The Difficult Airway in Pediatrics

Advances in Anesthesia 31 (2013) 31–60

ADVANCES IN ANESTHESIA The Difficult Airway in Pediatrics Jason Bryant, MDa,b, Senthil G. Krishna, MDa,b, Joseph D. Tobias, MDa,c,* a

Department of Anesthesiology & Pain Medicine, Nationwide Children’s Hospital, Columbus, Ohio 43205, USA; bDepartment of Anesthesiology & Pain Medicine, The Ohio State University, Columbus, Ohio, USA; cDepartments of Anesthesiology, Pain Medicine and Pediatrics, The Ohio State University, Columbus, Ohio, USA

Keywords 

Airway  Management  Anesthetic  Children

Key points 

Airway management remains the key component of resuscitative efforts in emergency situations. Resuscitative efforts will be futile unless oxygenation and ventilation can be provided or re-established quickly.



Although problematic management of the pediatric airway including difficulties with mask ventilation or unsuccessful endotracheal intubation remains rare, it is one of the primary causes of perioperative morbidity and mortality.



The airway examination and evaluation remains an integral component of the preoperative assessment with the goal of identifying potential airway issues.



The primary tools to deal with a ‘‘cannot intubate-cannot ventilate’’ scenario in the pediatric population include a supraglottic airway, indirect laryngoscope and a lighted stylet. When these tools fail, emergent cricothyrotomy may be necessary.

INTRODUCTION Airway management is a key component in various clinical scenarios, including the operating room during the provision of anesthetic care, in the pediatric intensive care unit (ICU), the emergency department, and during resuscitative efforts. In emergency situations, resuscitative efforts are futile unless oxygenation and ventilation can be provided or reestablished quickly. Given these concerns, there remains intense focus on airway management in various clinical scenarios as well as alternative means to provide such care when routine

*Corresponding author. E-mail address: [email protected] 0737-6146/13/$ – see front matter http://dx.doi.org/10.1016/j.aan.2013.08.003

Ó 2013 Elsevier Inc. All rights reserved.

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practices such as bag-valve-mask ventilation or direct laryngoscopy and endotracheal intubation fail. Although, in most circumstances, the management of the pediatric airway proceeds uneventfully, in specific circumstances, significant morbidity or even mortality may result from adverse events occurring during the management of the routine, urgent, and emergent airway in infants and children. Problematic management of the pediatric airway, defined as difficulties with mask ventilation or when endotracheal intubation is unsuccessful, is rare. Poor visualization of the glottis or laryngeal inlet during direct laryngoscopy, defined as a Cormack and Lehane view greater than or equal to grade 3 (Table 1) varied between approximately 1 in 100 to 1 in 200 cases [1,2]. The incidence may be slightly higher in patients undergoing cardiac surgery, but many of these patients were noted to be associated with specific syndromes, which in itself is a known isolated risk factor [3,4]. The incidence of such problems may be magnified when airway management is performed outside of the operating room setting in either the ICU or the emergency department [5–7]. Despite these data and the supposition that airway difficulties may not occur with experienced clinicians, the literature continues to show the potential impact of such problems. The Perioperative Cardiac Arrest (POCA) registry shows that respiratory adverse events remain the second most common cause for perioperative cardiac arrest in children following hemodynamic compromise related to blood loss during major surgical procedures [8]. Although the incidence of perioperative complications related to airway management in infants and children has declined, these issues remain a primary cause of perioperative morbidity [9]. A closed claims analysis from 1973 to 2000 showed a decrease in the proportion of claims related to inadequate oxygenation and ventilation in the pediatric population; however, claims for death or brain damage still accounted for most of the cases [9]. This article reviews an assessment algorithm for the pediatric airway, potential causes of difficulties with oxygenation and ventilation, medications used for airway management, equipment and airway adjuncts, an approach to the cannot intubate–cannot ventilate (CICV) scenario, and suggestions for development of a difficult airway cart. THE AIRWAY ASSESSMENT IN INFANTS AND CHILDREN The airway examination and evaluation remains an integral component of the physical examination performed during the preoperative assessment. Its goal is to identify those patients in whom airway management may be problematic. Table 1 Cormack and Lehane scale Grade Grade Grade Grade

1 2 3 4

Full view of glottis Only posterior commissure is visible Only the tip of epiglottis is visible No glottis structure is visible

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However, no single screening test or even compilation of tests maintains the needed sensitivity and specificity to be universally applicable. Various formulas and screening tests have been suggested for the adult population; however, these are not all readily transferable to the pediatric patient. In the retrospective study by Heinrich and colleagues [1], which involved a 5-year period and 11,219 general anesthesia procedures in pediatric patients, the overall incidence of difficult laryngoscopy (defined as a Cormack and Lehane grade III or IV view) was 1.35%. Risk factors included age less than 1 year (4.7% vs 0.7%), American Society of Anesthesiologists (ASA) physical status III and IV, a high Mallampati score (III and IV) (Table 2), a low body mass index (BMI), and patients undergoing oromaxillofacial surgery or cardiac surgery. The same investigators reviewed the anesthetic care of 102,306 adult cases and reported that the overall rate of difficult laryngoscopy was 4.9%, again defining this as a Cormack and Lehane grade III or IV view [10]. Risk factors included male gender, Mallampati score III and IV, obesity with a BMI greater than or equal to 35 kg/m2, and ASA physical status III or IV. Again, they noted that specific surgical procedures were also identifying factors, with a higher incidence of difficulty laryngoscopy noted in patients undergoing oromaxillofacial, ear nose throat (ENT) surgery, and cardiac surgery. A key statement from the ASA emphasizes that the evaluation of the airway ‘‘should be conducted, whenever feasible, prior to the initiation of anesthetic care and airway management in all patients[8].’’ Even in the emergency setting, time must be made for at least a cursory examination of the airway and an assessment of the feasibility of the endotracheal intubation. The intent of this examination is to detect physical characteristics that may indicate the presence of a difficult airway. Although a high percentage of difficulties with airway management are encountered in patients with specific clinical syndromes, issues can arise with the apparently normal child with no previous medical history. The use of specific physical assessment tools allows clinicians to classify the airway and potentially identify it as either the normal airway and/or the anticipated difficult airway. By doing so, clinicians then embark on the best process to expeditiously secure the airway. However, as noted by the clinical practice of pediatric anesthesia, the greatest risk of morbidity is in the unanticipated difficult airway (discussed later). During the airway

Table 2 The Mallampati scoring system Class

Anatomic features visualized

Class 1 Class 2

Complete visualization of the soft palate, uvula, and tonsilar pillars Complete visualization of the soft palate with partial visualization of the uvula and tonsilar pillars Visualization of only the base of the uvula and the soft palate. No visualization of the distal uvula or tonsilar pillars No visualization of the soft palate, uvula, or tonsilar pillars

