A Child With a Difficult Airway ASA 2014

Refresher Course Lectures Anesthesiology 2014 © American Society of Anesthesiologists. All rights reserved. Note: This publication contains material copyrighted by others. Individual refresher course lectures are reprinted by ASA with permission. Reprinting or using individual refresher course lectures contained herein is strictly prohibited without permission from the authors/copyright holders.

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A Child with a Difficult Airway: Succeed with the Tricks of the Trade

Paul Reynolds, M.D. Ann Arbor, Michigan

Introduction Pediatric airway management can be challenging. Even though difficult airways in children are a relatively

rare phenomenon compared to adults, children with normal airways can pose problems to clinicians unaccustomed to managing small children. A study of closed anesthesia malpractice claims suggests a higher incidence of cardiac arrest due to loss of airways in normal children, especially less than 1 year of age (1). This may be due to the anesthesia care providers unfamiliarity with anatomical differences between the adult and pediatric airway, as well as the physiological and metabolic differences.

Differences between the adult and pediatric airways

Anatomical differences

Successful management in children, especially under 1 year of age, requires the anesthetist to understand both anatomical and physiological differences between adults and children. A child’s airway typically becomes anatomically adult after 6 to 8 years of age. For maximum differentiation, I compare a neonate’s airway (children under 1 month of age), to an adult. Neonates are obligate nasal breathers. Nasal obstruction for prolonged periods of time (e.g. choanal atresia) can be fatal. Neonates also have much more narrow nares compared to adults. This can make passage of nasotracheal tube more difficult. The nasal opening may be smaller than the laryngeal opening, leading to a large airway leak unless a cuffed nasotracheal tube is used. Unlike an adult, the neonates tongue rests at the roof of the mouth during quiet respiration. The tongue is also large in relation to the mouth, making both mask ventilation and oral intubation more difficult. The neonates head is large in relation to their body. During mask ventilation or laryngoscopy, the goal is to align the oral, tracheal and pharyngeal axis (sniffing position). In an adult, this is accomplished by placing a pillow behind the head. However, in the neonate or infant, because of relatively large head, a pillow should be placed behind the shoulders. The larynx is higher in the neck of a neonate (C 3-4) when compared to an adult (C 4-5). This, in combination with a shorter neonatal neck can lead to more difficult laryngeal visualization during direct laryngoscopy. In addition, the small mouth of a neonate requires the use of a straight laryngoscope blade to visualize the laryngeal opening. The epiglottis in adults is broad, with its axis parallel to the trachea, while a neonate’s epiglottis is long, narrow and floppy, angulated away from the axis of the trachea. During laryngoscopy, the tip of the neonate’s epiglottis is lifted by the laryngoscope for glottic visualization. Adult’s vocal folds are perpendicular to the axis of the trachea, while the vocal folds of a neonate have a lower anterior attachment to the glottis than posteriorly. This can sometimes lead to difficulty in passing the endotracheal tube through the neonate’s glottis.

It has been often stated the narrowest portion of the neonatal airway is at the level of the cricoid ring, as compared to the adult, where the laryngeal opening is the narrowest. Thus, the immature larynx has a funnel shape, compared to the cylindrical shape of the adult larynx. This is part of the rationale for the use of uncuffed endotracheal tubes in children less than 6 years of age. If the narrowest portion of the pediatric airway is the cricoid ring, being perfectly circular, an uncuffed tube is ideal. Conversely, the narrowest portion of the adult airway, at the level of the vocal folds, an irregular shape, requires a cuffed endotracheal tube. Evidence of laryngeal shapes in children was based on an article in Anesthesiology published in 1951 by Eckenhoff (2), not by a study of his own, but an examination of 15 plaster casts made from cadaveric larynxes preserved from children, ages 4 months to 14 years, who died in 1897 (3). A study, published in Anesthesia & Analgesia by Dalal et.al (4). examined 135 anesthetized children, aged 6 months to 13 years of age, using video bronchoscopy to measure laryngeal dimensions. The authors concluded “the glottis, rather than the cricoid, was the narrowest potion of the pediatric airway”. Thus, the shape of the pediatric airway was cylindrical, similar to the adult shape. This study leads to the discussion of cuffed vs. uncuffed endotracheal tubes in children. The advantages of an uncuffed endotracheal tube include a larger internal diameter, lower resistance to airflow, and avoidance of trauma to the subglottic region. Advantages


