Airway management in infants and children

Best Practice & Research Clinical Anaesthesiology Vol. 19, No. 4, pp. 675–697, 2005 doi:10.1016/j.bpa.2005.07.002 available online at http://www.sciencedirect.com

9 Airway management in infants and children Ansgar M. Brambrink*

MD, PhD

Associate Professor for Anesthesiolgy and Peri-Operative Medicine Department of Anesthesiology and Peri-Operative Medicine, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Mail Code: UHS-2, Portland, OR 97239-3098, USA

Ulrich Braun

MD, PhD

Professor Emeritus for Anesthesiology Department of Anesthesiology, Rescue and Intensive Care Medicine, Georg-August-Universitaet Go¨ttingen, Universitaetsklinikum, D-37099 Go¨ttingen, Germany

Anaesthesiologists, paediatricians, paediatric intensivists and emergency physicians are routinely challenged with airway management in children and infants. There are important differences from adult airway management as a result of specific features of paediatric anatomy and physiology, which are more relevant the younger the child. In addition, a number of inherited and acquired pathological syndromes have significant impact on airway management in this age group. Several new devices—e.g. different types of laryngeal mask airways in various sizes, small fibre-endoscopes—have been introduced into clinical practice with the intention of improving airway management in this age group. Important new studies have gathered evidence about risks and benefits of certain confounding variables for airway problems and specific techniques for solving them. Airway-related morbidity and mortality in children and infants during the perioperative period are still high, and only a thorough risk determination prior to and continuous attention during the procedure can reduce these risks. Appropriate preparation of the available equipment and frequent training in management algorithms for all personnel involved appear to be very important. Key words: children; neonates; airway management; paediatric anaesthesia; paediatric face masks; conventional endotracheal intubation; cuffed endotracheal tubes; perioperative airway risks; laryngeal mask airway; laryngeal tube; fibre-optic intubation; paediatric fibre-endoscope; craniofacial malformations.

One key competence of an anaesthesiologist is securing the airway in patients of all age groups. Anatomical and physiological differences between infants, children and adults also extend to the airway. Thus, airway management in younger patients requires special expertise and familiarity with the equipment available. Of great concern are

* Corresponding author. Tel.: C1 503 494 7641; Fax: C1 503 494 6482. E-mail address: [email protected] (A.M. Brambrink).

1521-6896/$ - see front matter Q 2005 Elsevier Ltd. All rights reserved.

676 A. M. Brambrink and U. Braun

anatomical variations or pathological conditions of the airway, perhaps previously unrecognized in a young patient, which make routine airway management impossible after induction of anaesthesia or during emergency care. There have been major improvements in this field over the years, such as the implementation of the laryngeal mask airway (LMA) into the algorithms of routine and difficult airway management in children, as well as the increasing availability of fibreoptic intubation even for infants. As of today, however, the routine airway in infants and the management of expected and unexpected difficult airways in children of all ages still present one of the major challenges to every anaesthesiologist, paediatrician and emergency physician.1 This chapter summarizes the anatomical and physiological characteristics of the paediatric airway, provides an update of currently available paediatric airway equipment (including supraglottic airway devices and fibre-endoscopes in this age group), and explains pathological conditions which are typically associated with a difficult airway in children and infants. SPECIAL ANATOMICAL AND PHYSIOLOGICAL CONSIDERATIONS Mature and premature newborns breathe exclusively through their noses, which may result in critical respiratory problems in children with, for example, bony or membranous choanal atresia.2,3 The trachea length in preterm neonates is only 2–3 cm (25th and 35th weeks postconceptional age, respectively)4, and at term only 4 cm, and so a meticulous positioning of the endotracheal tube is required to avoid endobronchial dislocation or accidental extubation during subsequent manipulations etc. The position of the larynx is relatively higher than that in adults; in the newborn, computed tomography (CT) or magnetic resonance imaging (MRI) scans reveal the larynx at the C4 level5 as compared to C6–7 in the adult. This might be associated with difficulties during endotracheal intubation, especially in very young patients. Positional airway obstruction in unintubated neonates may occur in the supine position by posterocephalic displacement of the mandible, leading to narrowing of the upper airway6 or, if intubated with an uncuffed endotracheal tube, by abutment of the bevelled distal endotracheal tube orifice against the tracheal wall.7 This can be relatively easily prevented by providing appropriate neck and head support, such as foam/gel rolls or cushions. Newborns have an increased metabolic rate which results in a significantly greater need for oxygen than that in adults (6–7 mL/kg per minute versus 3–4 mL/kg per minute), leading to a decreased mixed venous return and a proportionally decreased tolerance to apnoea. In addition, the residual capacity is much smaller at this age than that in the adult. The relation between alveolar ventilation (VA) and residual capacity (FRC) is 5:1 in newborns versus 1:1.5 in the adult, resulting in a significantly smaller relative volume to store oxygen, e.g. prior to induction of anaesthesia. Even with adequate preoxygenation, arterial oxygenation (SaO2) may decrease below 90% even after 100 seconds in newborns, whereas in the same experimental setting school-age children kept their saturation above that level for at least 400 seconds.8 In clinical practice, optimal preoxygenation is often difficult to achieve (e.g. combative child with an air-tight face mask), and the risk for rapid desaturation is even higher. This requires rapid and accurate airway management in this age group. Newborns also produce CO2 at a much higher rate and require a higher alveolar ventilation than adults (100–150 mL/kg per minute versus 60 mL/kg per minute). Due to their small lung volumes, this can only be achieved by a significantly increased respiration rate (30–40/minute in newborn, 20–30/minute in infants).

