  lternative approaches to airway management, such as the lighted stylet, laryngeal mask airway, cricothyrotomy, retrograde intubation, and tracheostomy, may be lifesaving.

Accurate assessment and safe management of the airway of a critically ill child is the essential first step in providing effective intensive care. It requires understanding of the anatomic and physiologic changes that occur from birth through adolescence, recognition of congenital and acquired airway abnormalities, appreciation of the pathophysiologic consequences of airway manipulation, and preparation for airways that may potentially be difficult to manage.

Anatomic Considerations The configuration of the child’s airway changes dramatically from birth to adulthood (Figure 119-1). The nose is the site of nearly half of the total respiratory resistance to air flow at all ages. The infant’s nose is short, soft, and flat, with small, nearly circular nares. The nasal valve, the narrowest portion of the nasal airway, approximately 1 cm proximal to the alar rim in newborns, measures only about 20 mm2.1,2 By 6 months, dimensions of the nares have nearly doubled, but they are still 1590

easily occluded by edema, secretions, or external pressure. Although an infant is perhaps not as much the obligate nose breather as commonly assumed, signs of airway obstruction frequently develop when the infant’s nose is blocked.3,4 In infancy the mandible is small and the basicranium (which provides the roof of the nasopharynx) is flat, creating a small oral cavity. Over the years of its development, the jaw grows primarily down and forward, with the ramus increasing in height and width. The posterior portion of the basicranium develops a progressively more rounded configuration through childhood, which results in a larger nasal airway to meet the need for increased air flow (and provides a chamber for the resonance of adult speech). Under normal conditions, the genioglossus muscle and other muscles of the pharynx and larynx help maintain airway patency. Both tonic and phasic inspiratory activity synchronized with phrenic contraction have been noted in animal and human studies. In particular, the genioglossus increases the dimensions of the pharyngeal airway by displacing the tongue anteriorly.5 In the infant and young child, the tongue is large relative to the bony structures surrounding it and the cavities they form. Relatively little displacement is possible at any time, and loss of tone during sleep, sedation, or central or peripheral nervous system dysfunction is more likely than in older patients to allow the tongue to relax into the posterior pharynx and cause upper airway obstruction. The infant larynx is high in the neck at birth, with the epiglottis at the level of the first cervical vertebra and overlapping the soft palate. This approximation of structures, in combination with the relatively large tongue and small mandible, probably contributes to the vulnerability to airway obstruction in infants and young children. By 6 months the epiglottis has moved to about the level of the third cervical vertebra and is separate from the palate. It continues to descend to its adult position at about the fifth or sixth cervical vertebra by early adolescence. The infant epiglottis is soft and omega shaped, in contrast with the more rigid, flatter adult structure, and it has greater potential to occlude the airway. The immature larynx is funnel shaped, with the subglottic portion angled posteriorly relative to the supraglottic portion rather than forming a straight vertical column, as seen in adults. The larynx tapers to the cricoid cartilage, the narrowest point in the child’s extrathoracic airway. The internal dimensions of the trachea in a newborn are approximately one third those of an adult, and absolute

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P 1 2 3

E P

Newborn E

A

18 months

B Infant

Adult Inflammation 0.5

Child Cricoid

C

r R (normal) R (inflamed)

1 1 16

3 0.01 0.03

Narrowest point

D

Adult Figure 119–1.  Characteristics of the pediatric airway. A, Changes in mandibular shape from infancy through adolescence. B, The epiglottis is initially cephalad in infancy, then descends throughout childhood. E, Epiglottis; P, palate. C, Edema has a much greater effect on airways resistance in the young child than later in life. r, Relative radius of the trachea; R, relative airways resistance. D, The cricoid is the narrowest portion of the airway until age 8 to 10 years.

resistance to air flow is higher in newborns than in older children and adults. Because the most important factor determining resistance (R) is the radius (r) of an airway (R proportional to 8 l/r4), small changes in airway diameter in infants or young children as a consequence of edema or secretions have a far greater effect on resistance than similar changes in larger patients (see Figure 119-1).

Basic Airway Management Airway management depends on a brisk assessment of the patient’s breathing and knowledge of the likely progression of the airway problem, that is, deterioration versus improving function. In virtually any setting in which respiratory difficulty is suspected, oxygen should be administered until the specific abnormality can be identified and adequately treated. Although extreme hypercarbia usually is well tolerated, hypoxia is routinely catastrophic and is not necessarily obvious on initial examination. From the alveolar air equation, it is obvious that hypercarbia produces hypoxia at low fraction of inspired oxygen (Fio2) (Table 119-1). If the patient is breathing spontaneously, attention is directed first to signs of upper airway obstruction, including absence of audible or palpable air flow, stertorous sounds, stridor, or a rocking chest and abdominal motion rather than the normal, smooth rise and fall that should occur with inspiration and expiration. An alert child with normal neuromuscular function usually instinctively assumes a body position that minimizes upper airway obstruction. However, a child with an altered level of consciousness or severe neuromuscular weakness may be unable to maintain a patent airway because of the inability to alter his or her position or maintain adequate glossopharyngeal muscle tone.

Table 119–1  Impact of Providing ­Supplemental Oxygen During Hypercarbia on Alveolar Oxygen Tension Alveolar gas equation:

Pao2 = Fio2 (PB – Ph2o) – Paco2/0.8

Room air, normocarbia:

Pao2 = 0.21 (760 – 47) – 40/0.8 = 99 mm H2O

Room air, hypercarbia:

Pao2 = 0.21 (760 – 47) – 80/0.8 = 50 mm H2O

Supplemental O2, hypercarbia:

PAo2 = 0.4 (760 – 47) – 80/0.8 = 185 mm H2O

Fio2, Fraction of inspired oxygen; Pao2, partial pressure of oxygen, alveolar.

Nasopharyngeal Airway A nasopharyngeal airway that extends through nasal passages to the posterior pharynx and beyond the base of the tongue often is adequate to relieve obstruction and is tolerated by most patients, even those who are conscious (Figure 119-2). An appropriate-size airway extends from the nares to the tragus of the ear and is of the largest diameter that passes through nasal passages without causing blanching of the skin surrounding the nares. The airway tube should be well lubricated before placement. Risks of nasopharyngeal airways include nasal ulceration, bleeding, laceration of friable lymphoid tissue, rupture of a pharyngeal abscess, laryngospasm, and potential passage through the cribriform plate in patients with basilar skull fractures. Topical vasoconstricting agents reduce but do not eliminate the risk of bleeding. Like other nasal tubes, use of nasal airways increases the risk of sinusitis;

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among the flow rate, patient size, and anatomy of the patient’s airway, but it is probably limited to 4 to 5 cm H2O.6,7 At least in infants, positive pressure generation requires a closed mouth.8

Oxygen Hoods

Figure 119–2.  Nasopharyngeal and oropharyngeal airways in good ­position.

therefore, contraindications to their use include severe coagulopathy, cerebrospinal fluid (CSF) leaks, and basilar skull fractures.

Oropharyngeal Airways Oropharyngeal airways displace the base of the tongue from the posterior pharyngeal wall and break contact between the tongue and palate (see Figure 119-2). Size selection is important. An excessively long airway may encroach upon the larynx and cause laryngospasm. An airway that is too short may actually push the tongue posteriorly and exacerbate obstruction. If the airway is held at the side of the face with the flange just anterior to the incisors, the tip should be at or near the angle of the mandible. The airway should be positioned following the curve of the tongue while the tongue is held down and forward with a tongue depressor. Inserting the airway with its concave side facing the palate and then rotating it may traumatize the oral mucosa or damage teeth. Oral airways are poorly tolerated in any patient with a functional gag reflex and may induce vomiting. As a consequence, they are of little more than temporary value in the critically ill child. They may support a patent airway for bag-valve-mask ventilation in preparation for intubation.

Oxygen Delivery Devices Nasal Cannulas Nasal cannulas consist of two hollow prongs projecting from a hollow face piece. Humidified oxygen (100%) flows from a standard source, effectively delivering a pharyngeal concentration of 25% to 40% after mixing with variable amounts of room air. The cannulas are easy to use, often readily tolerated, lightweight, economical, and disposable and take advantage of the humidifying properties of the nasopharynx. Flow typically is limited to only 3 to 5 L/min because of the extent to which relatively dry gas flow cools and dries the nasal airway. The use of nasal cannulas is limited by the relatively low oxygen concentration that can be delivered. High-flow nasal cannulas can deliver up to 40 L/min of warmed, humidified gas and are generally very well tolerated, although the noise level for the patient can be high. The oxygen concentration delivered is higher than with simple nasal cannulas. High-flow nasal cannulas generate positive distending pressure similar to that provided by nasal continuous positive airway pressure. The pressure generated is dependent on the interaction

Oxygen hoods are cylinders or boxes that enclose an infant’s or small child’s head. Oxygen enters through a gas inlet port, and exhaled gas leaves primarily through the opening for the neck. Hoods provide up to 80% to 90% oxygen, good humidification, and controlled temperature. They allow easy access to the child for other care. Tents for older children provide the same environment advantages but allow less ready access to the patient and usually provide only 21% to 50% oxygen. Both have the disadvantage of being very noisy for the patient and are much less commonly used than in the past.

Masks A variety of masks are available for delivering oxygen. Simple masks fit loosely. The oxygen concentration delivered varies, depending on the patient’s inspiratory flow rate and the oxygen flow into the system. Partial rebreathing masks incorporate some sort of reservoir, usually a bag below the chin. Provided that flow into the system exceeds the patient’s minute ventilation and that the bag does not collapse on inspiration, little carbon dioxide is inhaled, and concentrations of oxygen up to about 60% can be achieved. Nonrebreathing masks must fit snugly. They incorporate a mask, reservoir, and one-way valves that vent expired gas but do not permit inspiration of room air. As a result, they can deliver close to 100% oxygen. Noninvasive Positive Pressure Ventilation. Continuous positive airway pressure (CPAP) delivers high concentrations of oxygen and maintains positive airway pressure in the spontaneously breathing patient. CPAP is applied with an oxygen source connected to either a tight-fitting nasal or full-face mask or helmet in children or via nasal prongs in the neonate and older infant. CPAP offers the benefit of maintaining alveolar expansion and decreases work of breathing for many patients, particularly those with pulmonary parenchymal disease, as well as for some patients with airway obstruction related to poor upper airway tone or laryngeal, tracheal, or bronchomalacia. Like CPAP, bilevel positive airway pressure (BiPAP) can be provided by mask, but it requires a ventilator to assist with flow delivery. The patient’s inspiratory effort triggers the BiPAP machine to deliver decelerating flow in order to reach a preset pressure, defined as inspiratory positive airway pressure. When a patient’s own inspiratory flow falls below a preset amount, ventilatory assistance ceases and maintains expiratory airway pressure at a predetermined value (typically between 5 and 10 mm Hg). Uses in the pediatric intensive care unit (PICU) include upper airway obstruction, atelectasis, exacerbations of neuromuscular disorders, support for mild to moderate respiratory failure, and as an assist in weaning patients from invasive mechanical ventilation. Both CPAP and BiPAP offer the advantage of providing respiratory support without endotracheal intubation but require that the child tolerate a close-fitting mask. A more extensive discussion of CPAP and BiPAP is available in Chapter 49, Mechanical Ventilation and Respiratory Care.

