Chapter 13 Airway Management
1. What is the definition of difficult mask ventilation?
2. What is the incidence of difficult mask ventilation?
3. What is the definition of difficult tracheal intubation/laryngoscopy?
4. What is the incidence of difficult tracheal intubation/laryngoscopy?
Anatomy and physiology of the upper airway
6. How does resistance to airflow through the nasal passages compare to that through the mouth?
7. What nerves innervate the nasal mucosa?
8. What nerves innervate the hard and soft palate?
9. What nerve provides sensation to the anterior two thirds of the tongue?
10. What nerve innervates the posterior third of the tongue, the soft palate, and the oropharynx?
11. What are the three components of the pharynx?
12. What nerves innervate the pharynx?
13. Complete the following table: (223, Table 16-1, Motor and Sensory Innervation of Larynx)
| Nerve | Sensory | Motor |
|---|---|---|
| Superior laryngeal, internal division |
||
| Superior laryngeal, external division |
||
| Recurrent laryngeal |
14. Where is the narrowest part of the adult airway?
15. What is special about the cricoid cartilage compared with the other tracheal cartilages?
Airway assessment
16. What is the purpose of the Mallampati classification system?
17. Describe the observer/patient position during Mallampati classification.
18. Describe the Mallampati classes.
19. What is the purpose of the Cormack and Lehane score?
20. Describe the Cormack and Lehane grades.
21. What is the purpose of the upper lip bite test (ULBT)?
22. Describe the upper lip bite test (ULBT) classes.
23. What three axes must be aligned to obtain a line of vision during direct laryngoscopy? How is this accomplished? What is this final position called?
24. What is the concern with a “short” thyromental distance?
25. What is the concern with a decreased submandibular compliance?
26. What position is associated with improved alignment of the three axes to obtain a line of vision during laryngoscopy in obese patients?
27. What maneuver facilitates identification of the cricoid cartilage in patients who do not have a prominent thyroid cartilage?
Airway management techniques
28. What is “preoxygenation” prior to the induction of anesthesia? What is its value?
29. How is preoxygenation accomplished?
30. Name ten independent variables that are associated with difficult facemask ventilation.
31. Why is it important to limit ventilation pressure to less than 20 cm H2O during facemask ventilation?
32. What are contraindications to nasal airway placement?
33. What are some indications for endotracheal intubation?
34. What is another name for cricoid pressure and how is it performed?
35. What is the purpose of cricoid pressure?
36. Describe the proper placement of the tip of a curved (Macintosh) laryngoscope blade versus that of a straight (Miller) laryngoscope blade for exposure of the glottic opening during laryngoscopy.
37. Describe the OELM and BURP maneuvers. What is their purpose?
38. How are endotracheal tubes sized?
39. Why are endotracheal tubes radiopaque and transparent?
40. Why are low-pressure, high-volume cuffs on endotracheal tubes preferred?
41. What are some serious complications attributable to endotracheal cuff pressures?
42. Name some stylets that can be used to facilitate endotracheal intubation.
43. What are some methods to confirm the correct placement of an endotracheal tube?
44. When is an awake fiberoptic endotracheal intubation most frequently chosen?
45. Why is fiberoptic endotracheal intubation recommended for patients with unstable cervical spines?
46. Why is fiberoptic endotracheal intubation recommended for patients who have sustained an injury to the upper airway from either blunt or penetrating trauma?
47. What is an absolute contraindication to fiberoptic endotracheal intubation?
48. What are some relative contraindications to fiberoptic endotracheal intubation?
49. What are some advantages and disadvantages of nasal fiberoptic endotracheal intubation?
50. Why should an antisialagogue be given before fiberoptic endotracheal intubation?
51. On what basis is the choice of sedation for an awake fiberoptic tracheal intubation made?
52. Describe preparation of the nose and nasopharynx for nasal fiberoptic tracheal intubation.
53. Describe preparation of the tongue and oropharynx for nasal or oral fiberoptic tracheal intubation.
54. Describe preparation of the larynx and trachea for nasal or oral fiberoptic tracheal intubation.
55. Why is lidocaine the preferred airway topical local anesthetic?
56. Name two blocks that can be performed to topicalize the larynx and trachea.
Flexible fiberoptic laryngoscopy
57. How can the risks of mucosal trauma or submucosal bleeding with nasal endotracheal intubation be minimized?
58. What advantages does inflation of the endotracheal tube cuff during advancement with the fiberoptic scope offer?
59. How is endotracheal tube depth verified during fiberoptic intubation?
60. What are possible causes of resistance when removing the fiberoptic bronchoscope?
61. What is the utility of oral intubating airways during oral fiberoptic endotracheal tracheal intubation?
62. Why is visualization more difficult during fiberoptic endotracheal tracheal intubation in an asleep patient?
63. Why is having a second person trained in anesthesia delivery present recommended for fiberoptic endotracheal tracheal intubation in an asleep patient?
