Lippincott's Anesthesia Review: 1001 Questions and Answers

Chapter 2. Airway Management

Yuriy Bronshteyn

    1.   A major difference between the adult and neonatal airway is that the

          A.   Neonate’s larynx is located more superiorly in the neck

          B.   Neonate’s epiglottis is angled more superiorly

          C.   Narrowest segment of a neonate’s upper airway occurs at the level of the vocal cords

          D.   Neonate is at lower risk of postextubation stridor compared to the adult

    2.   The narrowest segment of a 14-day-old child’s upper airway is located at the

          A.   Hyoid bone

          B.   Thyroid cartilage

          C.   Vocal cords

          D.   Subglottic region

    3.   Airway obstruction in Pierre Robin syndrome most likely occurs

          A.   Between the tongue and pharyngeal wall

          B.   At the level of the glottis

          C.   In the subglottic trachea

          D.   At the bronchial level

    4.   Airway management in Klippel–Feil syndrome is most likely to be challenging because of

          A.   Micrognathia

          B.   Macroglossia

          C.   Subglottic stenosis

          D.   Cervical spine fusion

    5.   One of the following statements regarding airway management in patients with congenital syndromes is most accurate:

          A.   Laryngoscopy is often challenging in Turner syndrome because of a high frequency of laryngeal distortion

          B.   Airway management in Treacher Collins syndrome is complicated by a high incidence of cervical spine instability

          C.   Intubation in patients with Goldenhar syndrome is often challenging due to a high rate of subglottic stenosis

          D.   Airway management of patients with trisomy 21 is complicated by a high incidence of cervical spine instability

    6.   A healthy 2-year-old male is scheduled to undergo a laparoscopic inguinal hernia repair. His airway was managed uneventfully with mask ventilation followed by direct laryngoscopy and intubation with a 4.5-mm uncuffed endotracheal tube (ETT). Manual ventilation produces an air leak in the oropharynx beginning at a peak pressure of 20 cm H2O. The best next step in the anesthetic management is to

          A.   Continue current management

          B.   Replace the ETT with a smaller-sized uncuffed tube

          C.   Replace the ETT with a larger-sized uncuffed tube

          D.   Replace the ETT with a 4.0-mm cuffed ETT

    7.   A 4-year-old patient scheduled for laparoscopic gastrostomy tube placement undergoes induction of general anesthesia and endotracheal intubation with a 4.5-mm cuffed endotracheal tube. The tube is taped 14 cm at the gumline, and the patient is placed on volume-control ventilation. The most likely first sign of a right main stem intubation is

          A.   Arterial desaturation

          B.   Hypercapnia

          C.   Increased peak inspiratory pressures

          D.   Hypotension

    8.   A 6-year-old patient scheduled for laparoscopic bilateral inguinal hernia repair undergoes inhalational induction and intubation with a 5.0-mm cuffed endotracheal tube. The tube is secured with the 15-cm mark at the patient’s gumline. Auscultation reveals equal breath sounds bilaterally. Inflation of the pilot balloon results in palpation of the inflated tube cuff just above the cricoid cartilage. A leak test reveals leak of air into the oropharynx at a positive pressure of 20 cm H2O. The next best step in management is

          A.   No change in anesthetic care is indicated

          B.   The tube cuff should be deflated until a leak is present starting at 15 cm H2O of positive pressure

          C.   The tube cuff should be deflated and the tube advanced until the cuff, when inflated, is palpable below the cricoid cartilage

          D.   The tube cuff should be deflated and the tube withdrawn until ventilator peak pressures decrease

    9.   A 4-year-old boy with autism and failure-to-thrive undergoes a gastrostomy tube placement. At the completion of the operation, the patient remains unresponsive but is breathing spontaneously and has a mild gag response to oral suctioning. The anesthesiologist extubates the patient and immediately shuts off the volatile agent. The anesthesiologist then inserts an appropriately sized oropharyngeal airway and places a face mask connected to the ventilator circuit over the patient’s face, allowing the patient to breathe 100% oxygen. Despite providing a chin lift, jaw thrust, and positive-pressure breaths, the anesthesiologist notes that the ventilator shows no end-tidal carbon dioxide. Auscultation over the sternal notch reveals no air movement. The pulse oximeter reading then rapidly drops to 70% from 100%. The next best step in management is

          A.   Administration of albuterol

          B.   Insertion of a nasal trumpet

          C.   Endotracheal reintubation

          D.   Administration of succinylcholine

  10.   In the scenario above, if the patient’s postextubation condition is left untreated, the patient will most likely experience