Chapter 119 — Airway Management

Establishing a Functional Airway A patient who is apneic or in very severe respiratory distress requires ventilation assisted initially with a bag and mask. Probably no skill is more important for the intensivist than the ability to provide effective manual bag-mask ventilation. It can be lifesaving while preparation for endotracheal intubation proceeds or when intubation cannot be accomplished. Effective technique requires positioning the patient adequately to open the upper airway, achieving a good mask-face seal, inserting an oral or nasal airway if needed, and generating an adequate tidal volume, coordinating manual breaths with patient efforts when they are present. Poor technique results in ineffective oxygenation and ventilation, gastric insufflation, and increased risk of aspiration. If the child is too weak or obtunded to maintain pharyngeal tone independently, the head should be placed on a thin cushion to cause slight cervical spine flexion and gentle extension at the atlantooccipital joint. In infants, the large occipitofrontal diameter makes the cushion unnecessary, although a thin pad under the shoulders may be useful. It appears that aligning the external auditory meatus with the sternal notch is a reasonable guide to appropriate positioning. Current recommendations are to avoid overextending the baby’s very flexible cervical spine, which may stretch and compress the trachea and potentiate, rather than relieve, obstruction. Studies have questioned the existence of this phenomenon but to date have included a very small number of infants, all with normal airways.9 Appropriate head tilt separates the tongue from the posterior pharyngeal wall. If airway obstruction persists, the chin can be pulled forward by encircling the mandible behind the lower incisors between the thumb and fingers. The most effective means of relieving functional obstruction is the so-called triple

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airway maneuver: With the fingers behind the vertical ramus of the jaw, the mandible is displaced downward, forward, and finally upward again until the mandible and lower incisors are anterior to the maxilla. This action effectively pulls the tongue forward and away from the pharyngeal wall. In some patients, establishing a functional airway is sufficient to allow resumption of effective spontaneous ventilation. In other patients, steady positive airway pressure is necessary to overcome residual obstruction. If breathing remains inadequate, manual ventilation is necessary. Effective ventilation requires a good mask fit. The mask should sit smoothly on the bridge of the nose and the bony prominence of the chin. It is important to avoid airway occlusion with the mask or hand or pressure on eyes, soft nasal structures, or branches of the trigeminal and facial nerves. A good mask fit is predictably difficult in a patient without teeth, a very flat or prominent nose, or micrognathia. Insertion of a nasal or oropharyngeal airway may help maintain an adequate airway. Once a good mask fit is ensured, ventilation may be assisted. Two types of bags are in general use: self-inflating resuscitation bags and standard anesthesia bags. Because self-inflating bags vary substantially, specific directions for their use must be followed carefully. All bags incorporate an adapter to connect to a mask or endotracheal tube, a bag, a pressure-relief valve, and a port for fresh gas inflow. Most bags designed for children have pressure-relief valves designed to pop off at 35 to 45 cm H2O pressure to prevent excessive volume delivery and subsequent barotrauma. In patients with very poor compliance or increased airway resistance, it may be necessary to bypass this valve temporarily to provide effective ventilation. Most systems incorporate valves that prevent rebreathing. Fresh gas flows through the valve on spontaneous inspiration (negative pressure) or on creation of positive pressure by squeezing the bag (Figure 119-3). Exhaled gas is vented to

Angular patient valve

Exhalation ports From patient

Pressure relief valve EXHALATION Bag inlet valve Safety outlet valve (oxygen) Reservoir bag

To patient

INHALATION

One-way leaf valve Oxygen inlet Safety inlet valve (air)

Figure 119–3.  Self-inflating manual ventilation bag with tubing as a reservoir. Inset shows function of one type of valve, permitting manual positive pressure breathing, or spontaneous breathing, but requiring generation of negative pressure by the patient to open the valve. Simply holding the mask over the patient’s face does not provide supplemental oxygen.

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the atmosphere. Not all systems allow spontaneous breathing; those that do demand that the patient generate at least a little negative pressure, so a good mask fit is necessary. Holding the mask above the patient’s face provides no supplemental oxygen. The percentage of oxygen delivered depends on the percentage of oxygen from the source, the fresh gas flow rate, and the respiratory rate, which determines the time available for the bag to refill. Most systems require some sort of reservoir assembly in addition to the self-inflating bag to prevent entrainment of room air. With a reservoir, 100% oxygen may be delivered; without a reservoir, most deliver less than 50%. Anesthesia bags require flow from a source of gas under pressure in order to expand. Many variations have been reviewed extensively in the anesthesia literature. These circuits depend on the location of the fresh gas inflow and overflow valves, the rate of fresh gas flow, the respiratory rate, tidal volume, carbon dioxide production, and whether ventilation is spontaneous or controlled. Many ICUs use the Mapleson D configuration, with the fresh gas source attached just distal to the patient connection. The overflow valve is proximal to the reservoir bag. During expiration, the patient’s exhaled tidal volume mixes with fresh gas flowing into the system and accumulates in the tubing and bag. With sufficiently high fresh gas flow, alveolar gas is washed to the overflow valve and eliminated from the circuit. The system requires higher fresh gas flow to avoid rebreathing during spontaneous ventilation than during controlled breathing, but a safe rule of thumb recommends fresh gas flow two to three times the minute ventilation. During controlled ventilation, a minimum of 100 mL/kg/ min ensures that carbon dioxide elimination is proportional to minute ventilation.10,11 At flows less than 90 mL/kg/min, increasing ventilation may only increase CO2 rebreathing.

Endotracheal Intubation The pediatric intensivist is frequently called upon to intubate critically ill patients when brief periods of ventilation with a bag and mask are inadequate to reverse the underlying disorder. Few of these intubations are performed under the optimal conditions commonly attainable in the operating room, that is, relatively healthy children with empty stomachs who have previously been sedated and are intubated in a controlled environment with all members of the team experienced in and prepared for airway management. Instead, patients are often critically unstable and require intubation suddenly, often in settings where the procedure is not routine. Intubation often is viewed only as a means to an end, namely, mechanical ventilation. However, it is associated with profound physiologic effects that may dramatically affect the patient. The intensivist’s appreciation of these factors and ability to minimize the adverse physiologic consequence of airway manipulation may as decisively determine patient outcome as his or her skill in providing the intensive care that follows.

Indications Respiratory Failure Respiratory failure may result from dysfunction at any point along the ventilatory pathway. To provide appropriate support and to avoid hazards specific to the individual disorder, airway intervention must be tailored to the underlying cause.

Outside the operating room, the need for intubation is most commonly associated with respiratory failure resulting from upper or lower airway or pulmonary parenchymal disorders that require mechanical ventilation. Respiratory failure is defined in terms of excessive work of breathing or inadequate oxygenation (in the absence of cyanotic congenital heart disease) or carbon dioxide elimination. Box 119-1 contains one set of criteria for intubation.

Hemodynamic Instability Patients with hemodynamic instability often benefit from assisted ventilation. The need for controlled ventilation as a component of cardiopulmonary resuscitation is obvious. In addition, early intubation in anticipation of impending cardiovascular collapse may prevent catastrophic tissue hypoxia. Redistribution of blood flow away from respiratory muscles, especially the diaphragm, in patients with marginal cardiac output may improve perfusion of other vital organs, including the heart, and help prevent cardiac arrest.12-16

Neuromuscular Dysfunction For additional information on neuromuscular dysfunction, see Chapter 58. Neuromuscular dysfunction or severe chest wall instability (or deformity) may cause failure of the bellows apparatus for breathing.17 Initially, tidal volume remains normal or at least sufficient to maintain normal blood gas tensions, but vital capacity and maximal inspiratory and expiratory pressures decrease. Inability to take a deep breath or cough forcefully risks progressive segmental or lobar atelectasis, inability to clear secretions, bronchial obstruction, and possible major airway obstruction with sudden severe hypoxia or carbon dioxide retention. Increasing weakness results in progressively smaller tidal volumes, loss of upper airway tone, and, ultimately, inadequate minute ventilation. Bulbar dysfunction may lead to aspiration as a result of impaired swallowing and inadequate cough. Measurement of ventilatory reserve provides a better assessment of the patient’s need for ventilatory assistance than does arterial blood gas tensions alone. Maximum negative inspiratory pressure and vital capacity are two simple, commonly Box 119–1  Indications for Intubation 1. Pao2 <60 mm Hg with fraction of inspired oxygen ≥0.6 (in absence of cyanotic congenital heart disease) 2. Paco2 >50 mm Hg (acute and unresponsive to other intervention) 3. Upper airway obstruction, actual or impending 4. Neuromuscular weakness • Maximum negative inspiratory pressure ≥20 cm H2O • Vital capacity <12–15 mL/kg 5. Absent protective airway reflexes (cough, gag) 6. Hemodynamic instability (cardiopulmonary resuscitation, shock) 7. Controlled therapeutic (hyper)ventilation • Intracranial hypertension • Pulmonary hypertension • Metabolic acidosis 8. Pulmonary toilet 9. Emergency drug administration

Chapter 119 — Airway Management

used tests for this purpose. A variety of other measures also help assess respiratory “strength,” but most are difficult to perform in sick, uncooperative infants and children. Patients with diffuse neuromuscular weakness of any cause, spinal cord dysfunction above the level of T6, or loss of phrenic nerve or diaphragm function are particularly prone to respiratory failure.18 Because of the extreme compliance of their chest walls and relative ineffectiveness of intercostal muscles, infants younger than approximately 6 months tolerate diaphragmatic paralysis poorly.19-23 Many patients with neuromuscular weakness respond well to noninvasive forms of ventilatory support.17,24 Decisions about the best approach to airway management should be based on the nature and likely progression of the illness, the child’s maturity and level of consciousness, and the timing of the onset of respiratory insufficiency. In an emergency, endotracheal intubation is likely to be safest, with transition to noninvasive support when careful planning allows.24

Failure of Central Nervous System Regulation of Ventilatory Drive Failure of central nervous system regulation of ventilatory drive may prompt intubation (see Chapters 54 and 57). Centrally mediated hypoventilation is manifest as CO2 retention, usually in the absence of increased work of breathing. On occasion the decision to support ventilation may be based on observing abnormal ventilatory patterns in anticipation of neurologic deterioration. Loss of protective airway reflexes, including the cough and gag reflexes, can result from central nervous system depression, cranial nerve abnormalities, or severe motor weakness. In such patients, intubation is indicated to prevent aspiration. Intubation may be appropriate in anticipation of the need to protect the airway and support ventilation during deep sedation for procedures or diagnostic studies.

Other Indications Intubation is indicated as a step toward therapeutic controlled (hyper)ventilation (e.g., in patients with increased intracranial pressure [ICP] or pulmonary hypertension) or to support spontaneous hyperpnea in patients with metabolic acidosis and other conditions. Patients with profuse, thick, or tenacious secretions (e.g., as a result of bacterial pneumonitis or smoke inhalation) may benefit from an artificial airway as a means of providing effective suction. Impaired mucociliary clearance occurs in patients exposed to high oxygen concentrations or other airway irritants (including particulate and gaseous components of smoke), those experiencing severe hypoxia or hypercarbia, and, paradoxically, those who have airway trauma induced by endotracheal intubation and suctioning. Endotracheal intubation also provides an effective means of delivering drugs during cardiopulmonary resuscitation when venous or intraosseous access is not available (see Chapter 34).

Physiologic Effects of Intubation Laryngoscopy is a potent physiologic stimulus (Box 119-2).25,26 At the very least, laryngoscopy is uncomfortable, causing significant pain and severe anxiety, especially in children who cannot understand or accept the need for it. Laryngoscopy causes an increase in systemic blood pressure

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Box 119–2  Potential Physiologic Effects of Laryngoscopy and Intubation Pain Tachycardia Anxiety Bradycardia Hypoxia Systemic hypertension Hypercarbia Decreased systemic venous return Increased intraocular Decreased jugular venous pressure return Increased intragastric pressure Increased intracranial pressure Laryngospasm Bronchoconstriction Pulmonary hypertension

and heart rate initiated by pressure on the back of the tongue or lifting the epiglottis.27 This effect is augmented by endotracheal intubation and suction.28 Nodal or ventricular dysrhythmias may occur. Sensory impulses triggering this reflex probably are carried along the vagus nerve supplying the base of the tongue, epiglottis, and trachea. The efferent limb is less well defined but most likely is the product of enhanced sympathetic activity. Infants respond more variably than do older patients. Hypertension develops in most patients, but a few become hypotensive, especially if they are hypoxic.29 They may demonstrate moderate-to-severe bradycardia rather than tachycardia, perhaps as a consequence of their greater parasympathetic tone. Sedation and light anesthesia decrease but do not obliterate the hypertension and tachycardia; surface anesthesia and deeper general anesthesia are more effective.30 Children with previous hypertension display an exaggerated vasopressor response. Sedation and neuromuscular blockade during airway manipulation in infants minimizes the associated bradycardia and systemic hypertension.31-35 The impact of positive pressure ventilation on cardiac performance depends on the underlying disorder (discussed in Chapter 26) but should be carefully considered in preparation for intubation. Laryngoscopy and intubation are potent stimulators of laryngospasm and may cause bronchoconstriction, especially in patients with a history of reactive airway disease. Increased airway resistance probably results from parasympathetic stimulation, with release of acetylcholine and stimulation of muscarinic receptors on airway smooth muscle, especially large central airways. During intubation, oxygen delivery to the patient is commonly interrupted. Ineffective breathing or apnea increases the likelihood of hypoxia, especially in children, with their relatively low functional residual volume and higher basal metabolic rate. Patients with severe pulmonary disease and abnormally low functional reserve capacity are at particular risk.31,34 During apnea, carbon dioxide tension increases at a rate of 3 to 4 mm Hg/min in healthy, sedated adults and probably more rapidly in children, particularly those with severe cardiopulmonary disease or increased metabolic rate resulting from fever, sepsis, or pain.36,37 ICP rises immediately during laryngoscopy even in patients without intracranial pathology before changes in blood gas

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Box 119–3  Recognizing the Difficult Airway History Difficult intubation Upper airway obstruction, current or past, including snoring and sleep apnea Anatomic features Gross macrocephaly Severe obesity Facial asymmetry Facial trauma Midface hypoplasia Airway bleeding Small mouth Oropharyngeal mass Glossoptosis Abnormal soft tissue infiltration Midline clefts or high arched palate Limited temporomandibular joint mobility Micrognathia Nasal obstruction Limited neck mobility Laryngotracheal abnormalities (congenital or acquired)

tensions occur.30,32,38,39 Cerebral metabolic rate and blood flow increase. Hypoxia, hypercarbia, and diminished jugular venous drainage, particularly in struggling patients, contribute further to increases in cerebral blood volume and increased intracranial pressure. Although normally very transient, such intracranial hypertension may predispose patients with coagulopathies or vascular malformations to intracranial hemorrhage. Systemic hypertension in patients with impaired autoregulation of the cerebral circulation (e.g., sick infants or patients with a variety of intracranial disorders) and impedance to jugular venous return by jugular compression, pneumothorax, or coughing and struggling stress both the arterial and venous sides of the cerebral circulation. In patients with poor intracranial compliance, this effect is exaggerated and prolonged. In infants without primary central nervous system disease, muscle paralysis (even without sedation or analgesia) effectively blocks the rise in ICP associated with intubation.34 The systemic hypertensive response is generally unaffected by neuromuscular blocking agents but can be modified by analgesia and sedation or intravenous anesthesia. Patients with severe pulmonary hypertension are at high risk for adverse effects of laryngoscopy. Decreased oxygenation and progressive hypercarbia lead to elevated pulmonary artery pressure. The noxious stimulus of visualizing the airway in itself may precipitate life-threatening hypertension.