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of cuffed endotracheal tubes include lower fresh gas flow, reduced air pollution, less inhalational agent used, reduced risk of aspiration, avoids multiple intubations, and improved ventilation and end-tidal CO2 monitoring (5). In a review of the current literature, Taylor et.al. (6) conclude there is strong evidence to support the use of cuffed endotracheal tubes in children.

Physiologic differences

Neonatal oxygen consumption, as well as metabolic rate, is much higher in than in adults. To compensate, neonatal cardiac index as well as minute ventilation are 2 to 3 times that of adult. Functional residual capacity (FRC), is the volume of air in the lungs at the end of expiration, and is dependent on size of patient, the elasticity of the chest wall, and inward recoil of the lungs. Neonates are smaller and have more compliant chest walls. Under anesthesia, neonatal FRC approaches closing volumes, causing more atelectasis in a shorter period of time. These differences in physiology translate to shorter periods of apnea tolerated in neonates before oxygen desaturation occurs. In addition, because of the inability of children to cooperate with preoxygenation, desaturation with rapid sequence induction can occur much quicker. The laryngoscopist not skilled in pediatric airway management has an even shorter time to secure an airway.

What makes a pediatric airway difficult?

There are many causes for difficult airways in pediatric patients. Congenital abnormalities, such as Pierre Robin syndrome, Goldenhar’s and Treacher Collins Syndrome are all examples of syndromes associated with difficult airways. Facial or airway trauma, burns, surgical scarring or radiation therapy can all cause difficult airways in children. Inflammatory processes such as infections or rheumatoid arthritis can predispose to airway problems. Other diseases, including neoplasms or metabolic diseases (Mucopolysaccharidosis) can be challenging. Obesity may also contribute to difficulty masking children. Nafiu et.al. found a positive correlation between large neck circumference in children and upper airway obstruction both in the operating room and recovery room (7). The goal of direct laryngoscopy is to allow a line of site from the teeth or alveolar ridge to the laryngeal opening. The blade of the laryngoscope displaces the soft tissue in the mandible into a potential space encompassed (and potentially restricted) by an incomplete bony ring bound posteriorly by the hyoid bone, laterally by the rami of the mandible, and anteriorly by the mentum of the mandible. Any alteration in the shape or size of these bony structures results in a decrease in this space that the laryngoscope can displace the soft tissues, (e.g.; Pierre Robin, Treacher Collins). Alternatively, an increased amount of soft tissue in the area of the tongue will have the same effect, (e.g.; macroglossia, cystic hygromas).

Diagnosis of a difficult airway

A careful history, and detailed airway examination should be obtained prior to anesthetizing a child with a difficult airway. One should suspect a difficult airway in a child if any of the following history is elicited: noisy breathing or stridor, variable airway related to position, problems with feeding, leading to severe coughing and cyanosis. Additionally, an infant or child who has airway problems associated with either URI or feeding will probably have the same problems when given sedatives or narcotics, or after induction of anesthesia. Extra precaution should be taken if the child has a history of difficult intubation in the past. Every attempt should be made to obtain previous anesthetic records. The physical examination of a child with a suspected difficult airway should begin with a careful inspection of the face, looking for asymmetry, dysmorphism, or any other unusual features. The ears, mandible and the larynx are all formed during the 9th week of gestation, from the same group of branchial arches. Abnormal ears shapes may be associated with airway malformations. Nasal patency should be checked bilaterally. The mouth opening should be assessed, as well as the size of the tongue, and Mallampatti score noted. Mandibular size and mobility should be assessed, as well as flexion, extension and rotation of the neck. Ideally, diagnostic studies can be performed prior to induction of anesthesia. Simple x-rays of the head and airways, as well as CT scans can be helpful for determining boney abnormalities. MRI’s are useful for imaging soft tissues; however, the duration of the exam usually requires sedation or anesthesia in small or uncooperative children.