Class 3 Class 4

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examination, the anesthesia provider should attempt to answer the questions noted in Box 1. In addition to the features outlined earlier, specific phenotypic features have been shown to be associated with difficulties with airway management. Many of these impede the alignment of the structures required for endotracheal intubation including the oral, pharyngeal, and glottic openings (Table 3). As noted earlier, various congenital anomalies and genetic syndromes have been reported to result in difficulties with airway management. These conditions are reviewed by Butler and colleagues [4]. An additional physical feature that may alert the anesthesia provider to the potential for a difficult airway is abnormalities of the external ear [11]. The study cohort included 93 patients with microtia presenting for surgical reconstruction. Twelve had bilateral microtia and the remaining 81 had unilateral anomalies. An age-matched control group was similar to the study subjects in weight, height, and gender. The incidence of difficulty in laryngeal visualization (defined as a Cormack and Lehane grade III or IV view) was 5 of 12 (42%) in the patients with bilateral microtia, 2 of 81 (2%) with unilateral microtia, and 0 of 93 in the control group. More recently in the adult population, it has been suggested that a clinical diagnosis of obstructive sleep apnea is associated with a higher incidence of difficult intubation [12]. In many patients, this relates not only to the weight or BMI but also correlates with the neck circumference. In a study of 123 obese adults, Kim and colleagues [13] noted that difficult laryngoscopy correlated with the ratio of the neck circumference (NC) to the thyromental distance (TM). Of the various relationships that they investigated, the NC/TM ratio had the highest sensitivity, a negative predictive value, and the largest area under the curve on a receiver operator curve [13]. One other scoring system that merits mention, given its frequent use and validity in the adult population, is the Wilson Risk Score (Table 4) [14]. A total of 3 or more of these physical features predicted 75% of difficult laryngoscopies, whereas 4 or more predicted 90%. Given that no specific test or feature has been shown to be 100% successful, there is a current trend toward combining the various scoring systems or physical features in an attempt to improve the specificity and sensitivity of these systems, especially in the pediatric patient [15].

Box 1: Airway evaluation questions 1. Will I be able to maintain ventilation with a bag-valve-mask device? 2. Will an oral or nasal airway be helpful to improve bag-valve-mask ventilation? 3. Can a supraglottic device be placed if bag-valve-mask ventilation is difficult? 4. Is there going to be a problem with direct laryngoscopy and placement of an endotracheal tube into the trachea? 5. Is there adequate access to the neck and trachea for placement of a surgical airway if needed?

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Table 3 Physical features that suggest a difficult airway Physical feature

Clinical finding

Length of upper incisors Relation of maxillary and mandibular incisors during normal closure Relation of maxillary and mandibular incisors during voluntary protrusion of mandible Interincisor distance

Long Overbite with maxillary incisors anterior to mandibular incisors

Visibility of uvula Shape of the palate Size and/or integrity of the submandibular space Thyromental distance Length of neck Neck circumference Range of motion of head and neck a

Cannot bring mandibular incisors in front of maxillary incisors Less than 3 cm (adult) or less than 2 finger breadthsa Mallampati grade 3 or 4 Highly arched or narrow Small and/or indurated, firm, or mass present Less than 3 cm (adult) or less than 3 finger breadthsa Short Large neck circumference Limited flexion and extension

For this evaluation in a child, the patient’s own fingers should be used.

CAUSES OF DIFFICULTIES WITH OXYGENATION AND VENTILATION In general, problems with oxygenation and ventilation may result from: 1. 2. 3. 4. 5.

Poor or improper mask fit and difficulties with bag-valve-mask ventilation Difficulties with visualization during direct laryngoscopy Problems with placement of a supraglottic device Problems with placement of an endotracheal tube Airway and pulmonary parenchymal problems distal to the endotracheal tube

Table 4 Wilson risk score for difficult endotracheal intubation Risk factor

0

1

2

Weight (kg) Head and neck movement Jaw movement (cm)

Less than 90 Greater than 90

Between 90–110 Approximately 90

Greater than 110 Less than 90

Incisor gap greater than 5 and subluxation greater than 0 Normal Normal

Incisor gap less than 5 and subluxation greater than 0

Incisor gap less than 5 and subluxation less than 0

Moderate Moderate

Severe Severe

Receding mandible Buck teeth

Score of 3 or more predicts 75% incidence of difficult endotracheal intubations, whereas 4 or more predicts 90%.

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Poor mask fit and difficulties with bag-valve-mask ventilation Difficulties with mask fit and bag-valve-mask ventilation may be caused by true anatomic abnormalities (craniofacial malformations, oropharyngeal or laryngeal tumors) or functional abnormalities (genioglossus relaxation with tongue obstruction, tonsilar hypertrophy, laryngospasm) at multiple levels and times during induction of the pediatric patient. Anatomic abnormalities that may make mask fit difficult (midface hypoplasia) are generally noted during the preoperative assessment. Masks with inflated cuffs (rims) may increase dead space, but provide an easy seal if the correct size and shape are chosen. Likewise, anatomic abnormalities of the larynx and trachea or external compression of such structures by masses or other lesions are generally manifested clinically before the conduct of anesthesia. Examples of such issues include laryngeal papillomas, infectious croup, epiglottis, hemangiomas, vascular rings, and mediastinal masses. During the inhalational induction of anesthesia, there is a progressive decrease in muscle tone with loss of the normal function of the genioglossus muscle and the musculature of the oropharynx. During this time, the tongue may fall into the posterior pharynx, leading to upper airway obstruction. Reestablishment of a patent airway is generally feasible by maintaining a tight mask fit with an open mouth and maneuvers to keep the tongue off the roof of the mouth (jaw thrust, neck extension). Anatomic abnormalities of the tongue or oropharynx (macroglossia or tonsilar hypertrophy) may make mask ventilation difficult following the induction of general anesthesia, although these are generally corrected by repositioning or placement of an oral or nasal airway. An oral airway that is too large or that is placed during a light plane of anesthesia can stimulate cough, emesis, and laryngospasm. In contrast, an oral airway that is too small can push the tongue posteriorly, leading to worsened obstruction. The most common cause of unexpected loss of gas exchange and hypoxemia during anesthetic induction is laryngospasm. Laryngospasm is primarily a primitive protective reflex in which stimulation of the airway with fluid or secretions results in glottic closure, thereby preventing aspiration [16]. Precipitating factors include a light plane of anesthesia, airway secretions, stimulation of the airway by an artificial airway, and tracheal extubation at an inappropriate depth of anesthesia. This problem is particularly common in children who have recently had a respiratory tract infection, which increases airway irritability, or in patients exposed to passive smoke [17,18]. Changes in the degree of airway irritability may persist for up to 4 to 6 weeks after a respiratory tract infection and make these children more susceptible than normal to episodes of laryngospasm and bronchospasm [18,19]. The clinical signs are the same as for other causes of airway obstruction, including diminished or absent gas change with paradoxic movement of the chest and abdomen. Interventions include airway maneuvers to maintain a clear airway and the application of continuous positive airway pressure (CPAP) with the administration of 100% oxygen [20,21]. It may be appropriate to deepen the level of anesthesia by the administration of propofol, which tends to relax the vocal cords and relieve laryngospasm [22,23]. Various