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The thorax of a newborn is bell-shaped and cartilaginous, and therefore much softer than in the adult. The ribs are horizontally oriented, the epigastric angle is obtuse, and the abdominal organs are relatively large. This does not allow for much extension of the diaphragm during ventilation with small airway pressures, and this, together with the relatively high lung compliance (0.06 mL/cmH2O in the newborn versus 0.04 mL in the adult), results in a higher risk of pulmonary overextension in newborns and infants, e.g. with manual ventilation during induction of anaesthesia. Practice points † newborns are exclusive nose-breathers, the larynx position is high, and the trachea is short, all of which may result in difficulties in managing the airway during the perioperative period † positional obstruction of the airway is more frequent in small children and infants, and requires more emphasis on appropriate neck and head support † increased metabolic rate, smaller relative volume to store oxygen, and difficulties in providing optimal preoxygenation result in an overall higher risk for critical desaturation during the perioperative period in young children; the younger the child, the more concern should be applied, and the more experience is required to provide safe anaesthesia care

Research agenda † to determine the incidence of critical desaturation and dangerous hypoxic complications during induction of anaesthesia in small children and infants in the routine clinical setting (large multicentre studies are required) † to evaluate the incidence of difficulties with mask-bag ventilation, tracheal intubation and mechanical ventilation in small children and infants (similarly, voluminous studies would be beneficial)

FACE MASKS IN INFANTS AND CHILDREN The face mask represents the simplest man-to-machine interface for oxygenating and ventilating a patient. For adequate ventilation, the face mask should be of appropriate size to allow for a perfect seal around mouth and nose, and the best-fitting mask needs to be determined for every child (Table 1). Successful ventilation using a face mask also depends on the optimal position of the patient’s head (e.g. the modified Jackson position allows for a stretch in the airway). Long-term face-mask ventilation carries a significant risk for gastric insufflation, especially in the infant (see above). Compared to the endotracheal tube, applying a face mask significantly increases dead space. The smaller the patient, the greater this concern is. Randell–Baker/Soucek masks were designed to minimize mechanical dead space according to the facial contours of children.9 In addition, they are made of lightweight and transparent material, allowing for observation of perioral skin colour and the humidity of the expired gases, and for the immediate recognition of oral or gastric secretions. Children with anatomical or

678 A. M. Brambrink and U. Braun

Table 1. Oral airway and face masks for use in infants and children. Oral airway (Guedel tube)

Face mask (Randell–Baker)

Age

Size

cm

Size

Dead space (mL)

Preterm Neonate (0–3 months) Infant (3–12 months) Toddler (1–5 years) School age (5–12 years) Teenager (O13 years)

000 00 0 1 2 3

3.5 4.5 5.5 6.0 7.0 8.0

0 1 1–2 2 3 n/a

2 4 4; 8 8 15 n/a

n/a, not applicable.

mechanical problems interfering with an appropriate face-to-mask seal (e.g. an oralgastric feeding tube) may benefit from clear plastic masks with soft inflatable cuffs which allow adaptation to the individual needs. If fibrescopic intubation is considered, a specially designed clear plastic face mask provides an extra port which allows the passage of the endoscope while providing a means for oxygenation, ventilation and anaesthetic gases during the procedure.10 Alternatively, the Mainz universal airway adapter may be used.11 In young children, face masks are frequently used in conjunction with an oral airway, because their relatively large tongue may obstruct the airway during unconsciousness. Most commonly the smooth Guedel airway is used in children, but caution must be taken to use the proper size so as not to damage laryngeal structures or obstruct venous and lymphatic drainage, which may all result in postoperative airway swelling.12 In most cases, the appropriate size of oral airway for an individual child is equivalent to the distance between the mouth and the angle of the mandible. Table 1 summarizes appropriately sized face masks and oral airways for the different age groups. Practice points † for every child the best-fitting mask needs to be determined on an individual basis † face masks increase dead space significantly; the smaller the patient, the greater the concern † children with anatomical or mechanical facial abnormalities may benefit from clear plastic masks with soft inflatable cuffs, which allow adaptation to the individual’s needs † specially designed clear plastic face masks are recommended for fibrescopic intubation † oral airways may cause airway obstruction in the unconscious child due to the relatively large tongue

Research agenda † to evaluate the incidence of difficult mask-bag ventilation in children † to evaluate the influence of positional changes and different face mask designs on success with mask-bag ventilation in infants and small children