Supraglottic airway devices
Tracheal extubation
76. Why is tracheal extubation during a light level of anesthesia dangerous?
77. What is laryngospasm? When is it most likely to occur?
78. How should laryngospasm be treated?
79. When is deep tracheal extubation contraindicated?
80. What are the steps of tracheal extubation?
81. What is the most common complication during direct laryngoscopy?
82. Describe endotracheal tube movement during head flexion and extension.
83. What are the two most serious complications after tracheal extubation?
84. What is the major complication of prolonged tracheal intubation?
Airway management in infants and children
85. What are some differences between the infant and the adult airway? At what age does the pediatric upper airway take on more adultlike characteristics?
86. Contrast the location of the larynx in an infant versus an adult. What effect does this have on the tongue?
87. Contrast the size of an infant’s tongue in proportion to the size of the mouth with that of an adult. What are the consequences of this?
88. Contrast an infant’s epiglottis with that of an adult.
89. What advantages do straight laryngoscopes offer over curved laryngoscopes when intubating an infant or small child?
90. What is the narrowest portion of an infant’s airway versus an adult airway?
91. What is the correct size of an uncuffed endotracheal tube in infants and children?
92. Can cuffed endotracheal tubes be safely used in infants and children? What if nitrous oxide is used during the anesthetic?
93. What are the dangers of an endotracheal tube that is too large for infants and children?
94. Contrast proper head and neck positioning of an adult with that of an infant during direct laryngoscopy.
95. What is different about an infant’s nares compared to an adult’s? Why is this important?
96. Why is a history of snoring important in infants and children?
97. Why is premedication useful in pediatric anesthesia? At what age does this become important?
98. What is the dose of oral midazolam for infants or children? What is the maximum oral dose? What if the child is uncooperative with taking oral midazolam?
99. Describe an inhaled induction in a child. When should the nitrous oxide be discontinued?
100. Describe maneuvers to overcome airway obstruction during mask induction in infants and children.
101. What determines the appropriate size of an LMA for use in infants and children?
102. What is the LMA Flexible? What advantages does it offer?
103. What advantage does the Air-Q intubating laryngeal airway (ILA) have over an LMA?
104. What formula is often used to estimate the appropriate-sized endotracheal tubes for infants and children?
105. Is the formula used to estimate the appropriate-sized endotracheal tube for infants and children applicable for cuffed or uncuffed endotracheal tubes?
106. How is the formula used to estimate the appropriate-sized endotracheal tubes for infants and children adapted for cuffed endotracheal tubes?
107. What three advantages do Microcuff endotracheal tubes have over conventional pediatric cuffed endotracheal tubes?
108. Are stylets useful in intubating infants and children?
109. What is the disadvantage of a straight laryngoscope blade compared to a curved blade?
110. Describe the most useful sizes of laryngoscope blades according to age.
111. What is the most important first step when an unexpected difficult airway occurs in pediatric patients?
112. Why should repeated attempts at direct laryngoscopy be avoided? What should be done instead?
113. Is an awake fiberoptic endotracheal intubation usually an option in managing an expected pediatric difficult airway?
114. What personnel and equipment should be in the operating room before induction of anesthesia in a pediatric patient with an expected difficult airway?
115. What airway devices are available in smaller sizes to facilitate intubation of a child with a difficult airway?
116. Why is tracheal extubation in infants and children riskier than that of adults?
117. When does postextubation croup most commonly occur? Why is this important?
118. What are the clinical manifestations of postextubation croup?
119. How is postextubation croup treated?
120. Why is obstructive sleep apnea especially important in infants and children?
121. How should opiate therapy be managed in an infant or child with obstructive sleep apnea?
122. Describe tracheal extubation and postoperative monitoring for infants and children with obstructive sleep apnea.
123. How should extubation after a difficult intubation be handled in infants and children?
Answers*
1. Difficult mask ventilation is defined as an inability to maintain oxygen saturation (Spo2) greater than 90% or an inability to prevent or reverse the signs of inadequate ventilation. (220)
2. The incidence of difficult mask ventilation ranges from 0.07% to 5%. (220)
3. Difficult tracheal intubation/laryngoscopy is defined as successful intubation requiring more than three attempts or taking longer than 10 minutes. (220)
4. Difficult tracheal intubation/laryngoscopy occurs in 1.1% to 8.5% of patients. (220)
5. Failed tracheal intubation occurs at an incidence of 0.01% to 0.03%. (220)
Anatomy and physiology of the upper airway
6. Resistance to airflow through the nasal passages is twice that through the mouth and accounts for approximately two thirds of total airway resistance. (220)
7. The ophthalmic (V1) and maxillary divisions (V2) of the trigeminal nerve (cranial nerve V) provide innervation to the nasal mucosa as the anterior ethmoidal, nasopalatine, and sphenopalatine nerves. (220, Figure 16-2)
8. The palatine nerves branch from the sphenopalatine ganglion to innervate the hard and soft palate. (220, Figure 16-2)
9. The mandibular division (V3) of the trigeminal nerve (cranial nerve V) forms the lingual nerve, which provides sensation to the anterior two thirds of the tongue. (220, Figure 16-3)
10. The posterior third of the tongue, the soft palate, and the oropharynx are innervated by the glossopharyngeal nerve (cranial nerve IX). (220, Figure 16-4)
11. The three components of the pharynx are the nasopharynx, the oropharynx, and the hypopharynx. (220)
12. The pharynx is innervated by cranial nerves IX (glossopharyngeal) and X (vagus). (220, Figures 16-4 and 16-5)
| Nerve | Sensory | Motor |
|---|---|---|
| Superior laryngeal, internal division |
Epiglottis Base of tongue Supraglottic mucosa Thyroepiglottic joint Cricothyroid joint |
None |
| Superior laryngeal, external division |
Anterior subglottic mucosa | Cricothyroid m. |
| Recurrent laryngeal |
Subglottic mucosa Muscle spindles |
Thyroarytenoid m. Lateral cricoarytenoid m. Interarytenoid m. Posterior cricoarytenoid m. |
14. The vocal cords are the narrowest portion of the adult airway. (220)
15. The cricoid cartilage is the most cephalad tracheal cartilage and is the only one that has a full ring structure. It is shaped like a signet ring, wider in the cephalocaudal dimension posteriorly. (220)
Airway assessment
16. Mallampati proposed a classification system (Mallampati score) to correlate the oropharyngeal space with the predicted ease of direct laryngoscopy and tracheal intubation. (223)
17. With the observer at eye level, the patient holds the head in a neutral position, opens the mouth maximally, and protrudes the tongue without phonating. (223)