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suggestions have been reported in the literature regarding the dosing of propofol in the treatment of laryngospasm. Afshan and colleagues [22] administered 0.8 to 1 mg/kg to successfully treat laryngospasm in 10 of 13 patients, whereas Batra and colleagues [23] used subhypnotic doses (0.5 mg/kg). The authors recommend the use of a full anesthetic dose (2 mg/kg) of propofol. Severe episodes of laryngospasm may result in total airway obstruction with profound hypoxemia leading to bradycardia and even asystole without effective treatment. Options for the management of severe episodes include maintaining a clear airway while administering 100% oxygen with CPAP and avoidance of further instrumentation of the airway while waiting for the vocal cords to relax. Attempts to provide intermittent positive-pressure ventilation with a face mask in this scenario often distend the stomach rather than the lungs, thereby impairing subsequent ventilation or predisposing to vomiting. If the application of CPAP fails to relieve the severe obstruction and the reestablishment of gas exchange, immediate intervention is necessary with the administration of a neuromuscular blocking agent. Prolonged attempts at nonpharmacologic management are not recommended because these may result in failure to timely treat the problem, thereby resulting in hypoxemia leading to bradycardia and asystole. When laryngospasm occurs during anesthetic induction in infants and children, intravenous access may not be available. In such cases, if there are no contraindications to its use, intramuscular (IM) succinylcholine (4– 5 mg/kg) should be administered. In clinical practice, atropine is usually administered intramuscularly along with succinylcholine, although the risk of bradycardia precipitated by succinylcholine seems to be less with IM compared with IV administration [24]. The onset times of succinylcholine are more rapid with administration into the deltoid muscle rather than the quadriceps muscle, whereas some investigators have recommended administration into the tongue or submental space given its vascularity [25,26]. The submental space may be considered if profound bradycardia has already occurred because this impairs cardiac output, blood flow to major muscle groups, and hence the uptake of the IM succinylcholine. As an alternative, when profound bradycardia has occurred and the administration of succinylcholine and vasoactive medications is needed, the intraosseous (IO) route should also be considered [27,28]. Although the onset of IM succinylcholine is rapid, the onset times of IO administration for succinylcholine and other medications parallels that of intravenous administration [28]. Early IO placement may be indicated when succinylcholine is contraindicated and there is profound laryngospasm that fails to respond to airway maneuvers. The IM administration of nondepolarizing neuromuscular blocking agents is not effective in the treatment of laryngospasm given the prolonged time for uptake and the onset of neuromuscular blockade [29]. If laryngospasm occurs when intravenous access is present, succinylcholine and atropine may be administered intravenously, provided that there are no contraindications to succinylcholine. In this scenario, small doses of succinylcholine (0.1–0.2 mg/kg) are generally effective, but provide only a brief period of neuromuscular blockade. The use of small doses is necessary when

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laryngospasm occurs following the administration of cholinesterase inhibitors for the reversal of neuromuscular blockade. Because these agents also inhibit pseudocholinesterase, this may result in a prolonged duration of action of succinylcholine, especially when doses of 1 to 2 mg/kg are administered. The high likelihood that laryngospasm is the primary cause of difficulties with bag-valve-mask ventilation coupled with the low incidence of a cannot-ventilate scenario in the pediatric population has led to the idea of the cannot ventilate– then paralyze paradigm [30]. Most algorithms of the cannot ventilate–cannot intubate scenario recommend awakening the patient. However, this may not be an option in children because the hypoxemia often rapidly leads to bradycardia. Bradycardia decreases cardiac output more severely in a child than in an adult. The hypoxemic and bradycardic child does not awaken with simply discontinuing the anesthetic. Because the cannot-ventilate scenario in pediatric anesthesia has a high incidence of functional obstruction, a new treatment algorithm has been suggested of first deepening the anesthetic, then paralyzing, and then administering epinephrine, or epinephrinizing, as described by the investigators [30]. This algorithm treats the causes of functional airway obstruction as well as the developing bradycardia. Difficulties with visualization during direct laryngoscopy As with difficulties with mask ventilation, most of the problems that can lead to difficulties with visualization during direct laryngoscopy should be identified during the preoperative evaluation. The clinical assessment of the airway and physical features that may predict difficulties with laryngeal visualization during laryngoscopy are discussed earlier. In most cases, direct laryngoscopy with a standard laryngoscope blade is straightforward in children and infants. Although there is room for user preference, the traditional blade for endotracheal intubation in infants and children is the straight blade. The large tongue and the shape of the epiglottis may make it necessary to manually shift the tongue laterally and lift the epiglottis anteriorly for an optimal view for endotracheal intubation. If a curved blade is used, the flange can be used to control the tongue and the tip placed in the vallecula. Force is applied at a 45 angle, which indirectly displaces the epiglottis by the pressure at the base of the tongue. This method works well in older pediatric patients and adults. In infants and small children this technique often leaves the epiglottis obstructing the pathway for endotracheal intubation without a direct view of the vocal cords. A straight blade overcomes this by directly manipulating the epiglottis, but care must be taken to sweep the tongue because there is no flange to hold it in place. Causes of difficulty with direct laryngoscopy may be related to factors that impede the alignment of the structures required for endotracheal intubation or anatomic issues (tumors) that obscure the view. In order to successfully complete endotracheal intubation, there must be an unobstructed view from the eye of the person performing the intubation to the laryngeal inlet. Poor visualization of the laryngeal inlet may result from anatomic problems that restrict the alignment of the structures including the oral, pharyngeal, and laryngeal axis, or obstruction

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of the direct line of vision by anatomic abnormalities (tumors) or normal structures (tongue). The most common cause of this relates to the normal anatomic differences of the neonate or infant. Unlike the adult patient, the infant’s larynx is more cephalad in the neck (C3-4) compared with an adult (C4-5). The hyoid bone of the neonate is at the C2-3 level and therefore the distances between the tongue, hyoid bone, epiglottis, and the roof of the mouth are less. The proximity of the tongue to the more cephalad larynx makes visualization of the glottic inlet more difficult because it produces a more acute angle between the plane of the tongue and the plane of the glottic opening. These normal anatomic alignments may be further complicated by associated problems such as micrognathia or macroglossia. Problems that restrict the alignment of the oral, pharyngeal, and glottis structures include restriction of neck movement (flexion and extension) and limited mouth opening. In many cases, these problems can be alleviated by positioning the head in the optimal sniffing positioning for endotracheal intubation, use of a straight laryngoscope blade, and appropriately lifting the tongue anteriorly without undue pressure at the base of the epiglottis. In difficult situations, cricoid pressure may be applied to displace the glottic opening posteriorly, thereby bringing it into view. Problems with placement of a supraglottic airway Although less commonly encountered than problems with visualization of the glottic opening, anatomic issues (congenital or acquired) may also interfere with effective placement of a supraglottic airway. These devices may be chosen as the primary tool for airway management or as a rescue device when endotracheal intubation fails in the difficult airway scenario. Anatomic problems of the airway and surrounding structures encountered in both acquired and congenital abnormalities may interfere with effective placement of such devices. Placement issues may also relate to the inability to open the mouth or limitations of head flexion and extension. When placement is problematic, success may be obtained with alternative techniques such as rotation of the device during and/or after placement or placement with the cuff partially or fully deflated. Over the past 10 years, there has been an expansion of the availability of supraglottic devices. In addition, with multiple manufacturers, there are now several versions and modifications of the most commonly used supraglottic device, the laryngeal mask airway (LMA). In most clinical scenarios, the most important feature is the anesthesia provider’s experience with the specific device rather than the modification or type of device. Problems with placement of an endotracheal tube On rare occasions, adequate visualization of the glottis is obtained, but an endotracheal tube cannot be passed. These issues generally result from anatomic issues distal to the vocal cords. Other issues related to placement of the endotracheal tube include correct placement in the midportion of the trachea. Because the distance in an infant’s trachea to carina is smaller than in an adult, the endotracheal tube position must be must be confirmed not only by noting the distance at the alveolar ridge/teeth but also by ensuring bilateral breath sounds. Full-term