Recognition of a Difficult Airway Recognition of a difficult airway is important if potentially lethal surprises in airway management are to be minimized (Box 119-3). Although the intensivist is usually focused on the immediate physiologic disturbances affecting the patient, careful preparation and as thorough an evaluation of each individual patient as is possible is critical. Key components of the history and physical examination, as well as the clinical scenario, can provide insight into potential problem airways. A history of difficult intubations in the past or episodes of upper airway obstruction (including snoring or sleep apnea)

suggest structural abnormalities that may or may not be evident at the moment. Recent tonsillectomy and adenoidectomy, cleft palate repair, or any prolonged surgical procedure resulting in oral edema or bleeding increase the likelihood of difficulty. Examining facial structure is essential, and inspecting the child’s profile is particularly important because significant abnormalities may not be fully apparent on frontal view alone (Figure 119-4). Certain genetic syndromes are associated with craniofacial anomalies, midline defects, or neuromuscular disorders that may make successful intubation via standard techniques exceptionally difficult. Treacher Collins syndrome (mandibulofacial dysostosis), Goldenhar syndrome (oculoauriculovertebral dysplasia), Down syndrome, Pierre Robin syndrome, and the mucopolysaccharidoses, such as Hurler syndrome and Hunter syndrome, are a few of the syndromes that have characteristic features that suggest the high probability of facing a challenging airway. Isolated micrognathia, macroglossia (glossoptosis), facial clefts, midface hypoplasia, prominent upper incisors or maxillary protrusion, facial asymmetry, a high arched narrow palate, a small mouth, and a short, muscular neck or morbid obesity are features that can interfere with effective bag-mask ventilation or visualization of the larynx. Limited temporomandibular joint or cervical spine mobility may make laryngoscopy and tube placement very difficult. Midface instability or upper airway bleeding, edema, airway or neck masses, and foreign bodies are additional reasons for concern.40 Several classification systems assist with recognition and classification of the adult patient with a difficult airway. Although never validated in pediatrics, they provide a useful framework for assessing infants and children. The Mallampati classification (Figure 119-5) assesses visualization of upper airway structures prior to intubation— particularly the uvula, soft palate, and faucial pillars—as a guide to the likely ease of intubation. Mallampati class 1 allows visualization of the uvula, soft palate, and faucial pillars; in class 2, faucial pillars and soft palate are visualized but the uvula is obstructed by the base of the tongue; in class 3 only the soft palate is visualized; and in class 4 the soft palate is not seen. Difficult intubation is more likely associated with classes 3 and 4. This scale can be used with cooperative children, and an approximate evaluation may be obtained by observing many crying infants and young children. The Cormack laryngeal view grade score is shown in Figure 119-5, B. Because the Cormack system requires an attempt to visualize the larynx, it is more valuable as a tool for describing difficulty once it has been encountered than for predicting it. The Cormack score is grade 1, full view of vocal cords and glottis; grade 2, partial view of vocal cords and glottis; grade 3, only the epiglottis is seen; and grade 4, the glottis and epiglottis are not visualized. Grades 3 and 4 predict difficult direct laryngoscopy.41 Although these classification systems are helpful in a controlled environment, particularly the preoperative area of a hospital, they are recognized as having limited utility in the emergent situations often encountered in the ICU, and their ability to predict the degree of difficulty with intubation in children is not well established.42 Ability to visualize the faucial pillars, soft palate, and uvula usually predicts an uncomplicated intubation, but this may be difficult to assess in a sick, uncooperative child.43 Children with severe hypoxia, severe hypovolemia, or other causes of hemodynamic instability, such as intracranial hypertension, a

Chapter 119 — Airway Management

A

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B

Figure 119–4.  Importance of inspecting the patient’s profile. Child with significant micrognathia, not immediately apparent on frontal view. (From Lipton JM, Ellis SR: Diamond-Blackfan anemia: diagnosis, treatment, and molecular pathogenesis, Hematol Oncol Clin North Am 23[2]:261–282, 2009.)

Uvula

Soft palate

Hard palate

Pillars

A

Class 1

Class 2

Vocal cords

B

Grade 1

Class 3

Class 4

Epiglottis

Grade 2

Grade 3

Grade 4

Figure 119–5.  A, Modified Mallampati classification. Class 1: Visualization of the faucial pillars, uvula, soft and hard palate. Class 2: Visualization of complete uvula and palate. Class 3: Visualization of only the base of the uvula and palate. Class 4: Visualization of only the hard palate. B, Cormack and Lehane classification of the laryngeal exposure. Grade 1: Most of the glottis is visible. Grade 2: Only the posterior portion of the glottis visible. Grade III: Only the epiglottis is visible. Grade IV: Not even the epiglottis is visible. (From Amantéa SL, Piva JP, Zanella MI, et al: Rapid airway access, J Pediatr [Rio J] 79[suppl 2]:S127–S138, 2003.)

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Section VII — Environmental Hazards, Trauma, Pharmacology, and Anesthesia Difficult Airway Recognized

Unrecognized

Full Preparation Back-up equipment/ personnel (anesthesiologist, ENT) OR intubation?

Routine drug administration w/ NMB given Unable to intubate

Cooperative

Uncooperative

Awake intubation choices

Sedation/ anesthesia / NMB

Mask ventilation possible? Yes? Non-emergency pathway

No? Emergency pathway

Intubation choices Fail

LMA Effective

Ineffective

Succeed? Yes Confirm

No Succeed

Reverse drugs Awaken

Percutaneous retrograde Seldinger approach Surgical choices

Figure 119–6.  Modification of the American Society of Anesthesiologist’s difficult airway algorithm. (From Practice guidelines for the management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway, Anesthesiology 98:1269, 2003.)

full stomach, or some combination of these conditions, present added difficulties that must be considered. When airway problems are anticipated, the intensivist should approach intubation with a plan specific to the difficulty noted and with a backup strategy in mind.44,45 Extra equipment should be on hand, including a variety of laryngoscope blades, forceps, tubes, bronchoscopes, tracheostomy or cricothyrotomy trays, and additional skilled personnel as needed.46 If sedation is required, agents that can be reversed pharmacologically are desirable and should be titrated slowly to the desired effect. Figure 119-6 shows a modification of the American Society of Anesthesiologist’s difficult airway algorithm and provides an approach to managing the difficult airway.47 A similar plan is necessary at the time of extubation, with serious consideration given to extubation in the operating room or with an airway exchange catheter left in place to facilitate reintubation if necessary.

Process of Intubation All equipment for intubation must be available prior to the procedure (Figure 119-7). A source of suction and appropriate catheters, oxygen and necessary tubing, ventilation bag, mask, laryngoscope and proper-sized blade with a well-functioning light, endotracheal tubes of the expected size and larger and smaller sizes, airway forceps, stylet, and a means of securing the endotracheal tube should be present at the head of the bed so that the intubator does not need to look away from the patient. A functioning intravenous catheter for drug infusion is essential in all but the most extreme emergencies.

Laryngoscope handles are available in standard adult and pediatric sizes. The smaller diameter of the pediatric handle makes it easier to manipulate, particularly when intubating infants and very young children. Blades of many descriptions are available. The most important characteristic is length. Inexperienced operators often select a blade that is too short, making visualization of the larynx difficult. Excessively long blades make it difficult to avoid pressure on the upper lip and teeth. Straight blades provide good exposure in infants and young children. The slightly curved tip of the Miller blade makes visualization of the larynx possible without actually lifting the epiglottis. The broader blade and bore of the WisHipple blade helps displace soft tissues in the young infant’s oropharynx. The Miller No. 2 blade is especially versatile in a broad age group (i.e., children about 3 to 10 years of age). In older children, use of a curved blade is often works best. If a cuffed endotracheal tube is to be used, a curved Macintosh No. 2 or 3 blade is effective in the majority of patients and may provide more room to manipulate a cuff in the oropharynx. Selecting the proper tube size (diameter) is important, both to achieve effective mechanical ventilation and to prevent tracheal injury. A variety of formulas are in use, with the most common being that of Cole: Tube size (inner diameter) = (Age [years]/4) + 4. For infants, no formula is very accurate. Table 119-2 gives reasonable guidelines. Individual differences require that the tube size be modified for each child so that the tube passes easily and allows gas to leak around it at roughly 15 to 30 cm H2O pressure but fits snugly enough to allow delivery of adequate mechanical breaths at a given chest compliance.

Chapter 119 — Airway Management

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D E

A

C K

F

B

J

G

I

H L Figure 119–7.  Equipment for intubation, showing a variety of sizes available for pediatric patients. A, Nasopharyngeal airways. B, Oral airways. C, Masks. D, Anesthesia (Mapleson) bag. E, Laryngoscope handles. F, MacIntosh (curved) and Miller (straight) laryngoscope blades. G, Uncuffed and cuffed endotracheal tubes. H, Endotracheal tube stylets. I, Magill forceps. J, End-tidal CO2 detectors. K, Yankauer suction. L, Tube changer.

Table 119–2  Guidelines for Endotracheal Tube Diameter in Infants and Children Age

Internal Diameter

Orotracheal Length (cm)

Nasotracheal Length (cm)

Premature

2.0–3.0

6–8

7–9

Newborn 3–9 mo

3.0–3.5

9–10

10–11

3.5–4.0

11–12

11–13

9–18 mo

4.0–4.5

12–13

14–15

1.5–3 y

4.5–5.0

12–4

16–17

4–5 y

5.0–5.5

14–16

18–19

6–7 y

5.5–6.0

16–18

19–20

8–10 y

6.0–6.5*

17–19

21–23

11–13 y

6.0–7.0*

18–21

22–25

14–16 y

7.0–7.5*

20–22

24–25

Ideal tube size varies according to age, height, weight, specific airway anatomy, and ventilatory requirements of a child. In general, an air leak around the tube at 15 to 30 cm H2O pressure is desirable. *Cuffed tube.

Traditional teaching has held that use of cuffed endotracheal tubes is not necessary or appropriate in young pediatric patients (younger than 8 years) because the narrow diameter of the trachea at the cricoid ring allows a fairly snug fit without a cuff, and a cuff may make tracheal injury at that level more likely. In addition, the bulk of the cuff usually requires using a tube of 0.5 mm smaller diameter, with the associated increased resistance to gas flow and greater risk of occlusion. Cuffed tubes are routinely recommended for children older than 8 to 10 years because the cricoid ring has been replaced by the triangular opening of the vocal cords as the narrowest point in the airway (see Figure 119-1). In addition, the greater elastic recoil of the lungs and chest wall of older patients may demand higher airway pressures for effective ventilation. However, cuffed tubes of all sizes are available and may be useful in patients in whom consistent minute ventilation is

essential (e.g., in the presence of severely elevated ICP or very reactive pulmonary vasculature) or those requiring relatively high airway pressures. Although data are limited, evidence is growing that cuffed tubes can be used in young children without higher incidence of airway complications.48-52 The modern low-pressure, high-volume cuff requires a much lower pressure to obtain a seal than did the endotracheal tube cuffs of the past. When a cuffed tube is used, great care should be taken to inflate it with the “minimum occlusive volume,” the minimum volume required to “just seal” the gas leak around the tube during mechanical inspiration and prevent mucosal ischemia and subsequent tracheal damage. Potential advantages of cuffed tubes include decreased likelihood of multiple intubations to identify the correct size and avoidance of changing the endotracheal tube of a critically unstable patient if lung disease worsens. In addition, absence of a significant leak around the endotracheal tube (ETT) may decrease the likelihood of flow-triggered ventilator autocycling. The ability to occlude the leak also facilitates pulmonary function testing and indirect calorimetry.