18. Class I: The soft palate, fauces, uvula, and tonsillar pillars are visible.
Class II: The soft palate, fauces, and uvula are visible.
Class III: The soft palate and base of the uvula are visible.
Class IV: The soft palate is not visible. (223, Figure 16-6)
19. The Cormack and Lehane score classifies laryngoscopic view. (223)
20. Grade I: Most of the glottis is visible.
Grade II: Only the posterior portion of the glottis is visible.
Grade III: The epiglottis, but no part of the glottis, can be seen.
Grade IV: No airway structures are visualized. (223, Figure 16-7)
21. The ULBT correlates the patient’s ability to prognath the mandible with of the visualization of glottic structures on direct laryngoscopy. (225)
22. Class I: Lower incisors can bite above the vermilion border of the upper lip.
Class II: Lower incisors cannot reach vermilion border.
Class III: Lower incisors cannot bite upper lip. (225)
23. The laryngeal, pharyngeal, and oral axes must be aligned to obtain a line of vision during direct laryngoscopy. Flexion of the neck, by elevating the head approximately 10 cm, aligns the laryngeal and pharyngeal axes. Extension of the head on the atlanto-occipital joint aligns the oral and pharyngeal axes. These maneuvers place the head in the “sniffing” position and bring the three axes into optimal alignment. (225, Figure 16-8)
24. A thyromental distance (mentum to thyroid cartilage) less than 6 to 7 cm correlates with a poor laryngoscopic view. Three ordinary fingerbreadths approximate this distance. (226)
25. Decreased submandibular compliance correlates with poor laryngoscopic view. The submandibular space is the area into which the soft tissues of the pharynx must be displaced to obtain a line of vision during direct laryngoscopy. Anything that limits the size of this space or compliance of the tissue will decrease the amount of anterior displacement that can be achieved. (226)
26. Obesity is associated with difficulty in airway management. To increase the likelihood of successful endotracheal intubation, a wedge-shaped bolster placed behind the obese patient’s shoulders and back results in a more optimal sniffing position. (226)
27. In patients who do not have a prominent thyroid cartilage, identification of the cricoid cartilage can be achieved by beginning palpation of the neck at the sternal notch and sliding the fingers up the neck until a tracheal cartilage that is wider and higher (cricoid cartilage) than those below is felt. (226-227)
Airway management techniques
28. “Preoxygenation” describes the administration of oxygen to patients prior to the induction of anesthesia resulting in apnea. The goal is to achieve an end tidal oxygen level about 90%. Preoxygenation increases the duration of apnea without oxygen desaturation by filling the functional residual capacity with oxygen, thus increasing the patient’s reserve of oxygen while apneic. (227)
29. Methods by which to preoxygenate a patient prior to the induction of anesthesia include having the patient breathe 100% oxygen for 3 minutes or take eight deep breaths in 60 seconds. Although it was previously believed that having a patient take four deep breaths was sufficient for preoxygenation, this has been since proved not to be as effective as the other two methods. In obese patients, adequate preoxygenation may take longer. Having the obese patient sit in an upright position and applying continuous positive airway pressure may facilitate preoxygenation. (227)
30. Independent variables associated with difficult facemask ventilation include: (1) age older than 55 years, (2) a body mass index greater than 26 kg/m2, (3) a beard, (4) lack of teeth, (5) a history of snoring, (6) repeated attempts at laryngoscopy, (7) Mallampati class III to IV, (8) neck radiation, (9) male gender, and (10) limited ability to protrude the mandible. (227)
31. Ventilating pressure during facemask ventilation should be less than 20 cm H2O to avoid insufflation of the stomach. (227)
32. Nasal airways are relatively contraindicated in patients with coagulation or platelet abnormalities and those with basilar skull fractures. (228)
33. Indications for endotracheal intubation include:
(1) Provide a patent airway. (2) Prevent inhalation (aspiration) of gastric contents; (3) need for frequent suctioning; (4) facilitate positive-pressure ventilation of the lungs; (5) operative position other than supine; (6) operative site near or involving the upper airway; and (7) airway maintenance by mask difficult. (228, Table 16-5)
34. Cricoid pressure, also known as the Sellick maneuver, can be applied by an assistant exerting downward external pressure with the thumb and index finger on the cricoid cartilage to displace the cartilaginous cricothyroid ring posteriorly and thus compress the underlying esophagus against the cervical vertebrae. (228, Figure 16-10)