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newborns often need a depth of 9 cm at the alveolar ridge. After that, a commonly used rule is that the depth of insertion should equal 3 times the internal diameter (ID) of the endotracheal tube, so that a 5.0-mm endotracheal tube should be placed at 15 cm. The right lung should be auscultated first because this is the most likely lung to be ventilated if the main stem bronchus is intubated to give a baseline comparison for the left as breath sounds may be transmitted. In all circumstances, successful endotracheal intubation is documented by the presence of end-tidal carbon dioxide (ETCO2). The sizing of the endotracheal tube is important in the pediatric population. Airway resistance is related to the diameter of the trachea, as described by the Poiseuille law, with resistance increasing to the fourth power of the radius. If there is minor swelling in an infant’s airway, it can lead to a marked increase in resistance. An endotracheal tube that is too large for an airway can press on the tracheal wall, leading to edema and even ischemia. Over the past 4 to 5 years, there has been a change in the clinical practice of pediatric anesthesia with the increased use of cuffed endotracheal tubes [31,32]. Potential advantages shown in comparison of the use of cuffed versus uncuffed endotracheal tubes include a reduction in the need to exchange the endotracheal tube, better airway seal providing improved respiratory mechanics, a more accurate ETCO2 tracing, and a decreased use of inhalational agents resulting in improved economics and less pollution of the operating rooms [33–35]. When dealing with the difficult airway, the major advantage of the use of a cuffed endotracheal tube is that the airway can be effectively sealed by slowly inflating the cuff even if the endotracheal tube does not totally occlude the airway. This advantage limits the need to switch to a larger endotracheal tube and repeat the procedure after the trachea is successfully intubated. In addition, because an endotracheal tube with a smaller ID can be used, it is likely to fit more easily through many of the airway devices and adjuncts that may be used for the difficult airway. The concerns regarding increased resistance of a smaller endotracheal have been virtually eliminated by the new generation of ICU ventilators, which are able to compensate for the smaller ID of cuffed endotracheal tubes by providing pressure support, thereby overcoming the increased work of breathing that they may impose. In specific intraoperative scenarios and in the ICU setting, the use of cuffed endotracheal tubes may also reduce the incidence and severity of aspiration in mechanically ventilated patients [36,37]. However, when cuffed endotracheal tubes are used, attention should be directed toward monitoring of the intracuff pressure [38]. In general, it is recommended that the intracuff pressure be maintained at less than 20 to 30 cm H2O, depending on the age of the patient. Airway and pulmonary parenchymal issues distal to the endotracheal tube Altered resistance and compliance can affect the efficacy of oxygenation and ventilation, and result most commonly from bronchospasm or alveolar space disease (pneumonia or noncardiogenic pulmonary edema). Other common

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causes include kinking of the endotracheal tube, main stem intubation, obstruction of the endotracheal tube with mucus or blood, or extrapleural problems including pneumothorax or hemothorax. Treatment is designed to identify the cause by ensuring that the endotracheal tube is clear of secretions, breath sounds are equal and bilateral, and that the placement of the tip of the endotracheal tube is midtrachea. Following these simple maneuvers, attention is directed at the treatment of bronchospasm as indicated and improvement of oxygenation and ventilation. Optimization of oxygenation depends on increasing the inspired oxygen concentration and maximizing mean airway pressure. A full description of the principles of mechanical ventilation and salvage techniques when conventional mechanical ventilation fails can be found elsewhere [39,40]. CLINICAL SCENARIOS The recognized difficult airway Based on the preoperative assessment of the airway, an airway may be determined to be potentially difficult. In such scenarios, there are 2 basic decisions to be made initially: 1. The route of endotracheal intubation: oral versus nasal 2. The level of consciousness: awake, sedated, or anesthetized

In most pediatric patients, the airway is instrumented after the induction of general anesthesia, which most commonly includes the administration of incremental concentrations of sevoflurane in 100% oxygen. This approach allows the maintenance of spontaneous ventilation until effective bag-valve-mask ventilation is possible. Spontaneous ventilation also allows the maintenance of oxygenation and ventilation while the airway is instrumented. Following the induction of anesthesia with spontaneous ventilation, there are many options for facilitating endotracheal intubation. These devices are discussed in more detail later. Some of the commonly used approaches include: 1. Indirect laryngoscopy with a commercially available device. The authors’ preference is the GlideScope (Verathon Inc, Bothwell, WA) (Fig. 1) or the C-MAC (Karl Storz, Tuttlingen, Germany) (Figs. 2 and 3). However, many other devices are available on the market. As with many airway devices, the clinician’s experience is likely to be more important than the specific device. 2. Placement of an LMA as a conduit for endotracheal intubation using fiberoptic guidance (Fig. 4). As an alternative, an intubating LMA can be used (Fig. 5). 3. Nasal or oral fiberoptic intubation. For a nasal or oral fiberoptic intubation, it is feasible to maintain general anesthesia by placement of a nasal airway into a naris. A 15-mm adaptor from an endotracheal tube is then attached to the nasal airway and connected to the anesthesia circuit. Sevoflurane in insufflated into the oropharynx, thereby maintaining anesthesia and oxygenation/ventilation. If a nasal fiberoptic is performed, a lubricated endotracheal tube is passed through the other naris and the bronchoscope passed through it and into the trachea. For oral fiberoptic intubation, an intubating oral airway is placed and the endotracheal tube and bronchoscope passed through it.

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Fig. 1. GlideScope blades and stylets.

4. Use of an optical stylet such as the Bonfils (Karl Storz, Tuttlingen, Germany) (Fig. 6). This stylet can be used to perform a retromolar intubation or can be combined with direct laryngoscopy and used as an optical stylet using a video screen. This technique is similar to the one commonly used by ENT surgeons, in which the rigid bronchoscope is placed through an endotracheal tube and the bronchoscope used to guide endotracheal intubation.

In rare circumstances, instrumentation of the airway is performed in the awake or sedated pediatric patient. In such cases, the use of airway blocks as an adjunct to sedation may be helpful [41,42]. In the pediatric patient, airway blocks are used less commonly. As an alternative, lidocaine (2%–4%) is aerosolized using a nebulizer in the same way that albuterol is administered. This method allows distribution of the local anesthetic agent throughout the airway.

Fig. 2. C-Mac blades (straight and curved).

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Fig. 3. Endotracheal intubation using the C-Mac videoscope system.

The administration of an anticholinergic such as glycopyrrolate is recommended 30 to 60 minutes earlier to dry the airway and allow better contact of the local anesthetic agent with the airway mucosa. Dosing should be limited to less than 5 mg/kg of lidocaine. The pediatric CICV scenario The cannot intubate–cannot ventilate (CICV) scenario is an anesthetic emergency requiring rapid and decisive management. The incidence of CICV events are difficult to estimate. Although various estimates have been provided for poor visualization during direct laryngoscopy (Cormack and Lehane grade 3 or 4), difficulties with endotracheal intubation occur in less than 5% of these cases. In addition, in those situations, failure to satisfactorily bag-mask ventilate, resulting in a CICV event, is even rarer, estimated at approximately 1 to 3 per 10,000 attempts [43]. However, the unanticipated CICV scenario, if not rescued promptly, can quickly result in severe complications, thereby

Fig. 4. A fiberoptic view of the glottis through the distal end of an LMA.