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Management of a difficult airway

If a child requires intubation, and has a known difficult airway, a well thought out plan, with alternative measures for intubation should be planned. ASA Practice guidelines for management of the difficult airway (8) note the pediatric patient may limit options for airway management (awake fiberoptic intubation), necessitating deep sedation or, more commonly, general anesthesia for securing the child’s airway. A survey of pediatric Anesthesiologists in Canada (9) found inhalational anesthesia the preferred technique for pediatric patients with difficult airways. If general anesthesia is chosen for securing the airway, one option is to induce the child with sevoflurane, and 100% oxygen. After intravenous access is secured, oxymetazoline (Afrin nasal spray) 0.05% solution, is sprayed into both nares to prevent epistaxis. A nasal airway with an endotracheal tube connector is placed, and high concentrations of sevoflurane and oxygen are insufflated into the child’s hypo pharynx via this connection. A fiberoptic scope, fitted with an appropriate sized endotracheal tube, is then introduced either into the opposite nares, or the oropharynx to facilitate tracheal intubation. If the scope has a suction channel, either suction or a second oxygen source is attached to the channel. It is quite helpful if an assistant gently pulls the patients tongue forward with gauze or a ringed forceps to open the pharyngeal space, and enhance visualization. A small dose of 1 % lidocaine (less than 5 mg/kg) may be injected into the suction port of the fiberscope after it has been positioned over the laryngeal inlet to prevent cough when inserting the endotracheal tube.

Airway devices

A number of supraglotic airways can be used to secure the airways of children with difficult airways, or facilitate intubation of the airway. Laryngeal Mask Airways (LMA Intavent Orthofix) were invented By Dr. Archie Brain and first used in humans in 1981. LMA’s are often used to facilitate tracheal intubation in children with difficult airways in conjunction with fiberoptic scopes (10). Since the introduction of the LMA, several other supraglotic devices have been introduced and have been used in children with both normal and difficult airways (11). The Proseal LMA (PLMA Intavent Orthofix) is a second generation LMA with an esophageal drain and an integrated bite block, comes in both pediatric and neonatal sizes.

A number of airway devices have been used in children to facilitate intubation and are useful as an alternative to direct laryngoscopy or fiberoptic intubation in children with difficult airways. A review article by Holm Knudsen (12), compared four commercially available devices current used in the pediatric population. The Airtraq (Prodol Meditec) is a single use device which uses an eye piece or light weight video monitor instead of line of site between the user and laryngeal opening (as in the case of laryngoscopy). Pediatric and neonatal sizes are available. The Glidescope Video Laryngoscope (Verathon) works on the same principal as the Airtraq, (indirect laryngoscopy) but uses a video monitor, had disposable blades, and comes in pediatric and neonatal sizes. The Stortz DCI Video Laryngoscope (Karl Stortz) can be used for both direct and indirect laryngoscopy has 2 Miller like blades, sizes 0 and 1. I personally have found this device extremely helpful while intubating neonates with Pierre Robin syndrome. The Trueview PCD Infant (Truphatek) is a reusable indirect laryngoscope with an eyepiece (adaptable to a videocamera) with a wide magnified laryngeal view. It also has an adapter for insufflation of oxygen. The authors conclude fiberoptic intubation is still the gold standard for pediatric difficult airways. The Shikani Optical Stylet (SOS, Clarus Medical) has also been used to intubate children with difficult airways. Shukry et.al. describe 3 children with difficult airways, who were successfully intubated with this device(13). The SOS combines the benefits of a lightwand and a rigid bronchoscope.