35. Conceptually, cricoid pressure should prevent spillage of gastric contents into the pharynx during the period from induction of anesthesia (unconsciousness) to successful placement of a cuffed endotracheal tube. This is thought to prevent, or minimize, the aspiration of gastric contents during the induction of anesthesia. The efficacy of cricoid pressure for this purpose is not clear. (229)
36. During laryngoscopy with a Macintosh blade, the distal end of the curved blade is advanced into the space between the base of the tongue and the pharyngeal surface of the epiglottis. During laryngoscopy with a Miller blade, the distal end of the straight blade is advanced beneath the laryngeal surface of the epiglottis. (229, Figure 16-12)
37. Depression or lateral movement of the patient’s thyroid cartilage externally on the neck (known as optimal external laryngeal manipulation [OELM] or backward upward rightward pressure [BURP]) with the laryngoscopist’s right hand may facilitate exposure of the glottic opening. (229)
38. Endotracheal tube sizes are specified according to their internal diameter (ID), which is marked on each tube. (230, Table 16-6)
39. Endotracheal tubes are radiopaque to ascertain the position of the distal tip relative to the carina. They are transparent to permit visualization of secretions or airflow as evidenced by condensation of water vapor in the lumen of the tube (“breath fogging”) during exhalation. (230)
40. Use of the minimum volume of air in a low-pressure, high-volume cuff that prevents air leaks during positive ventilation pressure (20 to 30 cm H2O) while also minimizing the likelihood of mucosal ischemia resulting from prolonged pressure on the tracheal wall. (231)
41. Serious complications attributable to endotracheal cuff pressure include ciliary denudation, tracheal stenosis, tracheal rupture, tracheoesophageal fistula, tracheocarotid fistula, and tracheoinnominate artery fistula. (231)
42. Stylets that can be used to facilitate endotracheal intubation include gum elastic bougie, Schroeder stylet, Frova intubating introducer, lighted stylets, and seeing optical stylets. (231-232)
43. Correct placement of an endotracheal tube is confirmed by:
44. Awake fiberoptic endotracheal intubation is most frequently chosen when a difficult tracheal intubation by direct laryngoscopy is anticipated. This technique is suited to these situations because it can be performed before inducing general anesthesia, thus eliminating the risk of failed tracheal intubation and failed ventilation in anesthetized patients. It is usually safest to maintain spontaneous breathing if there is a question about the ability to manage the patient’s airway. (233)
45. Fiberoptic endotracheal intubation is recommended for patients with unstable cervical spines because the technique does not require movement of the patient’s neck and can be performed before the induction of general anesthesia, thereby allowing for evaluation of the patient’s neurologic function after tracheal intubation and surgical positioning. (233)
46. Patients who have sustained an injury to the upper airway from either blunt or penetrating trauma are at risk for the endotracheal tube creating a false passage by exiting the airway through the disrupted tissue during direct laryngoscopy. By performing a fiberoptic intubation, not only can the injury be assessed, but the tracheal tube can also be placed beyond the level of the injury and thus eliminate the risk of causing subcutaneous emphysema, which could compress and further compromise the airway. (233)
47. An absolute contraindication to fiberoptic endotracheal intubation is a lack of time. The technique requires time to set up the equipment and prepare the patient’s airway for tracheal intubation. Therefore, if immediate airway management is required, another technique should be used. (233)
48. Relative contraindications to fiberoptic endotracheal intubation include lack of space around the scope, the presence of excessive blood or secretions, and the presence of a pharyngeal abscess. (233)
49. In general, the nasal route is easier than the oral route for fiberoptic endotracheal intubation because the angle of curvature of the endotracheal tube naturally approximates that of the patient’s upper airway. Additionally, nasal fiberoptic endotracheal intubation tends to be less of a stimulus for the gag reflex. A disadvantage of nasal fiberoptic endotracheal intubation is that the risk of inducing bleeding is higher when the nasal route is used. Therefore, the nasal route is relatively contraindicated in patients with platelet abnormalities or coagulation disorders. (233)
50. An antisialagogue (glycopyrrolate, 0.2 mg IV) should be administered to inhibit the formation of secretions that can obscure fiberoptic visualization. (233)
51. Sedation choices are numerous, but the depth of sedation should be titrated to reflect individual patient needs. Sedation should be administered cautiously in patients in whom the airway management is predicted to be difficult. (233)