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Fig. 5. Fastrach intubating LMA.

making it the most frequent cause of anesthetic death [44]. Guidelines for managing the CICV have been published by the Canadian Task Force, the Difficult Airway Society, and the ASA [43–45]. These guidelines generally include recommendations for repeating direct laryngoscopy after changing head position and choice of laryngoscopy handle/blades. There also remains the caveat that repeated laryngoscopy is not recommended in the cannot intubate, but can ventilate scenario as repeated laryngoscopy may result in increasing airway edema result in the CICV scenario. The primary goals are maintenance of oxygenation and prevention of airway trauma. For the CICV scenario, the adult guidelines go on to recommend consideration for placement of an LMA, Combitube (Fig. 7), or needle cricothyrotomy with transtracheal jet ventilation. A review of the techniques and devices for transtracheal jet ventilation and cricothyrotomy in the pediatric patient can be found elsewhere [46]. Several factors mandate that the CICV algorithm be modified in the pediatric patient. As in the adult algorithm, an appropriate first step is the use of an LMA to provide oxygenation and ventilation. However, unlike the adult algorithm, given its restriction based on size, the Combitube is not generally recommended in the pediatric population. Furthermore, concern has recently been expressed

Fig. 6. Bonfils lighted stylet loaded with an endotracheal tube (the retromolar intubation endoscope).

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Fig. 7. Combitube.

regarding the recommendation for the use of needle cricothyrotomy and transtracheal jet ventilation. Unlike in the adult population, palpation of the cricothyroid membrane may be difficult in younger patients and placement of a catheter in the lumen of the trachea may be impossible. Given the risks of jet ventilation without a properly positioned catheter, the use of this rescue technique is not generally recommended in the young pediatric population [47]. It has been suggested that surgical cricothyrotomy is the invasive procedure of choice for emergency access of the airway in small children [48]. Although not currently included in the CICV algorithm of the ASA, we suggest consideration of the use of some form of indirect laryngoscope/video laryngoscope when faced with the CICV scenario. As an alternative, laryngoscopy with the use of a lighted stylet placed through an endotracheal tube or rigid bronchoscope should also be considered. Devices such as the GlideScope can be quickly brought into the room and prepared for use, generally in less than 60 seconds, allowing for their use even when faced with an unexpected scenario. These devices may have a place, especially in the pediatric CICV scenario following placement of an LMA and before surgical cricothyrotomy. Regardless of the sequence in which these devices are used, the first step in the algorithm should be to recruit additional support, including other pediatric anesthesiologists and pediatric otorhinolaryngologists. In the event of continued failure to establish ventilation, a decision to secure a surgical airway should not be delayed. In pediatric patients, the time available for rescue measures is less than in adults and surgical airway interventions are technically more difficult. Outcomes following emergency surgical airway interventions are poor, especially in neonates and infants. These situations are unforgiving and proper preparation and avoidance of the CICV scenario are of prime importance. EQUIPMENT FOR AIRWAY MANAGEMENT Anesthesia masks There are several designs of masks for bag-valve-mask ventilation. The shape of the mask and the self-inflatable sealing cuff are the main differences in

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design. Some clinicians prefer a more circular mask for young children. The face of a child is round and elongates over time. A round mask has a shorter anterior-to-posterior distance, which can lessen the likelihood of a gap at the mandible or pressure on the eyes. However, Infants have improved mask ventilation with an open mouth technique, which allows their large tongues to be off the palate, thereby opening the airway. Therefore the correct shape and size of the mask must be chosen for the specific patient (Fig. 8). The sealing cuff of the mask provides a soft surface that can seal the circuit to the patient. This seal allows positive pressure to be transmitted to the lungs and not lost to the atmosphere. Although the balloon seal may increase the dead space, which may affect small infants more than adults, the ease of creating a seal to provide CPAP and positive-pressure ventilation during induction is critical. In general, masks are clear to allow observation of the patient’s face and lips under the mask and for the presence of emesis. Laryngoscopes The shape and length of the laryngoscope are important components affecting the success rate for endotracheal intubation of infants and children. The most commonly used blades include the curved (Macintosh) and the straight (Miller) blades. The curved blade decreases the pressure placed on the tongue and applies most of the force to the vallecula to assist in the displacement of the epiglottis indirectly to create a view of the glottis. The Macintosh blade also has a flange that can control the tongue by sweeping it laterally. In small children the curved blade often fails to provide an adequate view for endotracheal intubation, especially if there is any degree of micrognathia. The Miller blade overcomes some of the challenges of the pediatric airway by manually lifting the epiglottis directly. Combinations of the effective features of the curved and straight blade have resulted in hybrid blades that are useful in various clinical scenarios in pediatric airway management. These blades include the

Fig. 8. Different sizes of disposable, clear anesthesia masks.

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Seward, Robertshaw, and the Wis-Hipple designs (Fig. 9). In general, these blades combine the flatter flange of the Macintosh (compared with the rounder flange of the Miller blade), albeit without its curve, while maintaining the flat distal end for placement on the laryngeal side of the epiglottis. Airway adjuncts Oral and nasal airways Airway adjuncts are tools that are used to ensure the patency of the airway during mask ventilation. The oral airway and nasal airway are commonly used to improve ventilation. Several sizes and styles are available for pediatric patients and may be used to overcome soft tissue obstruction of the upper airway (Fig. 10). The oral airway is designed to provide a conduit for airway movement through the oral cavity to posterior pharynx. The appropriate size should be used to minimize the chances of airway trauma or exacerbation of the airway obstruction (Fig. 11). Placement requires a deep enough plane of anesthesia or sedation to blunt protective airway reflexes to avoid precipitating laryngospasm. Nasal airways are flexible tubes that allow gas exchange through the nares and the posterior pharynx. They can traumatize the nares and lead to epistaxis if too large a size is used or following forcible placement against resistance (Fig. 12). An appropriate placement technique can generally avoid such problems with appropriate lubrication before placement. In addition, the topical application of a vasoconstrictor to the nasopharynx before placement may be helpful. This vasoconstrictor can include a topical spray such as oxymetazoline or the addition of a vial of phenylephrine (10 mg) to a topical lidocaine lubricant. Sizing is performed by measuring the distance from the nares to ear to the angle of the jaw. A nasal or oral airway that is too long may stimulate protective airway reflexes, inducing cough, or even precipitate laryngospasm. A nasal or oral airway that is too short does not provide an adequate conduit behind the tongue and is ineffective. As opposed to an oral airway, a nasal airway is generally well tolerated in the awake or lightly sedated patient.

Fig. 9. From left to right: Miller, Macintosh, Sheridan, and Wis-Hippel laryngoscope blades.

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Fig. 10. Different sizes of oral airways.

LMA The original version of the LMA was introduced into clinical practice in 1988 in the United Kingdom and in the United States in 1991. Several devices are now available with modifications, but the overall function has not changed. Following the introduction of the LMA Classic into common anesthesia

Fig. 11. Choosing the correct size for an oral airway: mouth to the angle of the mandible.