Airway management in infants and children 679

LARYNGEAL MASK AIRWAY The laryngeal mask airway (LMA) was invented by A. I. J. Brain between 1980 and 1988, and was then released in the UK and later worldwide. The classic LMA was modified for special purposes according to the design criteria of the instrument. The flexible LMA was available in 1992, the intubating LMA in 1997, the disposable LMA in 1998 and the Proseal LMA in 2000. The inventor decided to try a scaled-down version of the adult LMA version for paediatric use. Today size 3 is considered a paediatric version. There are no paediatric sizes of the intubating or disposable LMAs. For paediatric application the classic LMA is available in sizes 1, 1.5, 2, 2.5 and 3, the flexible LMA and the Proseal LMA in all sizes except 1 and 1.5. Most studies with more than 500 investigated children claim that the LMA is safe and effective for children.13–18 It was a special experience to introduce and observe the LMA in children. The non-invasiveness of the device was very convincing for an experienced anaesthesiologist for whom coughing belonged to anaesthesia like pain to surgery. Before insertion of the LMA, preoxygenation should be provided. Propofol is a suitable induction agent for children, but the dose is much higher than in adults. Unpremedicated children require at least 4 mg/kg (rather than 2 mg/kg in the adult patient) and the dose should be titrated according to the clinical response.19 The target propofol concentrations are in the range of 8–14 mg/mL in children, compared to 6– 10 mg/mL in adults.19 Propofol and sevoflurane provide similar induction conditions, but hypotension may be more common after propofol.19 Data in the literature suggest that analgesic coinduction agents facilitate LMA insertion. The original Brain insertion technique as described in 198320 is recommended, and can be used for the classic, the disposable and the flexible LMA. The deflated cuff is introduced by placing the head and neck in the usual intubating position and applying pressure on the hard palate with the finger-pencil grip. The instrument is moved forward in the midline after lubrication. Variations of the original insertion technique are the lateral approach and the thumb technique. The original Brain technique is successful in a very high percentage of all cases, but on the other hand there is no evidence up to now that it guarantees a higher rate of correct positioning than alternative techniques. Therefore partial filling of the cuff and laryngoscope-guided insertion may be used if the classical technique fails. For the Proseal LMA laryngoscope guidance can be advocated by mounting the LMA on a gastric tube (GT), introducing the GT with the laryngoscope and letting the LMA slip in place via the GT. This technique is very promising for the Proseal LMA because it provides a forward movement into a good position by using a railroad. Cuff inflation should be provided with the minimal volume to form an effective seal. Bite blocks are recommended except for the Proseal LMA, which has an integrated bite block. Oropharyngeal leak pressure is around 20 cmH2O in children.19 Haemodynamic responses are lower for LMA insertion than for conventional laryngoscopic tracheal intubation.19 Airway-protective reflex activation with the LMA is not as frequent as with tracheal intubation.19 Medical imaging studies and case reports suggest that the LMA is frequently poorly positioned in children but gas exchange is unaffected.21–24 The use of muscular relaxation is not mandatory. Spontaneous ventilation and positive-pressure ventilation are both used extensively in children. It is important to avoid superficial levels of anaesthesia, because the larynx can always go into spasm at surgical or other stimulations. In theory, removal of the LMA should be preferred awake, after the

680 A. M. Brambrink and U. Braun

reflexes such as swallowing reappear. In practice, investigators have shown that there are no differences between awake and deep removal25,26, and that deep removal causes less coughing and less hypoxia.27–30 The LMA may be applied for difficult airway problems and for resuscitation, where it is effective in normal and low-birth-weight neonates19, but it may also be applied in the normal paediatric population. There may be more complications in infants and neonates if the LMA is applied for anaesthesia. The success rate of correct placement is lower than in older children, and gastric insufflation and laryngospasm are more frequent.19 This may be due to anatomical differences and to the fact that a deep level of anaesthesia is necessary and much more difficult to reach and maintain than in older children. The LMA can be used for cardiovascular and urological examination, dental surgery, endoscopy (tracheobronchoscopy, gastroscopy), ENT, general, orthopaedic or plastic surgery, ophthalmic surgery, medical imaging, radiotherapy and interventional radiology and tracheostomy.19 Other supraglottic airway devices have been devised for paediatric use, also with all paediatric sizes available. These are the soft-seal laryngeal mask (Portex, UK) and the laryngeal tube airway (VBM, Germany). There are no studies yet on either of these. The cuffed oropharyngeal airway (COPA, Mallinchrodt Medical, Ireland) was studied for use in paediatric patients19, but the device has been withdrawn by the manufacturer and is no longer available for clinical use. More studies are required to find out whether the alternative paediatric oropharyngeal airways other than the LMA are safe and effective for clinical use.

Practice points † LMAs are now available for all age groups † LMA placement in children is facilitated by using propofol and an appropriate dose of an analgesic drug for induction of anaesthesia; the classical insertion technique is recommended † the Proseal LMA is easily placed using a laryngoscope and after mounting the LMA onto a gastric tube; it is now available for almost all age groups † the LMA is frequently badly positioned in younger children, but gas exchange is unaffected; complications have been reported more frequently when the LMA is used in infants † the LMA may be applied for various situations involving a difficult airway in children and during resuscitation, e.g. in infants † alternative supraglottic airway devices for use in children and infants are the soft-seal laryngeal mask and the laryngeal tube airway

Research agenda † to determine the applicability and safety of alternative supraglottic airway devices when used in small children and infants