52. The nasal mucosa must be anesthetized and vasoconstricted, which is typically done with either a 4% cocaine solution or a combination of 3% lidocaine and 0.25% phenylephrine. Local anesthetic solutions can be applied on soaked cotton-tipped swabs or pledgets. (233)
53. Topicalization of the tongue and oropharynx may be achieved by aerosolized local anesthetic or by performing bilateral blocks of the glossopharyngeal nerve at the base of each anterior tonsillar pillar. (233-234)
54. Topicalization or nerve blocks may be used for the larynx and trachea. Local anesthetic may be sprayed, aerosolized, or nebulized into the airway. It should be noted that the larger particle size of a spray tends to cause it to be deposited in the pharynx, with only a small proportion reaching the trachea. Conversely, the small particle size of a nebulized spray is carried more effectively into the trachea, but also into the smaller airways, where the anesthetic is not needed and undergoes more rapid systemic absorption. (234)
55. Lidocaine is the preferred topical local anesthetic because of its broad therapeutic window. Benzocaine can cause methemoglobinemia even in therapeutic doses. Tetracaine has a very narrow therapeutic window, and the maximum allowable dose (1.2 mg/kg) can easily be exceeded. Cetacaine is a mixture of benzocaine and tetracaine and has the disadvantages of each local anesthetic. (234)
56. Two blocks that can be performed to topicalize the larynx and trachea include the superior laryngeal nerve block and the transtracheal block. (234)
Flexible fiberoptic laryngoscopy
57. Softening the endotracheal tube in warm water before use makes it less likely to cause mucosal trauma or submucosal tunneling during nasal intubation. (234)
58. Inflation of the endotracheal tube cuff during advancement with the fiberoptic bronchoscope in the pharynx serves to create an enlarged pharyngeal space. Because secretions tend to adhere to the pharyngeal walls, endotracheal tube cuff inflation also helps keep the optics of the fiberoptic bronchoscope from being obscured. The inflated cuff further aims the tip of the endotracheal tube anteriorly. (234)
59. The appropriate depth of endotracheal tube placement can be verified by observing the distance between the carina and the tip of the endotracheal tube as the fiberoptic bronchoscope is withdrawn. (234)
60. If there is any resistance when removing the fiberoptic bronchoscope, the scope is either through the Murphy eye or kinked in the pharynx. In both instances, the endotracheal tube and the scope must be withdrawn together to prevent damaging the fiberoptic bronchoscope. (234)
61. Use of an oral intubating airway facilitates directing the bronchoscope during oral fiberoptic tracheal intubation. (235)
62. An important difference in performing fiberoptic laryngoscopy in an anesthetized patient is that the soft tissues of the pharynx, in contrast to the awake state, tend to relax and limit space for visualization with the fiberoptic bronchoscope. Using jaw thrust or a tonsil retractor, expanding the endotracheal tube cuff in the pharynx, or applying traction on the tongue, may overcome this problem. (235)
63. It is advisable to have a second person trained in anesthesia delivery assisting when a fiberoptic endotracheal intubation is performed under general anesthesia because it is difficult to maintain the patient’s airway, be attentive to the monitors, and perform the fiberoptic intubation alone. (235)
64. The Patil-Syracuse mask is designed with a port that will accommodate an endotracheal tube and a fiberoptic bronchoscope through a diaphragm. This device allows for spontaneous or controlled ventilation while fiberoptic nasal or oral endotracheal intubation is being performed. (235)
65. The Aintree catheter is an airway exchange catheter with connectors that allow ventilation with an anesthesia breathing circuit or jet ventilator. It differs from other exchange catheters by having a lumen of adequate size to accommodate a fiberoptic bronchoscope. (235)
Rigid fiberoptic laryngoscopes/videolaryngoscopes
66. Rigid fiberoptic laryngoscopes include the WuScope system, Bullard Laryngoscope, UpsherScope, GlideScope, McGrath Scope, Pentax-AWS, and Airtraq. These laryngoscopes may provide for better visualization of laryngeal structures and therefore facilitate endotracheal intubation in patients in whom direct laryngoscopy would otherwise be difficult. The laryngoscopes provide for better optics because of their rigid shape and/or because of the distal light source and optics on the laryngoscope blade. (235-236, Figure 16-6)
Retrograde tracheal intubation
Blind Nasotracheal Intubation
67. Retrograde endotracheal intubation involves threading a wire retrograde to the mouth through an external hole created by a needle in the cricothyroid membrane. The endotracheal tube can then be thread over the wire into the trachea with or without the aid of a fiberoptic bronchoscope. This technique may be useful in patients in which there is bleeding, limited mouth opening, or neck movement. It should not be performed in cases in which there is pathology.