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Fig. 12. Choosing the correct size for a nasal airway: nares to the ear lobe.

practice, various manufacturers have developed modifications in an attempt to provide specific advantages in various clinical scenarios. The modifications to these devices from the LMA Classic include single-use disposable devices, a pilot cuff with color bands to measure pressure, removal of the aperture bars to facilitate passage of an endotracheal tube, esophageal sealing cuffs, an esophageal channel to allow passage of a nasogastric tube, gel cuffs, integrated bite blocks, and rigid curved shapes to facilitate placement [49,50]. The LMA and other supraglottic devices allow ventilation by moving soft tissue and the tongue while sealing the glottis, effectively masking the glottic opening. Over the years, there has been an expansion of these devices to cover the all pediatric ages and weights (Table 5). Pediatric supraglottic devices in Table 5 LMA sizes for pediatric patients LMA size

Weight (kg)

Cuff inflation (mL)

1 1.5 2 2.5 3 4 5

Less than 5 5–10 10–20 20–30 30–50 50–70 70–100

4 7 10 14 20 30 40

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common use include the LMA Classic, LMA Pro-seal, AES ultraCPV, Air-Q, Portex soft seal, i-gel, and the King LAD and LT-D. These supraglottic devices may be used as rescue devices in the CICV and also as a conduit for endotracheal intubation. When used for endotracheal intubation, various techniques are available. When first developed, the technique generally included blind placement of the endotracheal tube through the LMA and into the trachea. This technique led to the development of the intubating LMA for the adult population. Blind intubation through an LMA Classic with a 6-mm endotracheal tube in adult patients has been shown to be successful more than 90% of the time [51]. If the LMA is not perfectly aligned with the glottic opening, ventilation may be adequate but the endotracheal tube cannot be blindly passed into the trachea. In this scenario, there are options to facilitate placement of the endotracheal tube through the LMA, including repositioning of the LMA to a better position over the glottis opening. As an alternative, an endotracheal tube can be placed in the LMA and the fiberoptic bronchoscope passed through the endotracheal tube and into the trachea (see Fig. 4). Fiberoptic intubation through an LMA is discussed later. When passage of an endotracheal tube through an LMA is chosen, there may be advantages to the Air-Q LMA because it has been modified to facilitate placement of an endotracheal tube [52]. This newer version LMA has a removable 15-mm adaptor, a wider and shorter shaft, and no grill bars at the distal end to facilitate passage of an endotracheal tube (Figs. 13 and 14). Indirect laryngoscopy and video laryngoscopes Indirect laryngoscopy describes the use of equipment that provides a view of the larynx without aligning the oral cavity, pharynx, and larynx. Hence these devices are useful in situations that prevent the normal alignment of the oral, pharyngeal, and glottis structures including micrognathia, limited mouth opening, and restricted neck movement. This group of devices has had the greatest increase over the past 5 to 10 years with the introduction of a myriad of devices

Fig. 13. Relative length of forceps (top), endotracheal tube (middle), Air-Q LMA (bottom).

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Fig. 14. Intubation through the Air-Q LMA. Forceps can be used to hold the endotracheal tube in place and slide the Air-Q LMA over the endotracheal tube and the forceps.

[53–56]. Modifications and advancements have also facilitated the use of these devices in young and small pediatric patients [57]. Using video input that is transmitted to a screen, the view can be wider and more magnified than traditional direct laryngoscopy. Some video laryngoscopes use blades similar to traditional curved and straight blades, whereas others are modified. Benefits of video-assisted laryngoscopy include a more distal view on the scope, which can provide a view of the glottis even when not available from direct laryngoscopy; ability to view the advancement of the endotracheal tube through the vocal cords; and a screen so that many users can view at once. The multiperson view allows teaching during nonemergent situations. However, to facilitate the rapid transport of some of these devices, the screen has been kept small or incorporated into the device. Some of these devices are single use and disposable, whereas others need to be sterilized and reused. Various advantages and disadvantages have been reported when comparing these video laryngoscopes with each other as well as with traditional direct laryngoscopy [58–61]. Although a full review is beyond the scope of this article, as with many of the devices discussed in this article, the major factor in success seems to be the experience of the user rather than the specific device. Our belief is that some form of video laryngoscope should be in the CICV scenario following LMA placement and before invasive techniques such as needle or surgical cricothyrotomy. In our practice, these devices have significantly decreased the need for fiberoptic intubation of the trachea, and offer the significant advantage of being as efficient and facile as direct laryngoscopy. There is a specific need in pediatric video laryngoscopes for different sizes for the different age groups. The Airtraq is used like a Macintosh blade in the vallecula and has a channel into which a standard endotracheal tube is placed, which is meant to eliminate the need for a stylet. The distal tip of the GlideScope has a 60 curve, thereby providing an enhanced view for anterior airways. A stylet is often needed to facilitate passage of the endotracheal tube through the glottis and into the trachea. The C-MAC and Berci Caplan VL use blades that are similar to conventional Macintosh and Miller blades, which can

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improve a novice’s familiarity with the device and provide a teaching tool for the use of conventional blades. A stylet can help maneuver the endotracheal tube with these systems as well. The TruView EVO2 has a similar shape to a Miller 0-1 blade and has a side port for the insufflation of oxygen [61]. Fiberoptic bronchoscopy Flexible fiberoptic bronchoscopy is the traditional technique for securing an airway in an awake, spontaneously breathing patient with a known or anticipated difficult airway. The fiberoptic bronchoscope uses thin (fiberoptic) cables to transmit light to the airway structures and the image of the airway structures back to the video screen. Care must be taken to keep these cables intact. Breaking the fibers by excessive bending can decrease the image quality to the point at which it is no longer useful. Although the optics have improved over the past 10 to 15 years, airway secretions and blood are the greatest impediments to a successful image. Although frequently performed awake in the adult population, this is not generally feasible in the pediatric patient. Deep sedation or general anesthesia is generally required. The awake patient maintains airway muscle tone and spontaneous respirations, allowing time to view the airway structures and time to maneuver the scope into the trachea without oxygen desaturation. A patient who is deeply anesthetized loses airway muscle tone, which may result in the soft tissues of the pharynx and tongue falling together and obstructing the view with a fiberoptic bronchoscope. At times, airway displacement of the tongue with a standard laryngoscope or a forceps can be helpful. If a patient is apneic, there may not be enough time to view airway structures before desaturation. Therefore, the pediatric patient who does not tolerate awake endotracheal intubation must have a way to maintain oxygenation during the procedure. A description of a technique to allow general anesthesia with spontaneous ventilation for fiberoptic intubation of the trachea is outlined earlier. Fiberoptic-assisted intubation through an LMA is a technique that has gained widespread use in managing the difficult airway (see Fig. 4). The LMA eliminates some of the difficulty involved in the sedated or anesthetized patent with a difficult airway. The LMA provides a conduit for endotracheal intubation and can overcome soft tissue obstruction of the upper airway. When positioned correctly, the LMA advances the tongue anteriorly and the soft tissue of the posterior pharynx caudally, leaving an unobstructed view of the glottis for fiberoptic intubation. The LMA also provides an airway that can be used to ventilate and oxygenate either spontaneously or with positive-pressure ventilation. Removal of the LMA after placement of the endotracheal tube through it can be problematic. The Air-Q has a large internal lumen so that the endotracheal tube and the pilot balloon can fit through it. A bougie can be placed through the LMA or small forceps can be used to maintain the placement while removing the LMA (see Fig. 14). As an alternative, the cuff of the LMA can be deflated and the LMA left in place during the procedure. We recommend the use of extralong endotracheal tubes, known as microlaryngoscopy tubes

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Fig. 15. Relative length of microlaryngeal tube (top) and conventional endotracheal tube (bottom).