Airway management in infants and children 681

CONVENTIONAL ENDOTRACHEAL INTUBATION IN PAEDIATRIC PATIENTS The list of indications for an endotracheal intubation in children is similar to that for adults, i.e. endotracheal intubation is considered the gold standard for protecting the airway from aspiration, assuring adequate ventilation in the critically ill child (e.g. with pneumonia), and securing the airway during emergencies. Endotracheal intubation may be beneficial for infants as they are more likely to develop upper airway obstruction and gastric distention with longer periods of mask ventilation than are older children. (Detailed descriptions of standard equipment and techniques are available in the relevant chapters in current text books.31–33) However, laryngospasm or bronchospasm, airway oedema and postoperative tracheal stenosis have been associated with endotracheal intubation, especially in young children, and the potential risk factors require careful consideration. Areas of concern are the child’s current medical condition, materials used, co-medication, and the work environment in which airway management is performed. Upper respiratory tract infection (URTI) There is increasing evidence to suggest that children with URTIs carry an increased risk for respiratory complications when endotracheal intubation is performed.34–45 Additional risk factors include second-hand smoke, nasal congestions, copious secretions and productive cough, history of reactive airway disease, prematurity, snoring, surgery involving the airway, and anaesthetic technique (thiopental, residual muscle relaxant activity36,37). Even though the more severe complications—e.g. laryngospasm or bronchospasm—are rare, and a direct association remains controversial36,37, less severe complications seem to occur two to three times more frequently following endotracheal intubation in children with URTI for a period of at least 4 weeks after the infection.36,41,42,44 However, surgery may be performed even as an outpatient procedure if an experienced anaesthesiologist is providing perioperative care.34 If suitable for the procedure, these children may benefit from the use of an LMA for perioperative airway management.38,46 Regardless of these means, the elevated risks must be weighed on an individual basis against the potential benefit of a 4-week surgery delay, and should be discussed in detail with parents and surgeons. Endotracheal tube size The endotracheal tube itself poses resistance to airflow which is inversely proportional to the fourth power of the radius and directly proportional to the length, i.e. the narrower and longer the tube, the larger the flow resistance. This is of significant clinical importance for children during anaesthesia or intensive care, and ideally would require the widest and shortest possible breathing tube to be placed into the trachea. However, a child’s trachea is small, and its smallest diameter is at the level of the ring cartilage (cricoid ring), making it more funnel-shaped than an adult’s, and the narrowest aspect cannot been seen during conventional laryngoscopy. A tightly fitting endotracheal tube can easily result in decreased mucosal perfusion and subsequent oedema. The younger the child, the smaller the degree of subglottic oedema which already may result in critical airway obstruction and associated syndromes, e.g. dyspnoea, hypoxaemia, anxiety/panic, and the potential need for invasive management.

682 A. M. Brambrink and U. Braun

Finally, even cartilage damage may occur, potentially resulting in life-long impairment and disability, although no study has proved an association. Selection of the correctly sized endotracheal tube is facilitated by several formulae, the most widely accepted of which is related to the age of the child (inner diameter [ID] in mmZ(16Cage in years) /447,48, which was modified to: ID in mmZ(age in years/4)C4.49 This calculation overestimates the correct size in more than one in four cases50, meaning that it is necessary to have a one-size-smaller tube available at all times. Others have suggested a more conservative formula—ID in mmZ(age in years/4)C3.5—which may in fact result in a higher incidence of selections of tubes which are too small.31 Some emergency physicians and paramedics calculate tube size according to the height of the child (e.g. Broselow tape), which results in a similar predictive value (55% correct), but in contrast an erroneous prediction usually results in a smaller tube, which implies a reduced risk for airway injury.51 Current recommendations to determine the correct size of cuffed endotracheal tubes for children again relate to age. Either the standard formula (above) is applied and the predicted inner diameter size is reduced by 0.5 or 1.0 mm, or adapted formulae are used: e.g. ID in mmZ(age in years/4)C3.49 However, selecting the correct tube size in children may be much more complex, leading others to propose a multivariant prediction model represented by the formula 2.44C(age! 0.1)C(height!0.02)C(weight!0.016).52 A meticulous study recently suggested that none of the above-mentioned formulae seems able to predict the optimal size of endotracheal tube (uncuffed or cuffed) correctly. Among other reasons, the authors found a high product variability with regard to the outer diameter at a given internal diameter between different manufacturers and designs.53 In addition, the abovementioned calculations cannot be applied to children under the age of 2 years, and appropriately sized endotracheal tubes for infants and newborns must be chosen according to specified suggestions from the literature (see Table 2). Airway resistance Table 2. Recommendations for endotracheal tube size and positioning in infants and children.

Age

Internal diameter (mm)a

Gums/distance between incisors and mid-trachea (cm)b

Distance between nostril and mid-trachea (cm)c

Premature Newborn 3–9 months 9–18 months 1.5–3 years 4–5 years 6–7 years 8–10 years 11–13 years 14–16 years

2.0–3.0 3.0–3.5 3.5–4.0 4.0–4.5 4.5–5.0 5.0–5.5 5.5–6.0 6.0–6.5 (cuffed; 1.0)d 6.0–7.0 (cuffed; 1.0)d 7.0–7.5 (cuffed; 1.0)d

6–8 9–10 11–12 12–13 12–14 14–16 16–18 17–19 18–21 20–22

7–9 10–11 11–13 14–15 16–17 18–19 19–20 21–23 22–25 24–25

However, the appropriate endotracheal tube size for the individual child will vary according to age, height, weight, specific anatomical variations and ventilatory requirements; for most clinical situations, an air leak of 15–30 cmH2O is recommended. Modified from Finucane and Santora (2003, Principles of Airway Management 3rd edition, New York, Berlin: Springer, p. 395) with permission. Suggestions according to the formulae in children O2 years of age: a Uncuffed endotracheal tube, internal diameter (ID) in mmZ(age in years/4)C4. b Oral–tracheal distance in cmZ12C(age/2). c Naso–tracheal distance in cmZ15C(age/2). d Cuffed endotracheal tube, ID in mmZ(age in years/4)C3.