Pharmacologic Agents Facilitating ­Intubation Although intubation often is possible without use of drugs, the physiologic and psychological benefits of their use usually outweigh the disadvantages.53,54 Analysis of data in the pediatric National Emergency Airway Registry shows that intubation success rate is higher when both sedation and neuromuscular blockade are used.55 This finding is equally true in neonates, in whom sedation and neuromuscular blockade are still commonly not used, with no evidence they are harmful.56 In neonates the predominance of evidence indicates that use of neuromuscular blockade is associated with a lower risk of intracranial hemorrhage and pulmonary airleak.57 Excellent technical airway skills are an absolute prerequisite, however, because loss of control of the airway invites catastrophe. Drugs facilitating intubation are listed in Table 119-3.

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Table 119–3  Drugs Facilitating Intubation Drugs

Dose

Duration

Comments

INTRAVENOUS ANESTHETICS Thiopental

4–7 mg/kg IV

5–10 min

Anesthesia, apnea, myocardial depression, decreased venous tone, ↓ CMRo2, ↓ CBF, ↓ ICP, ↓ IOP

Etomidate

0.3 mg/kg IV

3–5 min

Anesthesia, adrenal suppression (↑mortality in sepsis?), minimal CV effect, apnea, ↓ CMRo2, ↓ CBF, ↓ ICP

Ketamine*

1–2 mg/kg IV; 4–6 mg/kg IM

10–15 min

Anesthesia, ↑ systemic arterial pressure, ↑ HR, ↑ ICP, ↑ IOP, ­hallucinations, laryngospasm, bronchodilation

Propofol

1–3.5 mg/kg IV, then 0.05–0.3 mg/kg/min

10–15 min

↓ Systemic arterial pressure, ↓ CMRo2, ↓ CBF, ↓ ICP, metabolic acidosis

30–90 min

Analgesia, respiratory depression, cardiovascular stability, occasional bradycardia, or chest wall rigidity

SEDATIVES/ANALGESICS Fentanyl*

2–5 μg/kg IV

Remifentanil

1–3 μg/kg, then 0.25–1 μg/kg/min

Morphine*

0.1–0.2 mg/kg IV

2–4 h

Analgesia, respiratory depression, ↓ systemic arterial and venous tone, ↓ systemic blood pressure

Midazolam*

0.1–0.3 mg/kg IV

1–2 h

Amnesia, sedation or euphoria, ± cardiovascular stability, occasional respiratory depression

Lorazepam

0.1–0.3 mg/kg IV

2–4 h

Sedation, anxiolysis, minimal cardiovascular effect

Analgesia, respiratory depression, cardiovascular stability

NEUROMUSCULAR BLOCKING AGENTS Rocuronium*

0.6–1.2 mg/kg IV

15–45 min

Minimal cardiovascular effect, prolonged duration in liver failure

Vecuronium*

0.1–0.3 mg/kg IV

30–75 min

Minimal cardiovascular effect, prolonged effect in hepatic failure

Cis-atracurium

0.1 mg/kg, then 1–5 mg/kg/min

20–35 min

Metabolized by plasma hydrolysis, mild histamine release

Atracurium

0.5 mg/kg

30–40 min

Metabolized by plasma hydrolysis, mild histamine release

Succinylcholine*

1–4 mg/kg IV

5–10 min

↓ HR, K+ release in neuromuscular disease, trauma or burns, masseter spasm, malignant hyperthermia, myoglobinuria

Duration of effect is only approximate and varies with age and physiologic state of the patient. *Agents may be given intramuscularly but will have slower onset and more variable duration of effect. CBF, Cerebral blood flow; CMRo2, cerebral metabolic oxygen requirement; CV, cardiovascular; HR, heart rate; ICP, intracranial pressure; IM, intramuscular; IOP, intraocular pressure; IV, intravenous.

Anticholinergic Agents Anticholinergic agents decrease oral secretions and prevent bradycardia, particularly in young infants, although their use is not universally recommended. Atropine (0.02 mg/kg) and glycopyrrolate (0.01 mg/kg intravenously) are both effective. Scopolamine provides amnesia, decreases secretions, and prevents bradycardia. The drying effect commonly requires approximately 15 to 30 minutes and is rarely achieved in emergency intubation.

Sedative and Analgesic Agents Most patients benefit from some degree of sedation. Drugs commonly used include intravenous anesthetic agents, anxiolytic agents, and narcotic analgesics. The appropriate choice in a particular patient depends on the child’s hemodynamic status, level of anxiety, and underlying disease process. Thiopental is a short-acting barbiturate that can provide deep anesthesia, obliterating awareness of the intubation process. It decreases cerebral oxygen consumption and thereby sharply lowers cerebral blood flow (CBF) and ICP. However, it is also a potent myocardial depressant; it decreases peripheral vascular resistance and may precipitate cardiovascular collapse in

patients with myocardial dysfunction or hypovolemia. At anesthetic doses (4 to 7 mg/kg), it reliably causes apnea. Etomidate is another short-acting intravenous anesthetic that causes rapid loss of consciousness (at 0.3 mg/kg) and respiratory depression, although it is less potent than thiopental. It also decreases cerebral oxygen consumption, CBF, and ICP, but without significant detrimental effects on cardiovascular function and with less respiratory depression than thiopental. These characteristics have led to its increased use for emergency intubation.58,59 It has no analgesic properties and may be best combined with a narcotic analgesic. Adverse effects include vomiting, myoclonus, and lowering of the seizure threshold. With continuous infusion for sedation, it can cause adrenal insufficiency, making it inappropriate for longterm use in the ICU.60 Growing evidence suggests it may suppress adrenal function even after a single dose, particularly in patients with sepsis and shock, raising questions about its use in these settings.61-70 Ketamine is another potent nonnarcotic analgesic and anesthetic that has been used safely in children in the critical care setting.71,72 It increases heart rate, systemic blood pressure, and cardiac output and is a fairly potent bronchodilator. However, myocardial depression may be apparent after

Chapter 119 — Airway Management

administration to patients with catecholamine depletion. It may be of particular value in patients with status asthmaticus or other reasons for bronchospasm and may have a beneficial effect in sepsis. Spontaneous ventilation is preserved in most patients, but laryngospasm may occur.73 Although in the past it has been considered inappropriate for patients with intracranial hypertension because of evidence that it increases cerebral metabolic rate, blood flow, and ICP, more recent studies indicate that it may be used safely in these patients, although no clear consensus has emerged.74 Emergence delirium and hallucinations occur frequently and may be prolonged and recurrent, particularly in adolescents and young adults. Use of ketamine for a variety of procedures in children has been successful, with little reported difficulty with neuropsychiatric complications, but follow-up in most studies has been short and superficial.75-80 Whereas the majority of patients do not suffer severe disturbances, those who do may have severe and prolonged distress. Benzodiazepines or barbiturates may decrease the incidence and severity of such adverse effects and the incidence of vomiting, although the data in children are limited and conflicting.75,81,82 Propofol is an ultra-short-acting agent with rapid onset and offset unless given by continuous infusion. It causes respiratory depression, desaturation, and systemic hypotension secondary to its negative inotropic effects and peripheral venous and arterial vasodilation. Its role in airway management of critically ill children is limited because of these effects. It has gained widespread acceptance as an anesthetic agent in children, however, and has been used extensively for procedural sedation.83,84 Use in the ICU for more than approximately 6 hours is not recommended because of its still unexplained association with metabolic acidosis, cardiovascular collapse and death, propofol syndrome, among pediatric ICU patients.85-87 Current labeling warns against its use for prolonged sedation in children. The benzodiazepines, including diazepam and midazolam, relieve anxiety, produce sedation in most children, and provide amnesia for noxious procedures. They do not relieve pain. They have relatively little hemodynamic effect in most patients and rarely interfere with spontaneous breathing at therapeutic doses. Although they decrease cerebral oxygen consumption, their effect on cerebral metabolism is much less pronounced than that of thiopental. They are best combined with a narcotic analgesic when used for intubation in order to decrease the discomfort and pain associated with laryngoscopy and passage of the tube. Narcotics commonly used for intensive care include morphine, fentanyl, and some of the ultra-short-acting agents such as remifentanil. They cause respiratory depression in a dose-dependent fashion and increase intracranial blood flow in proportion to the increase in Paco2. If hypercarbia is prevented, they decrease cerebral metabolic rate and blood flow. In the setting of altered cerebral autoregulation, they may not protect the patient from alterations of CBF.88,89 Morphine causes histamine release and peripheral vasodilation and may precipitate systemic hypotension. Fentanyl is approximately 100 times more potent than morphine but does not release histamine and has little hemodynamic effect, even at anesthetic doses. Large doses given rapidly can cause bradycardia or chest wall rigidity. Remifentanil is a rapid-onset, ultrashort-acting opiate that is even more potent than fentanyl and may have potential benefit in intubation for procedures.

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Neuromuscular Blocking Agents Neuromuscular blocking agents cause reversible paralysis, facilitating visualization of the airway and insertion of the endotracheal tube in an atraumatic fashion. Most drugs in use are nondepolarizing relaxants with very similar action. Differences are primarily in their hemodynamic effects, metabolism, and excretion.90,91 Vecuronium and rocuronium are the agents most commonly used. Both are amino-steroid agents. Vecuronium has virtually no hemodynamic effect. Its duration of action varies depending on the patient’s age, approximately 70 minutes in infants and 35 minutes in older children. It is metabolized exclusively by the liver. Rocuronium provides good intubating conditions nearly as rapidly as succinylcholine (in about 45 to 90 seconds)92-94 without the adverse effects. Its duration is longer at 15 to 45 minutes (and longer in infants).95-97 Like vecuronium, it has minimal hemodynamic effect, is metabolized by the liver, and largely is excreted in bile (with a small amount excreted by the kidneys). Atracurium and cis-atracurium, both benzylquinolinium agents, also have minimal hemodynamic effects in most patients but may cause histamine release and hypotension in some persons. Metabolism occurs by spontaneous plasma hydrolysis; thus neither renal nor hepatic function is necessary for elimination. Its duration of action is short at about 15 to 20 minutes. The only depolarizing relaxant in clinical use is succinylcholine. Its only advantage is its rapid onset of action (45 to 60 seconds) and brief duration of action (5 to 10 minutes). Muscle fasciculations occur at the onset of action in patients older than 4 years and may increase intracranial, intraocular, and intragastric pressure. Defasciculating doses of a nondepolarizing neuromuscular blocker prior to succinylcholine administration minimize such effects. Massive hyperkalemia may occur following its use in patients with spinal cord injury, severe burns, crush injuries, or neuromuscular disease. More recently, the spread of acetylcholine receptors outside of the neuromuscular junction, the mechanism presumed to underlie the massive hyperkalemic response previously noted, has been recognized to occur in many forms of critical illness associated with immobility, placing many critically ill patients at risk.98 It is a known trigger for malignant hyperthermia and frequently causes myoglobinuria in otherwise healthy children. The U.S. Food and Drug Administration has issued a warning against its use for routine intubation in children because of these complications. Although it is frequently used for emergency intubations and is widely recommended,54,99,100 the difference in time to conditions for intubation between succinylcholine and rocuronium is small (∼30 seconds), very rarely of clinical significance, and inadequate to justify the added risk in the vast majority of cases. Moreover, the time to critical hemoglobin desaturation in the case of a failed airway is shorter than its duration of action, especially in children, so its shorter duration of action does not provide a meaningful advantage over nondepolarizing blockers.101 A more extensive discussion of anesthetic agents and their use is given in Chapters 122, 123, and 124.