Supraglottic airway devices
68. When correctly placed, the distal tip of the cuff should be against the upper esophageal sphincter (cricopharyngeus muscle), the lateral edges rest in the piriform sinuses, and the proximal end seats under the base of the tongue. (237-238)
69. The LMA Fastrach (Intubating LMA, ILMA) was designed to obviate the problems encountered when attempting to blindly intubate the trachea through a classic LMA. (238, Figure 16-18)
70. The ILMA is designed to be used with a silicone Euromedical endotracheal tube (size 7.0 ID, 7.5 ID, or 8.0 ID). These tracheal tubes exit the laryngeal mask at a different angle than do standard endotracheal tubes and thus result in better alignment with the airway. The ILMA is advanced into the pharynx by following the natural curvature of the patient’s upper airway. Because Euromedical tubes have low-volume, high-pressure cuffs, it is recommended that the largest size that is appropriate for the patient be used to minimize mucosal pressure from the cuff. (238)
71. The LMA CTrach is a modified LMA Fastrach with fiberoptic bundles located within the bowl of the mask and a lightweight viewer that attaches after the device is inserted. (238-239)
72. The ProSeal LMA is a modification of the classic LMA. The cuff of the ProSeal LMA extends onto the back of the mask, which results in an improved airway seal without increasing mucosal pressure. It has a second lumen that parallels the one for the airway, but opens at the distal tip of the mask to act as an esophageal vent. When optimally seated, the ProSeal LMA effectively isolates the trachea from the esophagus, thus protecting the lungs from aspiration when a minimum of 10 mL of air has been placed in the LMA cuff. (239, Figure 16-19)
73. The ETC is a double-lumen device that can function as either an endotracheal device or an esophageal obturator. It has been used successfully in emergency medical management and requires minimal training. (239)
Transtracheal techniques
74. Transtracheal jet ventilation is the administration of oxygen under high pressure through a needle placed in the cricothyroid membrane into the trachea. Transtracheal jet ventilation is contraindicated in patients with any upper airway disruption or obstruction. Risks of transtracheal jet ventilation include pneumothorax, pneumomediastinum, bleeding, infection, and subcutaneous emphysema. (241)
75. Cricothyrotomy is almost always performed under emergent circumstances when mask ventilation and/or endotracheal intubation are not possible. This technique involves the placement of a breathing tube through the cricothyroid membrane. (241)
Tracheal extubation
76. Tracheal extubation after general anesthesia must be performed when the patient is either deeply anesthetized or fully awake. Tracheal extubation during a light level of anesthesia (disconjugate gaze, breath holding or coughing, and not responsive to command) increases the risk for laryngospasm. (241)
77. Laryngospasm is an involuntary spasm/closure of the vocal cords that may present as stridor or attempts to breathe without air exchange. Laryngospasm is likely to occur during tracheal extubation, particularly under a light level of anesthesia, when vocal cords are stimulated by mucus, blood, or other substance.
78. Laryngospasm can be treated with mask ventilation with 100% oxygen and continuous positive airway pressure along with forward displacement of the mandible with the anesthesia provider’s index fingers to apply pressure at the temporomandibular joints. If laryngospasm persists, a small dose of an anesthetic induction agent or muscle relaxant may be used. (242-243)
79. Contraindications to deep tracheal extubation include previous difficult facemask ventilation or endotracheal intubation, risk of aspiration, and a surgical procedure that may have resulted in airway edema or increased airway irritability. (241)
80. Spontaneous ventilation with 100% oxygen is established before tracheal extubation. As with tracheal intubation, a functional residual capacity filled with oxygen allows for the longest safe period should breath holding or laryngospasm occur immediately after tracheal extubation. The effects of neuromuscular blocking drugs should be fully reversed. The oropharynx is suctioned just before tracheal extubation. The endotracheal tube cuff is deflated and the tracheal tube rapidly removed from the patient’s trachea and upper airway while a positive-pressure breath is delivered to help expel any secretions. After tracheal extubation, oxygen is delivered by facemask. (241)
81. Dental trauma is the most frequent type of damage related to direct laryngoscopy. (242, Table 16-9)
82. Flexion of the patient’s head may advance the tube up to 1.9 cm and convert an endotracheal placement into an endobronchial intubation, especially in children. Conversely, extension of the head can withdraw the tube up to 1.9 cm and result in pharyngeal placement. (242)
83. Laryngospasm and aspiration of gastric contents are the two most serious potential immediate complications after tracheal extubation. (242-243)
84. The major complication of prolonged tracheal intubation (>48 hours) is damage to the tracheal mucosa, which may progress to destruction of cartilaginous rings and subsequent scar formation and tracheal stenosis. Stenosis becomes symptomatic when the adult tracheal lumen is decreased to less than 5 mm. (243)
Airway management in infants and children
85. The difference between the infant and adult airway includes positioning of the larynx in the neck, tongue size, epiglottis size, size of the head relative to the body, neck length, nares size, and location of the narrowest point. Usually by the time the child is about 10 years old, the upper airway has taken on more adultlike characteristics. (243, Table 16-10)
86. The infant larynx is located higher in the neck at the level of C3-C4. In adults the larynx is at the level of C4-C5. In infants this causes the tongue to shift more superiorly, closer to the palate. The tongue more easily apposes the palate, which can cause airway obstruction in situations such as the inhalation induction of anesthesia. (243)
87. An infant’s tongue is larger in proportion to the size of the mouth than in adults. The relatively large size of the tongue makes direct laryngoscopy more difficult and can contribute to obstruction of the upper airway during sedation, inhalation induction of anesthesia, or emergence from anesthesia. (243)