Unexpected difficult airways

Although rare, unexpected difficult intubation in children can be devastating. As mentioned earlier, a study of closed anesthesia malpractice claims suggests a higher incidence of cardiac arrest due to loss of airways in normal children, especially less than 1 year of age (1). Weiss et.al. proposed an simple algorithm based on the adult Difficult Airway Society protocol, adapted for the pediatric population (14). In addition to the algorithm, the authors recommend each department have a pediatric airway trolley/bag, where specialized equipment is available to manage airway emergencies in children. Rarely, a patient may deteriorate to a point where the clinician may not be


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able to ventilate or secure an airway (cannot intubate/cannot ventilate). In this instance surgical airway must be secured in rapid fashion. Cote et.al. reviewed a number of techniques and devices designed for the anesthesiologists use in children in this scenario. They concluded the appropriate sized equipment should be utilized, and that cricothyrotomy in a neonate or small infant is extremely dangerous. Intravenous catheter devices are recommended in infants, as anesthesiologists are much more comfortable with IV catheters than scalpels (15).

References

1. Morray JP, Geiduschek JM, Caplan RA, Posner KL, Gild WM, Cheney FW, A Comparison of Pediatricand Adult Anesthesia Closed Malpractice Claims, Anesthesiology, 1993;78:461-467.

2. Eckenhoff JE, Some Anatomic Considerations of the Infant Larynx Influencing Endotracheal Anesthesia,Anesthesiology The Journal of the American Society of Anesthesiologists, Inc, 1951;12(4):401-409.

3. Motoyama EK, The Shape of the Pediatric Larynx: Cylindrical or Funnel Shaped?, Anesthesia &Analgesia, 2009;108(5):1379-1381.

4. Dalal PG, Murray D, Messner AH, Feng A, McAllister J, Molter D, Pediatric Laryngeal Dimensions: AnAge-Based Analysis, Pediatric Anesthesiology 2009;108(5):1475-1479.

5. Bhardwaj N, Review Article: Pediatric cuffed endotracheal tubes, Journal of Anaesthesiology ClinicalPharmacology, 2013;29(1):13-18.

6. Taylor C, Subaiya L, Corsino D, Pediatric Cuffed Endotracheal Tubes: An Evolution of Care, The OchsnerJournal, 2011;11:52-56.

7. Nafiu OO, Burke CC, Gupta R, Christensen R, Reynolds PI, Malviya S, Association of NeckCircumference with Perioperative Adverse Respiratory Events in Children, Pediatrics, 2011;127(5).

8. American Society of Anesthesiologists: Practice guidelines for management of the difficult airway: AnUpdated report by the American Society of Anesthesiologists Task Force on Management of the DifficultAirway, 2013;C118(2):1-20.

9. Brooks P, Ree R, Rosen D, Amsermino M, Canadian pediatric anesthesiologists prefer inhalationalanesthesia to manage difficult airways: a survey, Obstetrical and Pediatric Anesthesia, Can J Anesth,2005;52(3):285-290.

10. Reynolds PI, O’Kelly SW, Fiberoptic Intubation and the Laryngeal Mask Airway, Anesthesiology,1993,79:1144.

11. White MC, Cook TM, Stoddart PA, Review article: A critique of elective pediatric supraglottic airwaydevices, Pediatric Anesthesia, 2009;19(1):55-65.

12. Holm-Knudsen R, Review Article: The difficult pediatric airway – a review of new devices for indirectlaryngoscopy in children younger than two years of age, Pedaitric Anesthesia, 2011;21:98-103.

13. Shukry M, Hanson RD, Koveleskie JR, Ramadhyani U, Case report: Management of the difficult pediatricairway with Shikani Optical SyletTM, Pedaitric Anesthesia, 2005;15:342-345.

14. Weiss M, Engelhardt T, Proposal for the management of the unexpect4ed difficult pediatric airway,Pediatric Anesthesia 2010;20:454-464.

15. Cote CJ, Hartnick CJ, Review article: Pediatric traqnstracheal and cricothyrotomy airway devices foremergency use: which are appropriate for infants and children? Pediatric Anesthesia 2009;19(1):66-76.

Disclosure No financial relationships with commercial interest

A Child With a Difficult Airway ASA 2014

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