Orotracheal Intubation When all equipment is ready, an assistant is assigned to monitor the child’s color, heart rate, blood pressure, and oxygen saturation and to administer drugs when ordered. The child

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is placed supine with the head in the “sniffing” position. The infant’s large occipitofrontal diameter naturally results in good position most of the time, but a small pad under the shoulders may be helpful. In older children, a thin pad under the occiput helps establish slight neck flexion (Figure 1198). The head is extended to align the oral, pharyngeal, and laryngeal axes as much as possible. Spontaneous or manual ventilation with supplemental oxygen is maintained as drugs to facilitate intubation are given. Many patients requiring emergency intubation have severely impaired gas exchange and may require several minutes of breathing 100% oxygen, often with positive inspiratory and end expiratory pressure.102 Applying cricoid pressure during manual ventilation helps minimize gastric distension by air (Figure 119-9).103 After the drugs take effect, the pharynx is suctioned and stomach contents are aspirated. The patient is again briefly oxygenated, and the mask is removed. In a fully relaxed patient in good position, the mouth falls open. It can be opened more widely with caudad pressure on the chin by the intubator’s left fifth finger as the laryngoscope is introduced into the righthand corner of the mouth. In an unsedated patient or when the mouth opens abnormally, it may be necessary to open the jaw with the often recommended scissorlike use of the right thumb and forefinger, but this action places the intubator at risk of both trauma and infection and should be avoided when possible. The laryngoscope is gently advanced into the pharynx and leftward, sweeping the tongue out of the way. Holding the handle at a 45-degree angle to the bed and lifting along the line of the handle to avoid pressure on the lips, teeth, or alveolar ridge, the intubator displaces the mandible until the vocal cords are in view (Figure 119-10). Application of gentle cricoid pressure by an assistant may be helpful. Once the larynx is clearly visualized, the tube is advanced from the right corner of the mouth into the larynx (not through or along the blade itself). The nearly universal tendency to plumb the depths of the child’s airway with extra centimeters of tube results in main stem intubation. Unfortunately, the recommendation to use three times the ETT size for appropriate depth of tube placement for a child results in malposition in 15% to 25% of patients.104 Placement is likely to be better if the intubator is

careful to place the appropriate markings near the tip of the endotracheal tube at the level of the cords. If such markings are absent, careful attention to advancing the tip of the tube only a few centimeters (2 to 4 cm) beyond the cords prevents main stem intubation. O P

P

L

O

L

A O P L

B

D O P L

E P O L

C

L

P

O

F

Figure 119–8.  A, Positioning of the young child and infant for laryngoscopy and tracheal intubation. B, Placing the child’s head on a thin pad flexes the neck slightly and helps align the pharyngeal and laryngeal axes. C, Extension of the atlantooccipital joint (into the sniffing position) further aligns the oral axis with the pharyngeal and laryngeal axes. D, Before the age of approximately 3 years, the child’s large frontal occipital diameter makes the pad beneath the head unnecessary, but a small pad under the shoulders (E) may improve alignment of the pharyngeal and laryngeal axes. F, As with the older child, head extension improves alignment of the oral, pharyngeal, and laryngeal axes. (From McAllister JD, Gnauck KA: Rapid sequence intubation of the padiatric patient. Fundamentals of practice, Emerg Med 46:1249 –1284,1999.)

Cricoid cartilage

Esophagus Figure 119–9.  Sellick maneuver. Pressure on the cricoid cartilage occludes the esophagus or hypopharynx.

Chapter 119 — Airway Management

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Epiglottis

Base of the tongue

Larynx

Vestibular fold

Vocal cords

Arytenoids

Esophagus

Figure 119–10.  Glottic area view via laryngoscopy.

With the tube in place, the child again receives manual ventilation with oxygen, and the presence of an appropriate leak is documented. Correct tracheal placement of the tube is suggested by observation of moisture condensing in the tube, good chest excursion, symmetrical breath sounds, and effective oxygenation. The most reliable means of ensuring proper placement, following clear visualization of the tube passing between the vocal cords, is documentation of carbon dioxide in expired gas (by capnometry or a disposable CO2 detector). Only in the settings of full cardiac arrest or extremely low pulmonary blood flow can the endotracheal tube be in the airway without detection of expired carbon dioxide. Under other conditions, malposition of the tube, most commonly in the esophagus, must be assumed. It is important to remember that capnometry does not ensure correct positioning within the airway: carbon dioxide will be detected with the tube anywhere from a bronchus to above the vocal cords. Documenting location of the tip of the tube between the thoracic inlet and T4 on chest radiograph, with the head in a neutral position, is important. (The tip will descend deeper into the trachea with neck flexion and move upward with neck extension.105,106 With the endotracheal tube in good position an inflated cuff often can be palpated at the sternal notch when quick pressure is applied to the sentinel balloon. The tube is secured, avoiding pressure on the lips, particularly at the angle of the mouth, and keeping the vermilion border of the lip free of tape.

Nasotracheal Intubation If nasotracheal intubation is preferred, it should generally follow orotracheal intubation so that an assistant can ventilate the child while the somewhat more difficult intubation is accomplished. A topical vasoconstricting agent such as phenylephrine 0.25% or oxymetazoline 0.05%, sprayed into the nasal fossa, minimizes the risk of bleeding. In most children a tube of the same diameter as the oral tube can be gently advanced along the floor of the nasal cavity, essentially directly posteriorly, into the nasopharynx with firm, but not brutal, pressure. With the oral tube in the left corner of the mouth, the laryngoscope is again advanced into the pharynx until the oral tube is visualized passing through the cords and the tip of the nasal tube is seen in the nasopharynx. The nasal tube is advanced until it lies directly above the cords,

anterior to the oral tube. Use of Magill forceps may facilitate this maneuver. When the nasal tube is in good position to enter the larynx, the assistant removes the oral tube and helps advance the nasal tube. Difficulty advancing the tube after it has passed the vocal cords may be overcome by rotating the tube or flexing the neck. The tube then is secured; pressure on the septum or anterior rim of the nares should be avoided. Although an orotracheal tube usually is placed more rapidly in emergencies, it often stimulates gagging, makes mouth care difficult, and it is more easily kinked or bitten. Anchoring the tube often is difficult because of saliva, and tongue movement may contribute to palatal or tracheal erosion and increase the likelihood of accidental extubation. Trauma to lips, teeth, tongue, and other oropharyngeal structures may occur. Nasotracheal intubation is more comfortable for most conscious patients, causes less stimulation of the gag reflex, is more easily secured, and prevents the problem of biting in patients with seizures, decerebrate rigidity, or extreme agitation. However, bleeding, adenoid injury, sinusitis, and trauma to the nasal turbinates, septum, or nares may occur with nasotracheal intubation, and the risk of sinusitis is greater than with orotracheal tubes.107,108 Contraindications to nasotracheal intubation include coagulopathy, maxillofacial trauma, CSF leak, and basilar skull fracture.

Videolaryngoscopy Videolaryngoscopy allows visualization of the larynx without requiring a direct line of sight aligning the oral, pharyngeal, and tracheal axes. In the setting of a difficult airway, video assistance improves visualization and more rapid intubation in adults. Visualization in children is also improved, but experience published to date suggests that the first-pass success rate is lower and time to intubation is longer than with direct laryngoscopy, at least in patients in whom airway visualization is only moderately difficult.109,110 On the other hand, studies of simulated difficult airway management in infants have shown improved intubation rates without a longer time to intubation.111 At present, it appears that these devices may be most valuable in very difficult situations, including cervical spine instability and craniofacial abnormalities, rather than as an advance in routine laryngoscopy.112

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Section VII — Environmental Hazards, Trauma, Pharmacology, and Anesthesia

The videolaryngoscope also provides a useful opportunity for teaching airway skills. A duplicate video image allows an instructor to view the attempted intubation in real time and provide immediate guidance and evaluation.

Table 119–4  Threshold Values for Low (≤10%) and High (≥25%) Risk of Extubation Failure Low-Risk Value (≤10%)

High-Risk Value (≥25%)

Vtspon (mL/kg)

≥6.5

≤3.5

Fio2

≤0.30

>0.40

Paw (cm H2O)

<5

>8.5

OI

≤1.4

>4.5

FrVe (%)

≤20

≥30

Variable

Flexible Fiberoptic Bronchoscopy Flexible fiberoptic bronchoscopy is an effective means of securing a difficult airway, especially in patients with cervical spine instability or those in whom limited jaw mobility or oropharyngeal lesions prevent good visualization of the larynx.40,45,113 Assuming the operator’s clinical proficiency, the procedure almost always is successful, with little or no trauma to the patient. The nasal route is routinely chosen because it is easier to use, better tolerated, and safer for the instrument than other routes. A topical vasoconstrictive agent and local anesthetic are applied to the nasal mucosa. The endotracheal tube is advanced through the nose into the nasopharynx, and the flexible scope is threaded through it. The scope is advanced through the vocal cords, and the tube is passed over it into the trachea. (Alternatively, the tube with its connector removed may be threaded retrograde over the scope. The scope is advanced through the nose, to the nasopharynx, and through the larynx into the trachea. The endotracheal tube is advanced over the bronchoscope into good position.) The bronchoscopist then visualizes and secures the position of the tube in the trachea and carefully withdraws the scope.

Extubation Extubation is appropriate when the conditions for intubation are no longer present. In general, this means that the work of breathing has decreased to a level manageable by the patient. In most cases, this situation occurs when oxygenation is adequate with the administration of 40% oxygen or less; spontaneous tidal volume is greater than 3.5 mL/kg; the patient can sustain a normal Paco2 without mechanical breaths with a near normal respiratory rate for age and without the use of accessory muscles; secretions are manageable; upper airway reflexes are intact; and neuromuscular function is sufficiently good to achieve an adequate vital capacity and maximum inspiratory pressure (Table 119-4).114 Although standard teaching holds that extubation is most likely to be successful when there is an air leak around the ETT at less than 30 cm H2O, recent study indicates that the presence or absence of a leak is a poor predictor of the success of extubation.115 If intubation was for relief of upper airway obstruction, direct inspection revealing more normal anatomy is of particular value, and the significance of a leak may be greater. In patients with a previously difficult to manage airway, extubation over a tube changer or in the operating room, with surgical support available, should be considered.116 Before extubation, the child is given nothing by mouth for 4 to 6 hours. The tube and pharynx are suctioned thoroughly, and the child is ventilated with 100% oxygen to provide a reservoir of oxygen as a buffer against laryngospasm at extubation. With the lungs fully inflated, the endotracheal tube is removed, and the child is provided with humidified oxygen and observed closely. Postextubation stridor is common and may range from mild to life-threatening. Children younger than 4 years are most frequently affected by postextubation stridor. Factors

PIP (cm H2O)

≤25

≥30

Cdyn (mL/kg/cm H2O)

≥0.9

<0.4

Vt/Ti (mL/kg/sec)

≥14

≤8

Cdyn, Dynamic compliance; Fio2, fraction of inspired oxygen; FrVe, fraction of total minute ventilation provided by the ventilator; OI, oxygenation index; PIP, peak ventilatory inspiratory pressure; Vtspont, spontaneous tidal volume indexed to body weight; Vt/Ti, mean inspiratory flow. From Venkataraman ST, Khan N, Brown A: Validation of predictors of extubation success and failure in mechanically ventilated infants and children, Crit Care Med 282:991, 2000.

contributing to airway edema include a tight endotracheal tube or cuff, traumatic or repeated intubations, excessive movement of the tube (or patient), preexistent airway abnormalities, and airway infection.117 Cool mist or humidified oxygen is sufficient treatment for children with mild symptoms. Nebulized racemic epinephrine (0.5 mL of a 2.25% solution in 2.5 mL of saline solution delivered intermittently or continuously) effectively relieves more severe upper airway obstruction in most children, probably by local vasoconstriction. Only the l-isomer in the racemic formulation is biologically active. Epinephrine available for cardiovascular use is as safe, effective, and less expensive if half the racemic dose is used. Following its use, edema may recur, so close observation must continue. The value of corticosteroids is more controversial, in part because most studies do not differentiate multiple causes of croup.118-120 Patients at high risk for post-extubation stridor (e.g., those with multiple intubation attempts) appear most likely to benefit.121-123 Dexamethasone (0.3 to 0.5 mg/kg every 6 hours for 1 or 2 days) is recommended in selected cases. The work of breathing through a narrowed upper airway can be decreased by inhalation of a low-density gas mixture. Oxygen in helium is less dense than air or pure oxygen and permits higher inspiratory flow at lower resistance. Heliumoxygen mixtures are commercially available, usually providing 20% oxygen in 80% helium. More oxygen can be added to the mix as needed. Although traditional teaching holds that at least 70% helium is necessary to decrease airway resistance enough to make a clinical difference in the work of breathing, experience demonstrates value at considerably lower concentrations. If pharmacologic treatment is ineffective, noninvasive ventilatory support may be useful in preventing the need for reintubation, but meticulous attention to the patient’s work of breathing is critical to recognize potential catastrophic airway obstruction. Reintubation with a smaller tube for 12 to 24 hours may be necessary, and continued dexamethasone treatment and sedation to minimize agitation and further trauma to the airway may permit resolution of symptoms. Persistent symptoms are an indication for diagnostic laryngotracheobronchoscopy.

Chapter 119 — Airway Management

Complications of Endotracheal Intubation Complications of intubation can be divided into those related to placement of the artificial airway, those that occur while the endotracheal tube is in place, and those related to extubation or appearing late (Table 119-5). Immediate complications usually are related to the underlying disease process, the physiologic effects of laryngoscopy and intubation, or direct trauma to airway structures. The child’s general condition, tube size, cuff pressure, movement, airway infection, systemic perfusion, duration of intubation, and attention to meticulous airway care are factors influencing the development of problems during maintenance of the airway.124 Laryngospasm, aspiration, and failure (or inability) to deflate a cuff cause complications at extubation. Although laryngeal or tracheal injury may be obvious at the time of intubation, symptoms may be delayed 2 to 6 weeks.