88. The epiglottis in an infant’s airway is often described as relatively larger, stiffer, and more omega shaped than an adult epiglottis. More importantly, an infant’s epiglottis is typically angled in a more posterior position, thereby blocking visualization of the vocal cords during direct laryngoscopy. (243)
89. In infants and small children, it is often necessary to lift the epiglottis with the tip of the blade of the laryngoscope to visualize the vocal cords and successfully intubate the trachea. Straight laryngoscope blades, which have a smaller profile than curved laryngoscope blades, more easily fit in the smaller infant mouth. Straight laryngoscope blades with their narrower tips also more effectively lift the epiglottis allowing better visualization of the vocal cords. (243)
90. The narrowest portion of an infant’s airway is at the cricoid cartilage, whereas the narrowest portion of an adult’s airway is at the vocal cords. (243)
91. The correct size uncuffed endotracheal tube is one that results in an air leak around the endotracheal tube with the application of 20 to 25 cm H2O positive pressure. (243)
92. Cuffed endotracheal tubes can be used in infants and children if the inflation of the cuff is carefully adjusted and monitored so that the leak pressure remains at 20 to 25 cm H2O. If nitrous oxide is used during the anesthetic, the nitrous oxide will diffuse into the air-filled cuff and increase both its volume and the pressure transmitted to the underlying tracheal mucosa. (243)
93. If the leak pressure is too high with either a cuffed or uncuffed endotracheal tube, the tracheal mucosa will be compressed causing subglottic edema either at the level of the cricoid cartilage or below. This complication can result in postextubation croup or stridor in mild cases and tracheal stenosis in more severe cases involving prolonged tracheal intubation. (243)
94. An infant’s head and occiput are relatively larger than an adult’s. The proper position for direct laryngoscopy and tracheal intubation in an adult is often described as the sniffing position with the head elevated and the neck flexed at C6-C7 and extended at C1-C2. An infant, on the other hand, requires a shoulder roll or neck roll to establish an optimal position for facemask ventilation and direct laryngoscopy. (243)
95. Infant’s nares are relatively smaller than an adult’s. This can offer significant resistance to airflow, and increase the work of breathing, especially when secretions, edema, or bleeding narrow them. (243-244)
96. A history of snoring should prompt additional questioning about whether the child has obstructive sleep apnea and should alert the anesthesia provider that respiratory obstruction may develop during the induction and emergence phases of anesthesia, as well as in the postoperative period. This is of particular concern if opioids are given for pain management. (244)
97. Preanesthetic medication can facilitate separation of the infant or child from the parents before the induction of anesthesia. Preanesthetic medication is often not necessary in infants younger than 6 months because stranger anxiety does not usually develop until 6 to 9 months of age. (244)
98. Midazolam syrup can be given orally (2 mg/mL) in a dose of 0.5 mg/kg up to a maximum dose of about 20 mg. If the child is uncooperative with taking oral midazolam and preanesthetic medication is essential, midazolam can also be given intranasally, intramuscularly, or rectally. (244)
99. In a child without an intravenous catheter in place, the induction of anesthesia with the odorless mixture of nitrous oxide and oxygen through a facemask and then slowly increasing the concentration of sevoflurane is the best approach in a cooperative child. When the infant or child becomes unconscious, the nitrous oxide should be turned off to administrate 100% oxygen to the child. (244)
100. Airway obstruction during mask induction in infants and children can usually be relieved by opening the mouth, extending the neck, and pushing anteriorly on the angle of the jaw. Occasionally, an oral or nasal airway may need to be inserted. (244)
101. The weight of the infant or child determines the appropriate size of LMA. (245)
102. The LMA Flexible has a wire-reinforced airway tube that resists kinking and can be positioned in such a way that interference with surgical procedures involving the head and neck is minimized. (245)
103. The major advantage of the Air-Q ILA is a design that facilitates endotracheal intubation with standard oral endotracheal tubes. The airway tube has a larger diameter than the LMA, allowing for intubation with a larger ETT than the correspondingly sized LMA. In addition, the Air-Q ILA can be used with a specially designed ILA removal stylet that stabilizes the ETT and allows controlled removal of the ILA without dislodging the ETT from the trachea. (245-246)
104. The appropriately sized endotracheal tube for infants and children can be estimated by using the following formula:
105. The formula is for uncuffed endotracheal tubes. (246)
106. When using a cuffed endotracheal tube in infants and children, the formula used to estimate the appropriate-sized uncuffed endotracheal tube must be adapted. To adapt the formula it is necessary to subtract half a size from the calculated size to estimate the appropriate size cuffed endotracheal tube. (246)
107. The new Microcuff pediatric endotracheal tubes appear to offer several distinct advantages over conventional pediatric cuffed endotracheal tubes. The Microcuff endotracheal tubes have a cuff that is made from a microthin polyurethane membrane that, while stronger than conventional cuffs, seals the airway at lower cuff pressures than conventional endotracheal tubes. This reduces the potential for mucosal edema and postextubation croup. The cuff on the Microcuff endotracheal tube is also shorter and placed closer to the tip of the endotracheal tube, increasing the chances that the endotracheal tube is correctly placed. The Microcuff endotracheal tube also has an intubation depth mark, which indicates the correct depth for insertion and also increases the ability for correct placement. (246)