Airway management in infants and children 683

and flow characteristics can be improved significantly if the endotracheal tube is shortened, for example if a smaller-than-desired tube must be used.54 In the environment of anaesthesia, the size of the endotracheal tube appears to be less of a problem if children are ventilated using an anaesthesia machine. However, with the need for increasing the respiratory rate, the delivered tidal volume may decrease, thereby preventing a linear increase in minute volume. Interestingly, endotracheal tube size seems to matter more in children with normal lung compliance for the minute volume in relation to the peak inflation pressure, whereas in those with low compliance the lung appears to be the main determinant of delivered ventilation.55 Cuffed versus uncuffed endotracheal tubes Cuffed endotracheal tubes have not been advocated for use in children under the age of 8 years until recently. The key concern has always been that the inflated cuff poses an additional and unnecessary risk for both irritation and potentially ischaemia of the tracheal mucosa and the underlying soft tissue, with the same dangerous and possibly devastating consequences as described above for snug-fitting uncuffed endotracheal tubes. Some of these effects may in fact be related to the apparent poor design of most currently available cuffed endotracheal tubes, as recently demonstrated.53 Clinicians have also argued that the uncuffed endotracheal tube provides a larger inner diameter for a given outer dimension, thereby reducing resistance while improving laminar flow characteristics (see above), allowing a larger range to adapt to the respiratory needs, especially in the young child and infant. On the contrary, cuffed endotracheal tubes have been proposed by others to be advantageous even in small children for a number of reasons—e.g. to reduce the number of intubation attempts—because a potential leak due to a smaller (than for age) tube can be accommodated by the inflation of the cuff to achieve an appropriate airway seal. Additional valid reasons may be the reduction of anaesthetic gas contamination in the work environment, the option of providing low or minimal-flow anaesthesia or high-pressure ventilation and respective monitoring in, e.g. newborns with non-compliant lungs, and the reduction in risk for perioperative tracheal aspiration. Scientific proof, however, is lacking for all of the above (for review see reference 35). Recent studies have shown that the use of cuffed tubes is not associated with a higher incidence of respiratory complications in young children49,56,57 or infants.58 Despite these results, cuffed endotracheal tubes are not widely accepted among clinicians in different countries, and are in fact discouraged by several specialist groups in Europe.35,59,60 If cuffed endotracheal tubes are used in young children or infants, the cuff pressure should be monitored continuously, especially if nitrous oxide is used.60,61 Whether an air leak at, e.g. 20–25 cmH2O may be a sufficient substitute needs to be determined in future studies.62 A recently introduced paediatric tracheal tube with a so-called high-volume, low-pressure polyurethane cuff seems to be promising and may prompt a re-evaluation of current recommendations for the use of cuffed endotracheal tubes in children and infants.63 Placement of an endotracheal tube without muscle relaxants Endotracheal intubation can be achieved in children without muscle relaxant if desired. A recent multicentre survey64 showed good intubation conditions with inhalational sevoflurane (end-tidal concentration 5.9G1.5 vol%) in 97% of the children compared with 71% with intravenous propofol (5.8G4.2 mg/kg), which was slightly improved by the

684 A. M. Brambrink and U. Braun

concomitant use of opioids. Infants required higher sevoflurane concentrations for successful endotracheal intubation. The success rate at first attempt was also lower, and the peripheral oxygen saturation decreased more frequently than in older children. The authors found no difference in stridor on extubation between children intubated with cuffed (l.4%) or uncuffed (2.7%) tubes. These results indicate the need for a thorough evaluation of risks and benefits of muscle relaxation for intubation, especially in infants. Endotracheal intubation prior to transportation and in an out-of-hospital setting As of today it still is undetermined whether, among other patient groups, children benefit from endotracheal intubation in the field.65 A retrospective study documented an improved survival rate of children with severe blunt head traumas who received endotracheal intubation by emergency physicians at the scene;66 however, a large and widely recognized prospective study (830 consecutive patients, age 12 years or younger, all emergencies requiring ventilation) revealed that endotracheal intubation performed by paramedics in the field showed no effect on survival and neurological outcome compared with bag-valve-mask ventilation.67 With regard to possible complications, the authors conclude that the common practice of paramedics intubating children is questionable. Children in hospitals who need endotracheal intubation prior to transport may also be at risk; a prospective study of airway management in 250 children before transport to an intensive care unit found that anticholinergic agents were given infrequently, some patients received only neuromuscular blocking agents without sedation, and inappropriately sized endotracheal tubes were used.68 The increased necessity for qualified out-of-hospital care in children requires immediate efforts to analyse risks and benefits as well as potential means for improvement of airway management in children and infants either in the field or during transport. Practice points † endotracheal intubation is considered the gold standard to protect the airway in the critically ill child † children with upper respiratory tract infections carry an increased risk for respiratory complications with endotracheal intubation; however, anaesthesia can be considered safe when performed by an experienced anaesthesiologist † the resistance to airflow caused by the endotracheal tube is inversely proportional to the fourth power of its radius and directly proportional to its length, i.e. the narrower and longer the tube, the larger the flow resistance † tight-fitting endotracheal tubes may result in mucosal oedema; the younger the child, the smaller the degree of subglottic oedema necessary to cause critical airway obstruction † most widely accepted formula to determine the correct size of an uncuffed endotracheal tube relates to the age of the child: inner diameter in mmZ(16Cage in years)/4 † only recently, cuffed endotracheal tubes have been advocated for the use in children under the age of 8 years; they should only be used in this age group if the cuff pressure is monitored continuously † if desired, endotracheal intubation can be achieved in children without muscle relaxant

Airway management in infants and children 685

Research agenda † to identify and validate appropriate screening systems to predict a difficult airway in young children and infants † to determine whether children benefit from endotracheal intubation during emergency trauma care in the field † to determine whether critically ill children benefit from endotracheal intubation for interhospital transfer