Prolonged Intubation The safe duration of endotracheal intubation in infants and children is not clear. Since the 1950s, the accepted period has increased from less than 12 hours to an undefined much longer period. Subglottic stenosis is reported to occur in 1% to

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8% of infants after prolonged intubation, but a similar incidence has been noted after intubation for less than 1 week.125 In older infants, children, and adults, it is becoming clear that there is no clear “safe” period. Complications can occur immediately at intubation or may not be seen after many weeks or even months with an endotracheal tube in place.126 The decision to switch to tracheostomy should not be based on an arbitrary time limit but rather on the relative advantages and disadvantages of one artificial airway over another in each individual patient.

Special Circumstances Full Stomach

Patients with a full stomach are at high risk for aspiration of gastric contents during airway manipulation, particularly if protective airway reflexes are impaired. Much of the morbidity associated with aspiration can be attributed to the effects of acid aspiration. Aspiration of fluid with a pH below 1.8 is associated with a very high incidence of severe pulmonary dysfunction and death. Aspiration of fluid with a pH between 1.8 and 2.5 produces symptoms of moderate severity. When fluid with a pH above 2.5 is aspirated, sequelae are less a consequence of the acid than of other characteristics of the material

Table 119–5  Complications of Endotracheal Intubation Immediate

Maintenance

Extubation/Late

Hemodynamic instability

Obstruction

Laryngospasm

Dysrhythmias

Sinusitis

Gagging, vomiting

Apnea

Otitis (similar to immediate)

Aspiration

PHYSIOLOGIC

↓ Pao2

Sore throat

↑ Paco2

Dysphonia, aphonia

Coughing Laryngospasm Gagging, vomiting, regurgitation, aspiration ↑ Intracranial pressure ↑ Intraocular pressure TRAUMATIC Nasal septum laceration, perforation

Lip, tongue ulceration

Laryngeal or tracheal granuloma

Nasal turbinate injury

Nares ulceration

Vocal cord paralysis

Tooth loss or injury

Palatal erosion, cleft formation

Subglottic stenosis

Lip, tongue, palate laceration, hematoma

Vocal cord edema, ulceration

Tonsillar or adenoid avulsion, laceration, ­hematoma

Laryngeal and tracheal mucosal ischemia, ­ulceration, necrosis

Laryngeal strictures

Recurrent laryngeal nerve damage

Cervical spine subluxation

Subglottic edema, ulceration

ESOPHAGEAL POSITION Malposition Esophageal

Mainstem intubation

Mainstem bronchus

Inadvertent extubation

Intracranial

Atelectasis

Soft tissue

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aspirated.127 Other risk factors include the volume aspirated, the presence and nature of particulate food particles, contamination by bacterial pathogens, underlying pulmonary or systemic disease, and immunosuppression.128 Food particles may physically obstruct small or even large central airways, with the expected alterations in lung volume in segments distal to the obstruction. In addition, certain foods may cause severe local inflammatory changes. Bacterial contamination of the upper gastrointestinal tract secondary to bowel obstruction or even antacid administration greatly increases the risks of respiratory infection following aspiration. Patients who have eaten shortly before intubation (<6 hours) should be assumed to have a full stomach. In addition, those with bowel obstruction, pharyngeal or upper gastrointestinal bleeding, trauma, or acute onset of illness within 6 hours of eating and those who are pregnant or who have ileus or tense abdominal distension from any cause should be considered to have a full stomach. Although delaying airway manipulation might be the measure most certain to prevent aspiration, such an approach is not a realistic option in most situations confronting the intensivist. In a conscious child, the volume of gastric contents can be minimized by suction through a relatively large-gauge nasogastric tube, but complete emptying of the stomach, particularly of large food particles and blood clots, is rarely possible. Although H2 antagonists such as famotidine or ranitidine effectively decrease both the volume and acid content of gastric secretions, an adequate effect requires 60 to 90 minutes following administration of these agents. Neither antacid nor H2 blockers decrease the volume of gastric contents already present in the stomach. Anticholinergic agents such as atropine or glycopyrrolate also reduce gastric acidity but slowly and less effectively than the H2 antagonists. In addition, they may decrease gastroesophageal sphincter tone and appear to have no value in preventing the acid aspiration syndrome. Antacids can effectively neutralize gastric pH. However, when aspirated, particulate antacids (aluminum and magnesium hydroxides) produce inflammatory changes as severe as gastric acid and food particles. Clear antacids, such as sodium citrate or Alka-Seltzer, appear to provide true protection. They effectively increase gastric pH and, when aspirated, appear to produce damage no more severe than that caused by normal saline solution. However, their use has not become common clinical practice. Intubation is at once protective of the patient vulnerable to gastric aspiration and itself a risk to the patient. In an alert child with intact protective airway reflexes, it may be appropriate to pass a nasogastric tube to decrease the volume of gastric contents. A clear antacid (e.g., sodium citrate, 10 to 30 mL) can be administered orally or through the tube, which then is removed. In a child with impaired reflexes, no effort to pass a nasogastric tube should be made because of the risk of inducing vomiting or regurgitation with subsequent aspiration. The intensivist should examine the patient’s airway to be as certain as possible that intubation will not be difficult, as discussed previously. If intubation likely will be straightforward, a rapid-sequence intubation is indicated (Box 119-4). The goal of this method of intubation is to minimize the likelihood of vomiting or regurgitation and the time between loss of protective reflexes and correct positioning of the endotracheal tube. The sequence consists of preoxygenation, administration of an intravenous sedative or anesthetic with immediate cricoid

pressure, pharmacologic paralysis, and endotracheal intubation. Properly applied, cricoid pressure probably decreases the likelihood of insufflation of gas into the stomach or regurgitation of gastric contents into the trachea and may improve visualization of the larynx (see Figure 119-9).103,129-131 On the other hand, excessive pressure may actually increase the likelihood of vomiting, occlude the trachea, or make visualization more difficult. The patient spontaneously breathes 100% oxygen by mask for 3 to 5 minutes before further manipulation. If the child can cooperate and has relatively normal gas exchange, four deep breaths provides a reasonable pulmonary reservoir of oxygen. However, in patients with severe pulmonary parenchymal disease, improvement in oxygenation may be limited and require a longer period of oxygenation.132 If other factors in the child’s condition permit, next steps in the rapid sequence intubation should be delayed until hemoglobin saturation reaches 100% or oxygenation reaches a plateau. Once preoxygenation is complete, the anesthetic or sedative is administered by rapid intravenous infusion, cricoid pressure is applied immediately by an assistant, and, as consciousness is lost, a muscle relaxant is given. The mask supplying oxygen is kept in place until the patient becomes apneic, but no effort to assist ventilation is made in order to avoid gastric distension and regurgitation. Once the patient is flaccid and apneic, the intensivist performs laryngoscopy and intubates the patient. Using a stylet in the endotracheal tube facilitates rapid intubation. Only after correct tube position is verified and the tube cuff, if present, is inflated should cricoid pressure be relieved and manual ventilation begun. In the case of unexpected difficulty intubating the patient and evidence of progressive hypoxemia, manual ventilation between attempts may be necessary but should be done with continued cricoid pressure.

Box 119–4  Rapid-Sequence Intubation for Full Stomach Indications Food intake <4–6 hours before intubation Pharyngeal or upper gastrointestinal bleeding Intestinal obstruction or ileus (includes acute onset of illness) Tense abdominal distension Pregnancy Relative contraindications “Difficult” airway Profuse hemorrhage obscuring visualization Upper airway obstruction Increased intracranial pressure Procedure Prepare all necessary equipment, including suction devices Allow patient to breathe 100% oxygen for 3 minutes Direct assistant to apply cricoid pressure Rapid intravenous infusion of anesthetic or sedative/analgesic and neuromuscular blocking agents Allow patient to continue to breathe oxygen until apneic Avoid manual ventilation to minimize gastric distension Perform laryngoscopy and orotracheal intubation with stylet in endotracheal tube Confirm endotracheal tube placement Release cricoid pressure

Chapter 119 — Airway Management

The “classic” combination of drugs used for rapid sequence induction/intubation is sodium thiopental (4 to 6 mg/kg) and succinylcholine (1 to 4 mg/kg) with a prior defasciculating dose of a nondepolarizing muscle relaxant such as vecuronium. In hemodynamically unstable patients, alternative drugs include ketamine or a benzodiazepine alone or in combination with a short-acting narcotic. As previously discussed, etomidate has been a popular agent, but growing evidence suggests its use is inappropriate in patients with shock, especially with presumed sepsis. Succinylcholine has multiple undesirable adverse effects (as noted previously) that may include increased intragastric pressure. Most of the nondepolarizing relaxants, when given in amounts two to three times the usual intubating dose, produce good conditions for intubation nearly as quickly as does succinylcholine (60 to 90 seconds) and without adverse effects but lasting longer. Rocuronium is the current best alternative, with its rapid onset and short duration of action. Table 119-3 lists suggested drugs and doses.

Increased Intracranial Pressure and Neurologic Dysfunction The intensivist is frequently called upon to intubate ­children with severe central nervous system dysfunction resulting from infection, hemorrhage, trauma, hydrocephalus, or mass lesions, any of which may be associated with actual or ­imminent intracranial hypertension and herniation. The pathophysiology of such disorders is discussed in depth in Section IV. In most circumstances the intensivist can observe signs of elevated ICP or recognize settings where the likelihood is high, but there is no clinical measure of its severity. Current guidelines recommend intubation for patients with a Glasgow Coma Scale score of 8 or less.133 Intubation under these conditions should be undertaken with the recognition that it is a likely stimulus for further and potentially lethal intracranial hypertension. The most immediate means of lowering ICP involves decreasing CBF (volume) through hyperventilation. Unfortunately, the process of intubation likely will decrease minute ventilation and increase cerebral blood volume for this and other reasons, as previously discussed. Under normal circumstances, CBF is closely coupled to the cerebral metabolic oxygen requirement (CMRo2). Cerebral oxygen consumption and blood flow increase with increasing body temperature, motor activity, pain or other noxious stimuli, and seizure activity. Blood flow also increases rapidly when Pao2 falls below 50 to 60 mm Hg and linearly as Paco2 increases over a wide range. With intact autoregulation, blood flow is independent of systemic blood pressure except at very high or low levels, but when autoregulation is impaired, mean arterial pressure may affect CBF over a much broader range. Elevated intrathoracic pressure during struggling, coughing, or Valsalva maneuvers may impede jugular venous drainage and result in intracranial venous congestion. Laryngoscopy and intubation are powerful noxious stimuli. In the awake unsedated child and even in the severely obtunded patient, laryngoscopy and intubation likely will precipitate vigorous struggle, coughing, pain (anxiety), and marked evidence of autonomic stimulation.25,38,39,134 In most patients, sympathetic discharge predominates with tachycardia, hypertension, and diaphoresis. In the infant, vagal stimulation often predominates with resulting bradycardia.

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Even in the lightly anesthetized patient, laryngoscopy itself and then intubation are associated with hypertension, tachycardia, and increased ICP. As might be predicted, massive surges in ICP are more likely to occur in patients suspected of having borderline or high baseline ICP before intubation than in those with intracranial pathology with well-compensated or previously controlled pressure. Arterial hypertension may precipitate further hemorrhage in the child with a vascular malformation, coagulopathy, or bleeding into a tumor. ICP waves may reduce cerebral perfusion pressure to ischemic levels or cause frank herniation. Given the risk of life-threatening systemic and intracranial hypertension in these patients, it is clear that laryngoscopy and intubation should be undertaken with every effort to minimize stimulation and associated struggle.89,135-137 In general, this implies ensuring excellent oxygenation, ventilation, and intubation under protection of profound sedation or ­anesthesia, with the assistance of neuromuscular blockade (Box 119-5). Neurologists and neurosurgeons are frequently loathe to relinquish the opportunity to examine the patient following intubation, but the risk of life-threatening intracranial hypertension justifies temporarily obscuring the neurologic examination. In most cases, adequate assessment is possible before intubation, and diagnostic studies require deep sedation for a period afterward. The patient is provided 100% oxygen by bag and mask. An anesthetic or sedative agent in combination with a neuromuscular blocking agent is given, and manual ventilation is initiated to lower ICP as much as possible before airway manipulation. Although extreme hyperventilation may decrease CBF to ischemic levels, current guidelines support ventilation to a Paco2 of approximately 30 to 35 mm Hg for patients with intracranial hypertension.138 In the hemodynamically stable patient, thiopental provides relatively deep anesthesia associated with a rapid decline in CMRo2, CBF, and ICP.135,137 Alternative agents include Box 119–5  Intubation for Increased Intracranial Pressure • P repare equipment • Monitor heart rate, blood pressure, and arterial oxygen saturation • Provide 100% oxygen and assisted ventilation as tolerated by patient • Consider possible difficult airway • If no airway contraindications, administer anesthetic and neuromuscular blocking agents: • Associated cardiovascular compromise or hypovolemia: • Midazolam (0.2–0.3 mg/kg IV) and fentanyl (5–10 μg/kg IV) plus lidocaine (1.0–1.5 mg/kg IV) and rocuronium (0.6–1.2 mg/kg IV) or other relaxant; consider etomidate (0.3 mg/kg IV) • No associated cardiovascular compromise or hypovolemia: • Thiopental (4–6 mg/kg IV) plus lidocaine (1.0 mg/kg IV), plus rocuronium (0.6–1.2 mg/kg IV) or other relaxant • Ventilate patient until drug effect achieved (consider shortterm hyperventilation in patients with signs of critically elevated intracranial pressure) • Perform laryngoscopy and orotracheal intubation IV, Intravenous.