108. Using a stylet stiffens the endotracheal tube and makes it easier to manipulate during direct laryngoscopy and tracheal intubation. The trachea of infants and small children can often be intubated without using a stylet, but a stylet may be useful for whenever a difficult tracheal intubation is anticipated. Even if intubating without a stylet, the appropriately sized stylet should always be immediately available. (246, Table 16-6)
109. The disadvantage of a straight blade is that it does not retract the tongue as well to the left side of the mouth. A curved blade has a larger flange that retracts the tongue to the left more effectively and may be useful in certain patient populations in which the tongue is larger than normal. (246-247)
110. In infants younger than 1 year, a Miller 1 straight laryngoscope blade is most useful. In children between 1 and 3 years of age, a 1½ straight laryngoscope blade, such as a Wis-Hipple, is often useful. A longer straight laryngoscope blade such as a Miller 2 is appropriate for most children between 3 and 10 years of age. The tracheas of children older than 11 years are often more easily intubated with a curved laryngoscope blade such as a Macintosh 3. Both straight and curved laryngoscope blades of various sizes should always be available. (247)
111. When an unexpected difficult airway appears in pediatric patients, the most important first step is to call for an additional anesthesia colleague to help. (247, Figure 16-23)
112. It is critical to not persist with repeated attempts at direct laryngoscopy, which can result in trauma to the upper airway, edema, and bleeding. In most situations, an LMA should be inserted to provide an airway to oxygenate and ventilate the patient and allow time to obtain additional personnel and airway equipment. An LMA may be the only way to maintain an airway until the patient wakes up or a surgical airway is established. An LMA is also an excellent conduit for fiberoptic intubation. (247)
113. It is unlikely that infants and children will cooperate with procedures such as an awake fiberoptic endotracheal intubation, so it is usually necessary to induce anesthesia and manage the airway with the patient asleep. (247)
114. An additional anesthesia colleague should be available for help during the induction of anesthesia, inserting an intravenous line, and securing the airway. A surgeon capable of establishing a surgical airway and emergency airway equipment should be in the operating room before beginning the induction of anesthesia. (247)
115. Lighted stylets, the GlideScope video laryngoscope, and fiberoptic bronchoscopes are all available in smaller sizes to facilitate intubation of a child with a difficult airway. (247-248)
116. Infants and small children are at a more likely risk than adults for croup, stridor, and laryngospasm after tracheal extubation. (248)
117. Croup occurs most commonly when either a cuffed or uncuffed endotracheal tube is used that is too large or when the cuff is inflated with too much air. The resulting mechanical pressure on the tracheal mucosa causes venous congestion and edema, and in severe cases can even compromise the arterial blood supply causing mucosal ischemia. The resulting edema can narrow the tracheal lumen, especially in infants and small children. Because resistance to flow in an endotracheal tube is inversely proportional to the radius of the lumen to the fourth power, 1 mm of edema in an infant airway is much more significant than 1 mm of edema in an adult airway. Other risk factors for croup include multiple tracheal intubation attempts, unusual positioning of the head during surgery, increased duration of surgery, and procedures involving the upper airway, such as rigid bronchoscopy. (248-249)
118. An infant or child with postextubation croup usually has respiratory distress in the postanesthesia care unit. Nasal flaring, retractions, an increased respiratory rate, audible stridor, and decreased oxygen saturation are common clinical findings. (249)
119. Treatment of postextubation croup or stridor depends on the degree of respiratory distress. Mild symptoms can be managed with humidified oxygen and prolonged observation in the postanesthesia care unit. More severe cases may require aerosolized racemic epinephrine and postoperative observation in an intensive care unit. Patients whose respiratory distress is severe and not relieved with these measures may need to be reintubated with an endotracheal tube smaller than the one previously used. Steroids administered intravenously for preventing upper airway edema are more beneficial when given before the airway is instrumented and should be administered before procedures such as rigid bronchoscopy. (249)
120. Infants and children with obstructive sleep apnea are at significant risk for airway obstruction, respiratory distress, and the potential for apnea in the postoperative period. At baseline these infants and children hypoventilate, which results in hypercapnia and often arterial hypoxemia while asleep. Residual inhaled anesthetics or residual neuromuscular blockade can depress airway reflexes, skeletal muscle tone and strength, and respiratory drive, and result in significant airway compromise in infants and children with obstructive sleep apnea. (249)
121. Opioids must be very carefully titrated both intraoperatively and postoperatively because they can depress the ventilatory drive and contribute to significant hypercapnia and arterial hypoxemia in these infants and children. (249)
122. Tracheal extubation in patients with obstructive sleep apnea should be considered only when these infants and children are fully awake. All infants and children with obstructive sleep apnea should be monitored postoperatively with pulse oximetry and apnea monitoring. High-risk patients should be monitored postoperatively in an intensive care unit setting. (249)
123. Tracheal extubation of an infant or child after a difficult intubation is considered carefully because reintubation can be more difficult than the initial intubation. The tracheas of infants and children with difficult airways should be extubated only when they are fully awake and there is no residual neuromuscular blockade. An infant or child with a difficult airway should be extubated only when appropriate equipment and personnel are available for urgent reintubation. (250)