(Fig. 15), which come in pediatric diameters with a standard adult length, thereby allowing extra distance beyond the tip of the LMA (Fig. 16). Optical stylets Optical stylets are lighted rigid or semirigid stylets with the capability of directly viewing airway anatomy while aiding in intubation [54,62]. The rigidity of the stylet can displace the relaxed soft tissue of an anesthetized apneic patient. A learning period for optical stylets of approximately 20 intubations has been suggested before the practitioner is competent in the use of such devices in a difficult airway scenario. Placement of the endotracheal tube on an optical stylet allows the practitioner to view a small rim of the tube distal to the stylet, which allows visual confirmation of the placement of the endotracheal tube into the trachea. Unlike the flexible fiberoptic bronchoscope, with which the endotracheal tube is advanced over the bronchoscope, the optical stylets allow visually assisted manipulation, which may be helpful when resistance to advancement of the endotracheal tube is noted. Although many of these devices can be used without a laryngoscope (using the so-called retromolar approach), the technique for endotracheal intubation is often improved with a direct view of the epiglottis. This view can be achieved with direct laryngoscopy or an adequate jaw thrust. A 2-person technique often helps with this because one provider can perform the

Fig. 16. Intubation through the LMA using the microlaryngeal tube.

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direct laryngoscopy while the other manipulates the optical stylet. A left molar approach has been reported with a higher success rate with novice users with certain stylets [63,64]. The Bonfils endoscopes have a 40 anterior curve and are rigid (see Fig. 6) [65]. The manufacturer recommends a retromolar approach. An oxygen port located on the rear of the scope can provide low-flow oxygen to a spontaneously ventilating patient and blow secretions off the tip of the stylet for a better view [65]. Flows of less than 3 L/min are recommended. The use of insufflating oxygen in small children and infants may increase the risk of pneumothorax [66]. Shikani optical stylets have a semirigid stylet that can be adjusted based on the shape of the patient’s airway. Midline insertion has been recommended with the Shikani optical stylet. Because the stylet is advanced over the tongue in the midline, the uvula should come into view. A view of the uvula is important to maintain midline advancement because once the tip of the stylet is out of view it can slip laterally. The midline movement is continued until the tip is past the epiglottis and just past the vocal cords. At this point the tube can be advanced over the stylet. Light wands and stylets A bright light that can be visualized entering the trachea when viewed from the anterior aspect of the neck is another device that has been reported for use in patients with a difficult airway. These devices have seen greatest use in the adult population, with few reports of their use in infants and children. Even when secretions or blood impair a direct or indirect view of the larynx, a lighted stylet may be effective. The light wand is a rigid stylet that directs light through fiberoptic fibers to its tip. The device is placed through a standard endotracheal tube so that the light shines at the distal end. The room lights should be dimmed during insertion because this significantly improves the viewing of correct placement. Because the trachea is more superficial (than the esophagus) and midline, the light is bright red as it travels from the supraglottic area to the trachea. The light seen in the neck should not deviate off midline as it is advanced, or decrease in brightness. The latter indicates passage into the esophagus. Likewise, it should not be advanced against resistance. The device is inserted midline into the mouth and along the back of the oropharynx so that the light can be seen midline along the anterior surface of the neck. Slight anterior angulation of the distal tip can be used to guide its movement into the trachea. If the trachea is deviated or there is a mass anterior to the trachea (goiter), the use of the lighted stylet becomes difficult. Once the tip of the stylet is in the trachea, the endotracheal tube is advanced blindly off the stylet. If resistance is met, care must be taken not to dislodge the lighted stylet from the trachea or to cause trauma to the airway. Catheters and bougies Catheters and bougies can be used as guides to intubate the trachea or as a means to exchange an already present endotracheal tube. Different sizes and types of catheters facilitate use in all age groups [67]. A bougie is commonly

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used to facilitate direct laryngoscopy when the larynx is anterior and an effective view of the glottic opening cannot be achieved. The bougie is generally stiffer than an exchange catheter, with a 30 to 45 anterior bend at the distal tip to facilitate placement underneath the epiglottis. The stiffness of the catheter allows the provider to gain tactile sense as the tip engages the various tracheal rings, thereby confirming its location. The endotracheal tube is then placed over the bougie. Many of the exchange catheters have a ventilating port that allows the insufflation of oxygen without an endotracheal tube. When used in the difficult airway algorithm, a correctly placed catheter with a ventilating channel may allow oxygenation. However, as noted earlier, the use of oxygen insufflation, especially at high flow rates, may result in barotrauma. In addition, care must be taken to minimize trauma to the airway when inserting airway catheters. Another common use for exchange catheters is for tracheal extubation of a known difficult airway, which includes patients with recent craniofacial surgery with swelling affecting the airway. In this scenario, the exchange catheter is placed through the endotracheal tube and then left in place in the trachea following tracheal extubation. If reintubation becomes necessary, the airway catheter allows a track over which to railroad the endotracheal tube. The emergency airway cart A pediatric institution must take into consideration the varying ages and sizes of patients. Many institutions (including ours) have a specific difficult airway cart with a full array of all of the equipment that is discussed in this article. The cart can also have a video screen attached to it for use with a fiberoptic bronchoscope or a video laryngoscope. The key to the successful use of a difficult airway cart is its availability and the proficiency of the staff in using it. Training in set-up and use must be performed in a nonemergent setting to improve the morbidity and mortality of the pediatric patient with a difficult airway (Fig. 17). FUTURE TRENDS Emerging technologies and advancements in airway assessment and endotracheal intubation techniques will continue to evolve. As they do, the anesthesia practitioner must continue to be knowledgeable of and trained in the emerging devices and techniques. Such training should be performed in a nonemergent setting before using a technique or device in an emergent situation. A promising future development is the use of ultrasound in assessing the airway. Ultrasound can be used to visualize airway structures in real time, identifying potential difficulties. It can also be used to visualize movement of an endotracheal tube within the trachea and offers the possibility of not only guiding placement but also confirming it in real time [68,69]. Improvements in pharmacology may also aid emergency airway management. Although succinylcholine is frequently chosen given its rapid offset, even with a recovery time of 6 to 8 minutes, profound hypoxemia and death

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Fig. 17. Difficult airway cart with various airway adjuncts and instruments, medications, and provision for fiberoptic bronchoscopy and indirect laryngoscopy.

may occur in this period of time in the difficult airway scenario including the CICV situation. The introduction of sugammadex into the clinical market offers the theoretic potential to rapidly reverse the nondepolarizing, aminosteroid neuromuscular blocking agent, rocuronium, which could be beneficial in the unanticipated difficult airway when a neuromuscular blocking agents has been administered and the patient becomes difficult to ventilate [70,71]. SUMMARY The pediatric patient with a difficult airway presents unique challenges that must be addressed with multiple strategies to ensure a safe outcome. The approach to the pediatric patient with a potentially or documented difficult airway begins with preparation, including a thorough preoperative assessment of the airway and the ready availability of the equipment needed to intervene. Many of the approaches to the pediatric patient with a difficult airway may include anesthetic induction with the maintenance of spontaneous ventilation followed by airway instrumentation. The use of a readily available difficult airway cart with a trained team of professionals can significantly improve morbidity and mortality of the pediatric difficult airway. Consultation with and involvement of pediatric otolaryngology colleagues is frequently helpful