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narcotic analgesics alone or in combination with a benzodiazepine, which has less hemodynamic effect but also less effect on CMRo2 unless given in anesthetic doses. Etomidate is widely used in patients with suspected intracranial hypertension. Its ability to decrease CBF without apparent detrimental effect on systemic hemodynamic stability makes it a useful agent, although concerns about its effect on adrenal function, perhaps even following a single dose, require caution in the patient with sepsis or shock. Because it lacks analgesic properties, combining it with an intravenous narcotic agent should be considered. Lidocaine, 1 to 1.5 mg/kg, decreases CMRo2 and modestly decreases the systemic and intracranial hypertensive response and the cough reflex, as long as a dose below the seizure-producing threshold is used. Effective serum concentrations are obtained more quickly and at lower doses by the intravenous route than when the agent is administered endotracheally. The available literature addresses patients fully premedicated and monitored undergoing neurosurgical procedures or patients already intubated, ventilated, and monitored in the ICU. Studies addressing intubation in the acute setting are lacking and unlikely to be accomplished.138-142 Although the classic recommendation has been to avoid ketamine in patients with elevated ICP because of its potential to further increase pressure, newer studies suggest that ketamine may be safe in this population. It does, however, increase systemic blood pressure and CBF and most likely should be avoided in patients at risk of failed autoregulation until further evidence is available.74,143-145 In addition, evidence that ketamine is associated with neuronal injury in immature animal models supports continued caution with respect to its use in patients with elevated intracranial pressure. In nearly all patients, orotracheal intubation is preferred because it is accomplished quickly and easily with less risk of prolonged manipulation and interrupted ventilation. Nasotracheal intubation is contraindicated in patients with basilar skull fractures and CSF leaks as a potential source of infection or even perforation of the cribriform plate and intracranial tube placement.

Cervical Spine Instability Flexion and extension of the head on the neck occur between the atlas (C1) and the basiocciput. Rotation occurs between the atlas and axis (C2), as the thin arch of the atlas pivots around the odontoid process. Below the axis, the cervical vertebrae articulate with each other anteriorly at the intervertebral disks and posteriorly at the facet joints. Further neck flexion and extension occur at these joints. Anterior and posterior ligaments complete the stable spine. Spinal cord injury generally occurs as a result of bony fracture, compression, or disruption of cervical ligaments. In young children, actual ligamentous disruption or bony fracture is not necessary for severe cord injury, even transection, to occur; extreme stretching, as may occur in acceleration or deceleration injury, is sufficient.146-148 Instability results from disruption of both the anterior and posterior columns. Congenital or degenerative anatomic abnormalities, penetrating wounds, or expanding mass lesions in the spinal canal may compromise cord integrity. During routine intubation, the intensivist flexes the neck and extends the head. In children with known or suspected

cervical spine injury or instability resulting from other causes (e.g., Down syndrome or rheumatoid arthritis), manipulating the head and neck for intubation risks extending the existing condition or injury and may precipitate new problems. Cervical spine films and knowledge about the nature of the traumatic event help define the precise injury and predict maneuvers most likely to do harm, but such information rarely is complete and may be falsely reassuring. The ideal approach to intubation in this setting is controversial.149-152 Although evidence in cadavers, in addition to common sense, indicates that typical airway maneuvers can cause anterior or posterior subluxation or widening of the disk space, evidence in patients is lacking.153 Axial traction increases distraction and even subluxation in some patients154; in others traction is helpful. However, information about the appropriate amount of force or the correct plane in which it should be applied is rarely sufficient to make a timely informed decision. Therefore immobilization of the head and neck in the midline without traction is recommended. Current advanced trauma life support guidelines no longer recommend blind nasotracheal intubation.155,156 Orotracheal intubation is more reliably accomplished and less time-­ consuming than blind nasotracheal intubation and is associated with far fewer complications, including tube malposition and bleeding, even in adults.157 The high anterior location of the pediatric larynx makes nasotracheal intubation even more difficult in young children. As a result, it is rarely a necessary or desirable choice for emergency airway stabilization in children. Just as manipulation of the airway for intubation may risk additional cord injury, patient movement can cause additional damage. Few children of any age will tolerate awake intubation by any route without violent struggle. Even heavily sedated patients likely will cough upon stimulation of the airway. Patients with spinal cord injuries are at risk for extreme hyperkalemia and resulting dysrhythmias or cardiac arrest following administration of succinylcholine. This response occurs from approximately 48 hours to 6 to 9 months after injury. Cervical injury often also disrupts sympathetic nervous system outflow and results in unopposed vagal tone and severe bradycardia. For these reasons, in most instances intubation is best accomplished in these patients via the orotracheal route, using an intravenous anesthetic or combination of sedative and analgesic agents, atropine, and a nondepolarizing neuromuscular blocking agent with an assistant immobilizing the head and neck in neutral position with one hand over the ear on each side of the head. If time, equipment, and available expertise permit, fiberoptic bronchoscopy may assist visualization of the larynx and intubation with minimal head or neck movement.158 If orotracheal or nasotracheal intubation cannot be accomplished because of associated facial or airway injuries or other technical obstacles, cricothyrotomy or primary tracheotomy may be indicated. However, no data support either the necessity or safety of routinely using a surgical approach before attempting orotracheal intubation.

Upper Airway Obstruction Upper airway obstruction may result from many disorders (see Chapter 39). When symptoms are related to loss of oropharyngeal muscle tone, changing the patient’s position,

Chapter 119 — Airway Management

reversing the effects of a drug, or placing a nasal airway may be sufficient, if the duration of the underlying process likely will be brief. However, when airway structures likely are severely or progressively distorted by edema, inflammation, trauma, or another space-occupying process, achieving an endotracheal airway is necessary. Patients should be allowed to assume whatever position is most comfortable. Supplemental oxygen is provided at the maximum concentration possible, but a young child’s anxiety should not be heightened with an overly aggressive approach with a mask. Contrary to popular belief, breathing can be assisted in nearly all cases by application of positive pressure, initially with continuous positive airway pressure and then gradually with assisted breaths. In general, no action should be taken that compromises the child’s ability to breathe spontaneously until the capacity to control ventilation is certain. In particular, use of neuromuscular blocking agents is dangerous and inappropriate until after the airway is controlled. Distortion of the airway may be so extreme that recognition of landmarks for intubation is impossible, and loss of pharyngeal tone in such patients may remove the last barrier to complete airway occlusion. However, reducing a child’s anxiety with cautious sedation (with a reversible agent) may decrease peak inspiratory flow rate and symptoms of obstruction and make it easier to assist breathing and establish an artificial airway. When possible the child is gently lowered to a supine position (or to 30 degrees) and intubated by the orotracheal route. When time and available expertise permit, intubation in the operating room using an inhalational anesthetic in a high oxygen concentration allows spontaneous breathing until the patient is deeply anesthetized and untroubled by airway manipulation. This method may be especially helpful in cases of supraglottitis. In most cases, the proper tube size is 0.5 to 1.0 mm smaller in diameter than predicted for age because of airway inflammation and edema, and no leak will be present. Extubation usually is well tolerated when a leak has developed.

Facial and Laryngotracheal Injury Children with facial injuries present airway problems nearly as varied as the injuries themselves. Appropriate management depends primarily on accurate assessment of airway patency at presentation, the rate of bleeding (if any) into the airway, and the amount of additional swelling and distortion likely to occur later. Evaluation of possible ocular and intracranial injury must proceed simultaneously. Profuse bleeding, unstable facial fractures, or aspiration of blood, gastric contents, or teeth causes early respiratory distress. Maxillary fractures may result in a free-floating maxilla with occlusion of the nasopharynx and pressure on the tongue. Isolated mandibular fractures often cause trismus but rarely cause airway obstruction or interfere with visualization of the larynx. Airway management begins with suctioning blood and debris from the mouth and pharynx. If permitted by other injuries, the child is placed with the head down and turned to the side. The tongue and maxilla are pulled forward manually if necessary. A spontaneously breathing patient receives oxygen by mask and may not require further intervention before surgery. Patients with persistent obstruction may require an immediate artificial airway.

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In most cases, orotracheal intubation is accomplished first. If ventilation can be assisted with bag and mask and bleeding is controlled, the patient may be sedated, paralyzed, and intubated with full stomach precautions. If bag-mask ventilation exacerbates airway obstruction, awake intubation may be necessary. Uncontrollable bleeding, inability to visualize the larynx, or violent struggle in a child with cervical spine instability or evidence of increased ICP may make a primary tracheostomy desirable. Nasotracheal and nasogastric tubes are avoided until the possibility of a basilar skull fracture and CSF leak is eliminated. Laryngotracheal injuries may be subtle or dramatic. They should be suspected in children with a history of anterior neck trauma and often cause hoarseness, stridor, subcutaneous emphysema, pneumothorax, or pneumomediastinum. Aerosolized epinephrine may temporarily decrease swelling and provide a little extra time to evaluate the airway and plan intervention. Awake intubation with cautious sedation and topical anesthesia that is conducted under direct vision by laryngoscopy or fiberoptic bronchoscopy minimizes the risk of sudden, complete obstruction or creation of a false passage adjacent to the airway.

Open Globe Injury Children with penetrating eye injuries may require emergency intubation for respiratory failure resulting from associated injuries or other underlying problems. Management in these cases seeks to prevent increased intraocular pressure with subsequent extrusion of the vitreous and permanent blindness. Intraocular pressure can be increased by struggling, crying, coughing, straining, or rubbing the eye. Hypoxia and hypercarbia can increase intraocular pressure. In general, central nervous system depressants lower intraocular pressure, with the possible exception of ketamine. Intubation should be performed smoothly under full muscle relaxation if possible, taking into consideration associated injuries and the risk of a full stomach. The child should be preoxygenated with 100% oxygen, taking care not to apply pressure to the eye with the mask. Efforts to empty the stomach are delayed until the patient is fully relaxed and intubated. In hemodynamically stable patients, thiopental or other rapidly acting sedatives/anesthetics are administered, followed by a nondepolarizing neuromuscular blocking agent if other airway anatomy permits. Succinylcholine, a depolarizing relaxant, has been associated with increased intraocular pressure, even in the absence of fasciculations. As in patients with head trauma, a combination of sedative and analgesic agents may replace thiopental if hemodynamic stability is uncertain. Lidocaine supplements the effect of other agents in blunting the rise in intraocular pressure that may occur even during a smooth intubation. Heavy sedation or paralysis should be maintained following intubation until after repair.

Alternative Approaches to the Airway

Lighted Intubation Stylet (Light Wand)– Assisted Intubation A number of lighted intubation stylets have become available in the past decade. Each uses transillumination of the neck to guide placement of an endotracheal tube. The devices consist

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Section VII — Environmental Hazards, Trauma, Pharmacology, and Anesthesia

of a handle containing the power source and a malleable wand (stylet) with a light at the tip. Pediatric versions accommodate tubes as small as 3.5 mm. Use of the lighted stylet for intubation is a technique recommended for use in patients with airways that are difficult to manage. Reported experience in children is limited, but the technique has been successful in the hands of both highly skilled and novice operators.159-163 The equipment is fairly simple to use and easy to learn. It does not require visualization of the airway, is less stimulating than laryngoscopy, allows nasal or oral intubation, and is portable and relatively inexpensive. Reported series indicate that mucosal and dental injuries are uncommon, and sore throat is less of a problem than following standard laryngoscopy.164 Because intubation may be accomplished from the patient’s side, it may be useful in awkward settings such as emergency transport vehicles. Potential disadvantages include trauma to the upper airway and larynx. Anything that obscures transmission of light through the anterior neck interferes with its use, including scarring, massive edema, subcutaneous emphysema, or mass lesions. Profuse bleeding or thick airway secretions that obscure the bulb also interfere with effective use. A lubricated lighted stylet is inserted through an endotracheal tube of desired size until the light is just short of the end of the tube, and the tube is firmly attached. The tube and stylet are bent to approximately 90 degrees, just proximal to the cuff if present. Dimming the room lights improves appreciation of the transillumination. The intubator may stand at the head of the bed or to the side of the patient. The head is extended. A shoulder roll may be useful. The mandible and tongue are pulled forward and upward by the intubator, and the styletted tube is introduced into the patient’s mouth in the midline. It is advanced into the pharynx, while the operator observes transillumination of the soft tissues of the neck. Entry into the airway typically is recognized by the presence of a focused glow of light in the midline below the thyroid prominence; more diffuse light suggests esophageal placement. The tube is advanced until the light is at the level of the sternal notch. The lighted stylet is withdrawn and placement is confirmed with capnography. Nasal intubation is possible with the light wand. In this case, the trocar is removed to increase the flexibility of the device. When a glow is noted above the thyroid prominence, the tube is likely in the vallecula. The epiglottis can be moved out of the way with a jaw thrust, allowing further advancement of the tube into the trachea. An alternative is to flex the patient’s neck, as is sometimes necessary with visualized nasotracheal intubation.