TRACHEAL INTUBATION OF INFANTS AND CHILDREN USING FIBRE-ENDOSCOPES If conventional laryngoscopy does not allow for sufficient viewing of laryngeal structures, alternative techniques are necessary. This may include the application of different laryngoscope blades69,70, modified laryngoscopes (e.g. McCoy71, Bullard72), and the use of flexible or rigid fibrescopes. In several institutions, fibre-optic intubation of the trachea in children and infants with a difficult airway is performed under conscious sedation and maintenance of spontaneous ventilation.35,73 This procedure provides continuous oxygenation during tube placement, even if the procedure is more difficult than expected and requires additional manoeuvres or a second, more experienced operator to be successful. The regimen includes appropriate doses of benzodiazepines, ketamine, opioids or propofol according to the preference of the responsible physician, always sufficient topical anaesthesia of the mouth/ nose, pharynx, larynx and trachea using, e.g. 1–2% lidocaine (maximum 4.5 mg/kg topically, allowing 1–2 minutes to act) or similar techniques74, as well as appropriate monitoring and continuous oxygen insufflation (e.g. via the endoscope). Alternatively, tracheal intubation can be achieved after induction of general anaesthesia either intravenously or by inhalation.75 As a general rule, and similarly to adult patients, the operator needs to be fully confident that the child can be ventilated using a face mask or an appropriate supraglottic airway device (e.g. LMA, plan B) if endoscopic intubation of the trachea is intended under general anaesthesia. Several reports have been recently published about the use of an LMA as a conduit for successful endoscopic intubation of the trachea under general anaesthesia in this age group76–79, which appears to be an excellent choice for children with precisely documented mild to moderate airway abnormalities or limitations for conventional laryngoscopy (e.g. spine injury or facial burns). Flexible endoscopes for paediatric endotracheal intubation Appropriately sized instruments are available from different suppliers: e.g. Olympus, Pentax, Karl Storz (Table 3). Problems may occur in newborns and infants requiring endotracheal tubes size 3.0 or lower. In these patients, very small (‘ultra-thin’) flexible fibrescopes have to be used, but only one of the above-mentioned fibrescopes (Karl Storz, 2.8 mm outer diameter) provides a working channel for the application of topical anaesthesia, continuous oxygen flow or suction. The outer surface of this instrument has recently been redesigned (sandblasted) and fits a 3.0 tube for over-the-scope endotracheal intubation. However, even with the availability of this instrument, the placement of smaller tubes—e.g. 2.5 mm ID—still remains a challenge. For this situation, a ‘two-different-sizes bronchoscope technique’ has

686 A. M. Brambrink and U. Braun

Table 3. Flexible fibrescopes for endotracheal intubation in infants and children. Endoscope (outer diameter in mm)

Instrument channel (inner diameter in mm)

Olympus (Olympus Europa GmbH, Hamburg, Germany)

4.0 3.6 2.2

1.5 1.2 None

Pentax (Pentax Medical Company, Montvale, NJ, USA)

3.1 2.4

1.2 None

Karl Storz (Karl Storz GmbH & Co. KG, Tuttlingen, Germany)

3.7 2.8

1.5 1.2

Manufacturer

been suggested80, described first by Kleemann et al81: a small bronchoscope (e.g. the Olympus 2.2 mm outer diameter) carries the endotracheal tube (e.g. 2.5 mm inner diameter), while the biopsy channel of a second (larger) one allows the application of topical anaesthesia and the continuous flow of oxygen during most of the procedure. Rigid fibrescopes for endotracheal intubation in infants and children Rigid or semi-rigid bronchoscopes are even less frequently used in infants and children than in adults. Most available equipment has been designed for use in adult patients: e.g. Bonfils82, Upsher Scope, and Wu Scope (the last two are virtually laryngoscope/ bronchoscope hybrids). Only a few such devices have been used in small children: e.g. the Shikani Optical Stylet.83 The experienced operator has an improved view of the airway structures, and endotracheal intubation is facilitated—especially in patients with a difficult anatomy. Rigid bronchoscopes are generally less expensive to acquire and maintain than flexible endoscopes, and some clinicians consider them easier to use than the latter after having achieved sufficient training with the particular rigid technique.84 Others have introduced two different semi-flexible miniature scopes (outer diameter 2.0 mm) specially designed for use in infants and small children.85,86 Special adapters allow for the adjustment of the various lengths of paediatric endotracheal tubes, as well as continuous oxygen administration alongside the scope through the lumen of the endotracheal tube. The first systematic clinical evaluation of one of the new devices showed a significantly better visualization of the larynx and vocal cords and excellent success with tracheal intubation.87 Endotracheal intubation using a rigid fibrescope is typically considered to require general anaesthesia by either intravenous or inhalation technique. This would exclude the application of these devices in children with a difficult airway which has not previously been fully evaluated and may present an airway obstacle to a straight tube placement, or which may pose a risk for unexpected anatomical changes since the last procedure. In these cases fibre-optic intubation using a flexible endoscope under adequate sedation appears to be safer for the child. Video-assisted systems for endoscopic airway management in children and infants In our opinion, video-assisted systems for endotracheal intubation will gain more popularity in paediatric anaesthesia due to the large image on the TV screen which can be