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in dealing with such patients. Because seconds matter in a hypoxemic patient, training must be maintained with current devices and techniques in nonemergent settings. References [1] Hernrich S, Birkholz T, Ilmsen H, et al. Incidence and predictors of difficult laryngoscopy in 11,219 pediatric anesthesia procedures. Paediatr Anaesth 2012;22:729–36. [2] Mirghassemi A, Soltani A, Abtahi M. Evaluation of laryngoscopic views and related influencing factors in a pediatric population. Paediatr Anaesth 2011;21:663–7. [3] Frei FJ, Ummenhofer W. Difficult intubation in paediatrics. Paediatr Anaesth 1996;6: 251–63. [4] Butler MG, Hayes BG, Hathaway MM, et al. Specific genetic diseases at risk for sedation/ anesthesia complications. Anesth Analg 2000;91:837–55. [5] Woodall NM, Cook TM. National census of airway management techniques used for anesthesia in the UK: first phase of the Fourth National Audit Project at the Royal College of Anesthetists. Br J Anaesth 2011;106:266–71. [6] Cook TM, Woodall N, Harper J, et al. Fourth National Audit Project. Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anesthetists and the Difficult Airway Society. Part 2: intensive care and emergency departments. Br J Anaesth 2011;106:632–42. [7] Easley RB, Segeleon JE, Haun SE, et al. Prospective study of airway management of children requiring endotracheal intubation before admission to a pediatric intensive care unit. Crit Care Med 2000;28:2058–63. [8] Bhananker SM, Ramamoorthy C, Geiduschek JM, et al. Anesthesia-related cardiac arrest in children: update from the pediatric perioperative cardiac arrest registry. Anesth Analg 2007;105:344–50. [9] Jimenez N, Posner KL, Cheney FW, et al. An update on pediatric anesthesia liability: a closed claims analysis. Anesth Analg 2007;104:147–53. [10] Heinrich S, Birkholz T, Irouschek A, et al. Incidences and predictors of difficult laryngoscopy in adult patients undergoing general anesthesia. J Anesth, in press. [11] Uezono S, Holzman RS, Goto T, et al. Prediction of difficult airway in school-aged patients with microtia. Paediatr Anaesth 2001;11:409–13. [12] Magalha ˜ es E, Oliveira MF, Sousa Goveˆia C, et al. Use of simple clinical predictors on preoperative diagnosis of difficult endotracheal intubation in obese patients. Rev Bras Anestesiol 2013;63:262–6. [13] Kim WH, Ahn HJ, Lee CJ, et al. Neck circumference to thyromental distance ratio: a new predictor of difficult intubation in obese patients. Br J Anaesth 2011;106:743–8. [14] Wilson ME, Spiegelhalter D, Robertson JA, et al. Predicting difficult intubation. Br J Anaesth 1988;61:211–6. [15] Shiga T, Wajima Z. Predicting difficult intubation in apparently normal patients: a metaanalysis of bedside screening test performance. Anesthesiology 2005;103:429–37. [16] Hampson-Evans D, Morgan P, Farrar M. Pediatric laryngospasm. Paediatr Anaesth 2008;18:303–7. [17] Tait AR, Malviya S, Voepel-Lewis T, et al. Risk factors for perioperative adverse respiratory events in children with upper respiratory tract infections. Anesthesiology 2001;95: 299–306. [18] Van der Walt J. Anesthesia in children with viral respiratory tract infections. Paediatr Anaesth 1995;5:257–61. [19] Orliaguet GA, Gall O, Savoldelli GL, et al. Case scenario: perianesthetic management of laryngospasm in children. Anesthesiology 2012;116:458–71. [20] Schreiner MS, O’Hara I, Markakis DA, et al. Do children who experience laryngospasm have an increased risk of upper respiratory tract infection? Anesthesiology 1996;85: 475–9.

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[21] Burgoyne LL, Anghelescu DL. Intervention steps for treating laryngospasm in pediatric patients. Paediatr Anaesth 2008;18:297–302. [22] Afshan G, Chohan U, Qamar-Ul-Hoda M, et al. Is there a role of a small dose of propofol in the treatment of laryngeal spasm? Paediatr Anaesth 2002;12:625–8. [23] Batra YK, Ivanova M, Ali SS, et al. The efficacy of a subhypnotic dose of propofol in preventing laryngospasm following tonsillectomy and adenoidectomy in children. Paediatr Anaesth 2005;15:1094–7. [24] Hannallah RS, Oh TH, McGill WA, et al. Changes in heart rate and rhythm after intramuscular succinylcholine with or without atropine in anesthetized children. Anesthesiology 1986;65:1329–32. [25] Al-Alami AA, Zestos MM, Baraka AS. Pediatric laryngospasm: prevention and treatment. Curr Opin Anaesthesiol 2009;22:388–95. [26] Walker RM, Sutton RS. What port in a storm? Use of suxamethonium without intravenous access for severe laryngospasm. Anaesthesia 2007;62:757–9. [27] Tobias JD, Nichols D. Intraosseous succinylcholine for orotracheal intubation. Pediatr Emerg Care 1990;6:108–9. [28] Tobias JD, Ross AK. Intraosseous infusions: a review for the anesthesiologist with a focus on pediatric use. Anesth Analg 2010;110:391–401. [29] Reynolds LM, Lau M, Brown R, et al. Intramuscular rocuronium in infants and children. Anesthesiology 1996;85:231–9. [30] Weiss M, Engelhardt T. Cannot ventilate-paralyze! Paediatr Anaesth 2012;22: 1147–9. [31] Weiss M, Dullenkopf A, Fischer JE, et al, European Paediatric Endotracheal Intubation Study Group. Prospective randomized controlled multi-centre trial of cuffed or uncuffed endotracheal tubes in small children. Br J Anaesth 2009;103:867–73. [32] Weiss M, Dullenkopf A. Cuffed tracheal tubes in children: past, present and future. Expert Rev Med Devices 2007;4:73–82. [33] Eschertzhuber S, Salgo B, Schmitz A, et al. Cuffed endotracheal tubes in children reduce sevoflurane and medical gas consumption and related costs. Acta Anaesthesiol Scand 2010;54:855–8. [34] Khine HH, Corddry DH, Kettrick RG, et al. Comparison of cuffed and uncuffed endotracheal tubes in young children during general anesthesia. Anesthesiology 1997;86:627–31. [35] Lo ¨ nnqvist PA. Cuffed or uncuffed tracheal tubes during anaesthesia in infants and small children: time to put the eternal discussion to rest? Br J Anaesth 2009;103:783–5. [36] Bernhard WN, Cottrell JE, Sivakumaran C, et al. Adjustment of intracuff pressure to prevent aspiration. Anesthesiology 1979;50:363–6. [37] Spray SB, Zuidema GD, Cameron JL. Aspiration pneumonia; incidence of aspiration with endotracheal tubes. Am J Surg 1976;131:701–3. [38] Tobias JD, Schwartz L, Rice J, et al. Cuffed endotracheal tubes in infants and children: should we routinely measure the cuff pressure? Int J Pediatr Otorhinolaryngol 2012;76: 61–3. [39] Tobias JD. Conventional mechanical ventilation. Saudi J Anaesth 2010;4:86–98. [40] Thung AK, Hayes D Jr, Preston TJ, et al. Respiratory support including emergent extracorporeal membrane oxygenation as a bridge to airway dilatation following perioperative bronchial occlusion. Middle East J Anesthesiol 2012;21:879–88. [41] Nibedita P, Rath SK. Regional and topical anaesthesia of the upper airways. Indian J Anaesth 2009;53:641–8. [42] Simmons ST, Schleich AR. Airway regional anesthesia for awake fiberoptic intubation. Reg Anesth Pain Med 2002;27:180–92. [43] Crosby ET, Cooper RM, Douglas MJ, et al. The unanticipated difficult airway with recommendations for management. Can J Anaesth 1998;45:757–76. [44] Henderson JJ, Popat MT, Latto IP, et al. Difficult Airway Society guidelines for management of the unanticipated difficult intubation. Anaesthesia 2004;59:675–94.

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