Laryngeal Mask Airway The laryngeal mask airway (LMA) is a relatively new and fairly safe means of securing a difficult to manage airway in an infant or child.165-167 It was designed to provide a supraglottic airway device that would offer the benefit of noninvasive ventilation. Its use rapidly gained acceptance in anesthesiology and has been incorporated into the American Academy of Anesthesiology difficult airway algorithm.46 It consists of a small mask with an inflatable rim and a tube with a “universal adaptor,” which permits attachment to a resuscitation or anesthesia bag or ventilator (Figure 119-11). The original

A

B Figure 119–11.  LMA. A, Mask portion of the airway with the rim deflated for insertion (left) and inflated (right). B, LMA in position, with the rim inflated around the laryngeal inlet. (From Efrat R, Kadari A, Katz S: The laryngeal mask airway in pediatric anesthesia: experience with 120 patients undergoing elective groin surgery, J Pediatr Surg 29:206, 1994.)

LMA consists of a wide-bore tube designed to sit in the hypopharynx and is attached to an inflatable bowl-shaped base that bypasses the tongue, sits around the epiglottis, conforms to the shape of the larynx, and provides a low-pressure seal around the supraglottic area.168 The LMA is available in a wide range of sizes, allowing use in very small infants to very large adolescents and adults. Choice of LMA size is based on weight: size 1 for patients weighing 2.5 to 6.0 kg, size 2 for patients weighing 6.0 to 30 kg, and size 3 for patients weighing more than 30 kg.169,170 Since the initial development of the LMA, several other types have been designed, including the flexible LMA, intubating LMA, disposable LMA, and ProSeal LMA, not all of which are available in pediatric sizes.171

Chapter 119 — Airway Management

The insertion technique can be learned quickly by physicians and other providers, including emergency transport personnel, often more quickly than endotracheal intubation. Experience with a mannequin appears to be effective training. Once in place, the LMA can serve as a means of ventilating the patient until the desired definitive airway can be established. It can facilitate subsequent tracheal intubation, if desired, either with blind technique or via fiberoptic bronchoscopy. Insertion of the LMA does not require muscle relaxation or the use of a laryngoscope and is therefore considered a “blind” technique. Topical anesthesia, with lidocaine spray or lidocaine jelly applied to the inflatable rim, is helpful in patients with intact protective airway reflexes who are awake. With the rim deflated or partially inflated, the LMA is advanced along the posterior pharyngeal wall with the dorsum of the mask facing the palate until resistance of the upper esophageal sphincter is encountered. The cuff is then inflated, forming a seal around the laryngeal outlet, and the attached tube is connected to a source of oxygen and positive pressure (Figure 119-12). Proper placement is essential but is most uncertain in infants requiring the LMA size 1, most likely because the margin of error for placement in the small pharynx is so small. In general, the risk of downfolding the epiglottis, thus occluding the trachea, is greater in children than in adults. Successful placement depends on the shape and tone of the pharynx,

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adequate matching of the cuff, the palatopharyngeal curve and shape of the posterior pharynx, the extent to which anterior structures (such as tonsils) obliterate the curve, the position of the head and neck, efficacy of digital manipulation, and the depth of anesthesia/sedation, muscle relaxation, or loss of airway reflexes.166 Tissue trauma is uncommon, and the need to manipulate the cervical spine during placement is minimal. In most patients the autonomic response to placement is less pronounced than with laryngoscopy and intubation. On the other hand, the device does not fully protect against aspiration in the setting of a full stomach. In addition, it may not be effective in patients with glottic or subglottic pathology. Although its primary use is in the operating room, growing experience demonstrates that the LMA can be lifesaving in a variety of other settings when no other nonsurgical means of maintaining an airway is successful, particularly in patients with anatomically abnormal airways.172 Success with airway management in the operating room with children with airways that are anticipated to be difficult to manage, including patients with Pierre Robin, Treacher Collins, and Goldenare syndromes, suggests that the LMA would be valuable for managing such patients in emergency settings such as the emergency department or ICU. The ease and rapidity of insertion and decreased gastric air insufflation during resuscitation make it a valuable tool when intubation fails during adult resuscitation.173 The current Pediatric Advanced Life Support

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Figure 119–12.  Inserting the LMA. Preoxygenate the patient as necessary. 1, Deflate the cuff against a flat surface with index finger and middle finger on either side of the bowl. 2, Hold the LMA like a pen, with the index finger at the junction of the tube and mask. 3 and 4, Insert the LMA into the mouth and advance, following the palate and posterior pharyngeal wall until resistance is met. 5, Let go of the mask and tube. 6, Inflate the cuff, allowing the device to move into correct position. (Modified from Ambulance technician study, http://www.ambulancetechnicianstudy.co.uk/.)

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Section VII — Environmental Hazards, Trauma, Pharmacology, and Anesthesia

textbook supports the LMA as an effective alternative to intubation during resuscitation when inserted by trained providers.174 In neonatal resuscitation, when face mask ventilation or intubation is not successful, the LMA provides a means of rapidly improving oxygenation and heart rate. It is not, however, effective for aspirating meconium and may be inadequate for infants with severely noncompliant lungs. Use by prehospital personnel has been effective for critically ill adults, but experience in children in the field has not been reported.175,176 The LMA is poorly tolerated by patients with intact protective reflexes, so its use is largely limited to those with severely depressed levels of consciousness or heavy sedation or anesthesia. Lidocaine jelly on the inflatable rim or lidocaine pharyngeal spray may promote tolerance in patients with active airway reflexes. A disadvantage with use of the LMA is the inability to use airway pressures greater than approximately 20 mm Hg to prevent air leaking around the mask and to avoid gastric distention, and therefore it is not an optimal airway device in patients with severe subglottic airway obstruction, parenchymal disease requiring high ventilatory pressures, or in obese persons.177 It also is not the ideal technique to use in a patient with a full stomach because its design does not prohibit aspiration of gastric contents. However, in an emergency situation the benefit of providing oxygenation and ventilation via an LMA outweighs the risk of an aspiration event. Other scenarios that may limit placement of the LMA include excessive neck extension, limited mouth opening, or excessive application of cricoid pressure.177 Although the seal is somewhat protective, patients with a full stomach remain at risk for aspiration. Positive airway pressure should be minimized as much as possible and a nasogastric tube passed to decrease gastric distension. Cricoid pressure may further decrease the risk of aspiration but also may interfere with proper LMA placement. If desired, an endotracheal tube can be inserted through the mask, either blindly or with fiberoptic bronchoscopy.178

Tracheostomy Indications for tracheostomy include structural abnormalities of the upper airway requiring surgery, laryngeal trauma or complex craniofacial injury, severe facial burns, congenital anomalies lacking surgical treatment, vocal cord paralysis, and iatrogenic injury to the upper airway. Severe chronic neurologic dysfunction with impaired protective reflexes is an additional indication. Even in the absence of evidence of upper airway damage, tracheostomy may be performed to provide a more comfortable airway, which simultaneously allows airway protection, respiratory support, and greater patient mobility so that nutritional, developmental, and psychosocial needs may be met, especially, but not only, in patients undergoing chronic ventilation.179-182 Tracheostomy spares laryngeal and subglottic structures from the trauma of an artificial airway, particularly in active or thrashing patients. Tracheostomy tubes are less likely to be inadvertently dislodged or to become obstructed, but if either problem occurs early following tracheostomy, it is more likely to be catastrophic. Because the tube is inserted below the cricoid ring, it often is possible to use a larger tracheostomy tube than endotracheal tube. Nevertheless, a larger leak around the tube may interfere markedly with effective ventilation in patients requiring high airway pressures.

Complications in the early postoperative period include bleeding, subcutaneous air dissection, pneumothorax, pneumomediastinum, injury to the recurrent laryngeal nerve, and death, usually as a consequence of loss of control of the airway intraoperatively or an unrecognized complication from the preceding list. Nearly all pediatric patients can and should be intubated before tracheostomy. Prior intubation decreases the incidence of most technical problems. Exceptions include patients with complex facial or airway injuries or deformities and those in whom no other means of establishing an airway have been successful. Wound colonization occurs rapidly. Bacterial infection may occur, rarely involving major cervical and mediastinal structures. Swallowing difficulty is common and may result from the tube and fixation tapes limiting excursion of the larynx. Aspiration may result from alteration of the laryngeal closure reflex. Tracheostomy tube obstruction or accidental dislodgment is suspected when the patient becomes agitated and shows signs of increased respiratory distress, a suction catheter no longer passes freely, manual ventilation is ineffective, or, in case of dislodgment, the child is suddenly able to vocalize. In such cases the tube should be removed and replaced with a new one. The child is placed supine with the head and neck extended. Oxygen is delivered to the nose, mouth, and tracheal stoma. If manual ventilation is necessary, the stoma can be occluded to allow bag-mask ventilation as previously described. A fresh tracheostomy tube is inserted, initially directly posteriorly and then caudad. Replacement with a smaller tube or endotracheal tube may be necessary if resistance is encountered. Resistance to passage of a suction catheter or ineffective ventilation following replacement of a tracheostomy tube, particularly in the first 7 to 10 days postoperatively, is highly suggestive of creation of a “false passage” in a tissue plane outside the tracheal lumen. Reestablishing tracheal cannulation may require surgical intervention. Life-threatening pneumothorax or pneumomediastinum occurs frequently in such patients. Late complications include granuloma or stricture formation at the stoma or where the tip of the tube meets the tracheal wall. Persistent posterior wall pressure may cause tracheoesophageal fistula formation. Erosion into the innominate artery is another rare occurrence, usually when the tracheostomy incision is below the third tracheal ring. The importance of an experienced, well-trained staff immediately available to address problems is supported by data demonstrating that mortality related to tracheostomy is significantly lower when performed in a children’s hospital and decreases with increasing volume.183 Decannulation occurs when the indications for tracheostomy are no longer present. Diagnostic laryngotracheobronchoscopy before a planned decannulation permits identification of problems likely to interfere with effective breathing, including granulation tissue, severely stenotic areas, or vocal cord abnormalities. If none is present, the indwelling tube is replaced with successively smaller tubes until the smallest available is in place and the child is breathing well. If no distress occurs, the tube is removed and the stoma is covered.

Cricothyrotomy and Retrograde Intubation Although airway management by endotracheal intubation is possible and endotracheal intubation is the appropriate first choice in the vast majority of pediatric patients, intubation is

Chapter 119 — Airway Management

not possible or should not be done on certain occasions. Such situations include massive facial trauma, oropharyngeal hemorrhage or presence of a foreign body, or severe upper airway obstruction.184 Cricothyrotomy is an alternative to tracheostomy for rapidly establishing an airway in apneic or severely distressed patients. The child’s head and neck are extended with a roll under the shoulders. The cricothyroid membrane is palpated between the inferior margin of the thyroid cartilage and the superior edge of the cricoid cartilage. With one hand (or an assistant) stabilizing the larynx and trachea, the membrane is punctured in the midline with a large angiocatheter, the stylet is withdrawn, and the catheter is connected to a source of oxygen using the connector to a size 3 endotracheal tube. Kits are available that facilitate cricothyrotomy using the Seldinger technique. Oxygenation is rapidly improved in spontaneously breathing patients, but carbon dioxide elimination is minimal. Transtracheal jet ventilation is effective through such catheters, provided that the upper airway permits passive exhalation; otherwise, severe hyperinflation and life-threatening barotrauma are certain. Retrograde intubation can be accomplished by this approach. Once the cricothyroid membrane has been punctured and the catheter has been placed in the tracheal lumen,

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a long wire from a vascular access kit is advanced cephalad into the mouth. With the wire firmly secure, an ETT may be advanced into the trachea. Once the tube is in the tracheal lumen, the wire is withdrawn and the tube is further advanced into the desired position. If the wire is insufficiently stiff to permit passage of the tube into the trachea, an ETT exchanger can be advanced over the wire first, followed by the ETT. In adults and adolescents, a small horizontal incision over the cricothyroid membrane is an alternative approach. Once the membrane is incised, it is spread vertically, and a standard tracheostomy or ETT is inserted into the tracheal lumen. This approach is not recommended in infants and young children except in highly skilled hands because of the potential for grave injury to a small, soft trachea or nearby neurovascular structures. Complications are similar to those of tracheostomy. Complication rates of 10% to 40% are reported in adults.184 Few experiences have been reported in pediatric patients, particularly in younger children. References are available online at http://www.expertconsult. com.