Airway management in infants and children 687

seen with both eyes, and without having to adapt to the operator’s vision.88,89 Additionally, because assistance during the intubation procedure is essential (e.g. pressure on the larynx, chin lift, advancement of the endotracheal tube providing anaesthesia), these tasks can be carried out much more efficiently using a video display. Finally, video-assisted intubation appears to be an excellent teaching tool, as the attending anaesthesiologist can demonstrate the procedure to the resident or student as well as precisely observe and correct the procedure when performed by the resident, as has recently been proved by a systematic analysis.90 Some novel devices seem to be particularly promising. Two different semi-flexible miniature video neonatal intubating scopes (outer diameter 2.0 mm) have been introduced, both of which are equipped with integrated DCI TV cameras and special adapters to adjust the various lengths of endotracheal tubes and allow for simultaneous oxygen administration alongside the scope through the tube.85,86 One of these scopes has been evaluated in a larger multicentre trial.87 Another recently developed video laryngoscope (Acutronic Medical Systems AG, Hirzel, Switzerland) was used to intubate the trachea in patients with Pierre Robin sequence.91 Integration of very small TV cameras into the handle of flexible fibrescopes results in an always-ready-to-use system for video-guided fibre-optic intubation of the trachea in infants and children.92,93 Finally, the concept of a special airway management cart appears to facilitate manipulation and observation during fibreoptic intubation: the TV monitor is mounted on a swivel arm containing the camera control unit, light source and videotape recorder. This allows for the projection of the video image above the patient’s chest.85

Practice points † as in adults, fibre-optic tracheal intubation in children and infants can be achieved under conscious sedation and maintenance of spontaneous ventilation; alternatively, fibre-optic tube placement may be performed after induction of general anaesthesia if it is known that the child can be oxygenated using mask-bag ventilation † the LMA can be helpful as a conduit to guide endoscopic intubation † appropriately sized instruments are available from different suppliers; consider the ‘two-different-sizes bronchoscope technique’ if necessary † rigid bronchoscopes are less frequently used in young children; their use typically requires general anaesthesia prior to airway management † video-assisted systems for endotracheal intubation allow observation of the procedure with both eyes (video image and the ‘outside’ at the same time); they do not require vision adaptation, improve assistance during the procedure, and provide excellent teaching opportunities PATHOLOGICAL CONDITIONS Various craniofacial abnormalities arise from maldevelopment of the first and second visceral arches which form the facial bones and ears during the second month of gestation. These malformations include cleft lip and cleft palate, Treacher–Collins (synonym in Europe: Franceschetti), Goldenhar, Pierre Robin and Nager syndromes. Children with these malformations have normal intelligence.

688 A. M. Brambrink and U. Braun

Treacher–Collins syndrome is also called mandibulofacial dysostosis. It includes malformed external ear, malar and mandibular hypoplasia, anti-mongoloid slanting, palpebral fissures, coloboma of lower eyelid, and conductive hearing loss. Goldenhar syndrome (oculo-auriculo-vertebral dysplasia) shows facial asymmetry unique to this syndrome, microphthalmia, epibulbar lipodermoid, malformed external ear, conductive hearing loss, macrostomia and mandibular hypoplasia. Pierre Robin (PR) syndrome is rather named PR sequence today, because beside the typical features other malformations are combined with it in a variable way. The typical malformations are micrognathia with glossoptosis and cleft soft palate. The Nager syndrome is also called acrofacial dysostosis. It includes mandibular and velum hypoplasia and thumb dysplasia or aplasia. Eye and ear anomalies may be present. Depending on the severity of the anatomical changes, noisy breathing, airway obstruction and feeding problems may arise. Some malformations are so severe that the children die at an early age. Mandibular hypoplasia is prevalent in many of the aforementioned malformations. It can contribute to airway obstruction and feeding problems, as in the Nager syndrome.94 Mandibular hypoplasia is a frequent feature of craniofacial malformations. It may be treated with mandibular distraction osteogenesis. With this rather non-invasive approach the mandible can grow after double osteotomy and fixation of a bidirectional distractor.95 Severe symptoms of airway obstruction may be relieved in infants and small children. Mucopolysaccharidosis (MPS) is caused by a specific genetic enzyme defect and has distinct clinical features, a predictable prognosis, increased urinary mucopolysaccharide

Figure 1. Franceschetti syndrome.

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excretion, and variable systemic manifestations. Among these a typical facial appearance, corneal opacity, skeletal dysplasia, mental deficiency, hepatosplenomegaly and severe airway problems may be observed.96,97 Today there are seven subtypes of the disease, MPS I–VII, number VI with types A and B. The Hurler description is type I. Patients with this disease usually do not reach the age of 10 years. Noma (cancrum oris) is an acquired infectious disease associated with poverty and malnutrition in sub-Saharan African and South American regions.98 It is an orofacial gangrene arising as the result of a rapidly spreading opportunistic infection caused by the normal oral flora. Most children die in the acute phase; only around 10% survive. They are left with facial and bony destruction which leaves major scars, open nasal and oral cavities and trismus. At that stage surgery may improve the patient situation with reconstructive plastic and maxillofacial interventions. Treatment of the acute phase with infusions and antibiotics is successful provided that the children do not reach the hospital too late. Some years ago we were faced with an 11-year-old very small boy with Franceschetti syndrome and phocomelia who could not be intubated for dental treatment (Figure 1). After providing a flexible endoscope with a diameter of 3.6 mm, we put the patient to sleep with spontaneous ventilation under halothane. The problem was to keep the anaesthetic level and spontaneous breathing stable. It was difficult to visualize the larynx because of a very narrow pharynx and the gravity effect in the supine position. Intubation was successful after 40 minutes, and surgery and anaesthesia were uneventful. This was a key experience for the management of

Figure 2. Goldenhar syndrome.

690 A. M. Brambrink and U. Braun

the difficult airway and made us follow that clinical path. We preferred inhalational anaesthesia with halothane or sevoflurane and spontaneous ventilation if fibre-optic intubation was indicated. It is essential to reach a deep level of anaesthesia and to keep spontaneous ventilation well preserved. We also used ketamine and benzodiazepines, but our experience was that it is not possible to reach a deeper level of anaesthesia with less protective reflex activity and to avoid laryngospasm. We have applied LMA successfully in Goldenhar syndrome99, Pierre Robin sequence and Nager syndrome when intubation was not indicated (Figures 2–4). This is confirmed by an overview of the literature19 and is also applicable to the Treacher– Collins (Franceschetti) syndrome. We performed a fibre-optic intubation via the LMA if there was an indication for it. In infants and small children, only the standard version of the LMA (classic) could be applied. The flexible LMA is very useful for anaesthesia, but not for fibre-optic intubation. Today the Proseal LMA may be even more appropriate for anaesthesia in this patient group. Mucopolysaccharidosis (MPS) warrants a different airway approach from that in the craniofacial malformations. We have anaesthetized six male patients with this syndrome between 3 and 42 years of age (type I, Figure 5, type II, two cases, type IV, and type VI, two cases). The severity of the course of the disease depends upon the type of enzyme defect.

Figure 3. Pierre Robin sequence.

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Figure 4. Nager syndrome with distractor.

Type I (Hurler) is the most symptomatic MPS class. All patients had to be intubated for minor or moderate surgical interventions. The oldest patient with a type IV disease could be intubated conventionally with ease. All others needed a fibre-optic intubation via the LMA. In one we performed an awake procedure after topical anaesthesia in the sitting position (14 years of age); in all others the LMA and the tracheal tube were positioned under intravenous or inhalational anaesthesia. Face-mask ventilation was possible when it was needed. Selection of LMA size was difficult. Placement of the LMA may or may not be successful. Change in positioning of head and neck and tongue manipulation may be necessary. There are extensive anatomical variations around the larynx. One of the authors (UB) took part in a team effort to treat 37 noma patients in Nigeria in the year 2000, many of which were children (Figure 6). In these patients the face mask and the LMA cannot be applied, and a fibre-optic intubation technique has to be used. The tolerance for the awake fibre-optic was better than that in Europe. The patients cooperated from the age of 12 years and above; younger patients received halothane. Spontaneous ventilation was preserved. There was a 100% success rate with fibre-optic intubation, in one case after a second attempt. From our experience we can summarize that tracheal intubation is difficult in all of the mentioned patient groups. The laryngeal mask is a very effective airway tool for craniofacial malformations, much less so for the mucopolysaccharidoses, and is not applicable in noma patients. The face mask may or may not work in craniofacial disorders and MPS and is not effective for the noma group. It is important to preserve

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Figure 5. Mucopolysaccharidosis (MPS) type Hurler.

consciousness and/or spontaneous ventilation if very difficult airway conditions are met. The decision to anaesthetize should be taken only if face mask or LMA ventilation can be provided safely. If these conditions are not known, fibre-optic intubation under spontaneous ventilation is the only secure approach. Practice points † several craniofacial abnormalities occur early during pregnancy (2nd gestational month) † others are acquired during childhood and may result from various causes, e.g. metabolic or infectious diseases

SUMMARY Airway management in children and infants, especially in those with a difficult airway, presents a major challenge for every anaesthesiologist, paediatrician, paediatric

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Figure 6. Noma: (a) preoperative, and (b) postoperative.

intensivist and emergency physician. The most important differences, as compared to adult airway management, result from the specific aspects of paediatric anatomy and physiology, which are more important to consider the younger the child is. A number of inherited and acquired pathological syndromes have significant impact on the airway management in this age group. During past years several new devices have been introduced into clinical practice, intended to improve airway management in this age group. Important new studies have gathered evidence about risks and benefits of certain confounding variables for airway problems and specific techniques for solving them. Several risk factors for airway-related problems during anaesthesia in children having a ‘cold’ have been identified, and the use of propofol in combination with the LMA is suggested if anaesthesia cannot be postponed in children with a recent upper airway infection. The use of cuffed endotracheal tubes appears to be advantageous in certain clinical situations, and may be safe in infants if the appropriate tube size is carefully determined and continuous monitoring of the cuff pressure is performed to avoid post-intubation tracheal stenosis. Promising novel video-assisted systems comprising appropriately sized and redesigned fibre-optic endoscopes have been introduced for the management of the difficult airway in small children, infants and even premature newborns. Today, the laryngeal mask airway is a well-accepted extra-tracheal airway device in paediatric anaesthesia, and the flexible LMA allows for its use during ENT and dental surgery procedures. However, LMA-associated partial obstruction of the airway in infants requires great caution when these devices are used in this age group. The recently introduced Proseal LMA for children may allow higher airway pressures and improved protection from gastric inflation, e.g. in paediatric ambulatory anaesthesia. The LMA may also serve well to guide the endoscope during fibre-optic intubation in children and infants. Prediction of the unexpected difficult airway in infants and children remains really difficult, as the respective screening systems have been developed in adults

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and are, for a variety of reasons, not applicable to young children and infants. A thorough determination of the individual risk of developing airway complications, as well as continuous attention to airway patency during the procedure, are prerequisites for reducing airway-related morbidity and mortality in children and infants during anaesthesia. Appropriate preparation of the available equipment and frequent training in management algorithms for all personnel involved appear to be very important.

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