          A.   Aspiration

          B.   Bronchospasm

          C.   Pulmonary edema

          D.   Croup

  11.   A 2-year-old child weighing 13 kg is scheduled for inguinal hernia repair. She is at the 55th percentile for height for her age. An appropriately-sized cuffed endotracheal tube for this patient will have an internal diameter of

          A.   3.0 mm

          B.   4.0 mm

          C.   5.0 mm

          D.   6.0 mm

  12.   The superior surface of the epiglottis is innervated by the

          A.   Hypoglossal nerve

          B.   Recurrent laryngeal nerve

          C.   Internal branch of the superior laryngeal nerve

          D.   External branch of the superior laryngeal nerve

  13.   Tactile sensation from the anterior third of the tongue is carried by fibers of the

          A.   Trigeminal nerve

          B.   Facial nerve

          C.   Glossopharyngeal nerve

          D.   Hypoglossal nerve

  14.   A 48-year-old female patient with temporomandibular joint dysfunction and associated limited mouth opening is scheduled for a thyroidectomy for goiter. Due to concern for challenging laryngoscopy, the anesthesiologist elects to perform an awake fiberoptic intubation. In order to anesthetize the posterior third of the tongue, the anesthesiologist should perform a nerve block of the

          A.   Cranial nerve V

          B.   Cranial nerve VII

          C.   Cranial nerve IX

          D.   Cranial nerve XII

  15.   A patient who suffers acute, bilateral denervation of the external branch of the superior laryngeal nerve will most likely present with

          A.   No symptoms

          B.   Hoarseness

          C.   Stridor

          D.   Aspiration

  16.   To anesthetize the supraglottic laryngeal mucosa, the local anesthetic should be injected into one of the following areas:

          A.   The base of the anterior tonsillar pillar

          B.   Medial to the lesser cornu of the hyoid bone

          C.   Superior to the superior cornu of the thyroid cartilage

          D.   Through the cricothyroid membrane

  17.   The efferent limb of the glottic closure reflex, which is involved in laryngospasm, primarily involves the

          A.   Internal branch of the superior laryngeal nerve

          B.   Hypoglossal nerve

          C.   Recurrent laryngeal nerve

          D.   Glossopharyngeal nerve

  18.   A 65-year-old woman undergoes a thyroidectomy for papillary thyroid cancer. Immediately after emergence and extubation, she is aphonic and has minimal chest movement, despite spontaneously moving her limbs and head. Auscultation reveals lack of breath sounds over the chest. There is no evidence of a surgical site hematoma. The anesthesiologist provides a jaw thrust and positive-pressure breaths, which slightly improve the patient’s oxygenation and ventilation. The surgeon suggests a bilateral block of both the internal and external branches of the patient’s superior laryngeal nerve. If performed this block would likely result in

          A.   Worsening of the patient’s respiratory distress and no change in her aphonia

          B.   Improvement of the patient’s respiratory distress and no change in her aphonia

          C.   No change in the patient’s respiratory distress and improvement of her aphonia

          D.   No change in the patient’s respiratory distress and no change in her aphonia

  19.   A 48-year-old woman with temporomandibular joint dysfunction and limited mouth opening is scheduled for thyroidectomy for goiter. Due to concern for a difficult laryngoscopy, the anesthesiologist elects to perform an awake oral fiberoptic intubation. To reliably blunt the afferent limb of the cough reflex, the anesthesiologist should perform a bilateral block of the

          A.   Superior laryngeal nerve and the recurrent laryngeal nerve

          B.   Glossopharyngeal nerve and internal branch of the superior laryngeal nerve

          C.   Glossopharyngeal nerve and external branch of the superior laryngeal nerve

          D.   Internal and external branches of the superior laryngeal nerve

  20.   If an adult patient were to suffer an acute, bilateral transection of cranial nerve X, awake laryngoscopy would most likely reveal

          A.   Fully adducted vocal cords

          B.   Fully abducted vocal cords

          C.   Vocal cords in a partially adducted position with 2 to 3 mm of space between them

          D.   Vocal cords oscillating between adducted and abducted position

  21.   Several hours after undergoing repair of an ascending aortic dissection, a 65-year-old male patient is extubated in the intensive care unit. All of the arch vessels were preserved during the operation. After extubation, the patient’s voice is noted to be hoarse. Awake fiberoptic laryngoscopy would most likely show the following during inspiration:

          A.   Vocal cords in a fully abducted position

          B.   Vocal cords in a fully adducted position

          C.   Left vocal cord in an adducted position and right vocal cord fully abducted

          D.   Left vocal cord in an abducted position and right vocal cord fully adducted

  22.   An awake tracheostomy would be facilitated by a regional block of the

          A.   Trigeminal nerve

          B.   Glossopharyngeal nerve

          C.   Superior laryngeal nerve

          D.   Recurrent laryngeal nerve

  23.   One of the following statements regarding the innervation of airway structures is most correct:

          A.   The afferent limb of the gag reflex is primarily carried by fibers of the recurrent laryngeal nerve

          B.   Trigeminal nerve block would facilitate awake nasotracheal intubation

          C.   The superior surface of the epiglottis is primarily innervated by the glossopharyngeal nerve

          D.   Tactile sensation from the posterior one-third of the tongue is carried by the hypoglossal nerve

  24.   A nasal trumpet would be most appropriate for management of anesthetic-induced upper airway obstruction in one of the following patients:

          A.   A 25-year-old passenger ejected out of a motorcycle now with Glasgow Coma Scale of 13 and some periorbital bruising

          B.   A 32-year-old term parturient, otherwise healthy except for gestational thrombocytopenia, who requires emergent cesarean section under general anesthesia

          C.   A 45-year-old female with temporomandibular joint syndrome and breast cancer scheduled for bilateral mastectomy

          D.   A 65-year-old male with a mechanical mitral valve on therapeutic anticoagulation undergoing emergent coronary catheterization for unstable angina

  25.   A 55-year-old woman with severe anxiety and rheumatoid arthritis is scheduled for thyroidectomy for medullary thyroid cancer. Her airway exam in the upright position is notable for a nonvisible uvula with the tongue protruded, a 2 fingerbreadth mouth opening, a thyromental distance of 2.5 fingerbreadths, and neck range-of-motion at the atlanto-occipital joint of about 70 degrees. Examination of her neck reveals an enlarged, fixed, and nonmobile mass that appears to be contiguous with the thyroid gland when the patient swallows. The trachea cannot be palpated. The patient is highly anxious and tells you that under no circumstance will she let you insert a “breathing tube inside my airway while I’m awake.” The next best step in anesthetic management is

          A.   Induction of general anesthesia followed by fiberoptic bronchoscopy

          B.   Induction of general anesthesia followed by rigid bronchoscopy

          C.   Induction of general anesthesia followed by laryngeal mask airway placement

          D.   Cancel the case

  26.   After rapid sequence induction of general anesthesia, a patient is unable to be intubated. Subsequent attempts at ventilation by face mask and a supraglottic airway device are also unsuccessful. One of the following statements regarding transtracheal jet ventilation and surgical cricothyrotomy in this situation is most correct:

          A.   Transtracheal jet ventilation does not require a patent natural airway

          B.   Ventilation through a surgical cricothyrotomy allows both inhalation and exhalation to occur

          C.   The development of laryngospasm during ventilation through a cricothyrotomy would rapidly cause pulmonary overinflation and barotrauma

          D.   Transtracheal jet ventilation can be continued for a longer period of time than can ventilation via a cricothyrotomy

  27.   Use of a laryngeal mask airway would be most appropriate for airway management in the following patient:

          A.   An obese patient with acute appendicitis who, after rapid sequence induction, cannot be intubated

          B.   An elderly patient with restrictive lung disease scheduled for inguinal hernia repair

          C.   An obese male patient with a hiatal hernia and GERD scheduled for umbilical hernia repair

          D.   A full-term parturient brought to the OR for emergent cesarean section because of fetal bradycardia

  28.   After undergoing an uneventful operation, one of the following patients would be the best candidate for “deep extubation”:

          A.   A 23-year-old woman with asthma who has just undergone an exploratory laparotomy for small bowel obstruction

          B.   A 65-year-old man with gastroesophageal reflux who has just undergone an inguinal hernia repair

          C.   An 18-year-old patient with scoliosis who has just undergone a 6-hour posterior thoracolumbar spinal instrumentation and fusion

          D.   A 64-year-old female with coronary artery disease who has just undergone a total hip arthroplasty under general anesthesia

  29.   One of the following is a primary risk factor for difficult mask ventilation:

          A.   Limited mouth opening

          B.   Thyromental distance less than 3 fingerbreadths

          C.   High arched palate

          D.   Inability to bring mandibular incisors anterior to the maxillary incisors

  30.   An otherwise healthy patient with a history of daytime sleepiness and snoring from laryngeal papillomatosis undergoes polysomnography and spirometry, which shows dynamic inspiratory obstruction. The flow–volume loop that would be most consistent with this patient’s condition is

images

Figure 2-1

          A.   Figure 2-1A

          B.   Figure 2-1B

          C.   Figure 2-1C

          D.   Figure 2-1D

CHAPTER 2 ANSWERS

    1.   A.   The neonate’s larynx is located more superiorly in the neck than the adult’s. The location of the adult’s larynx is at C4–C5 level of the spine, while the neonate’s is at C3–C4 level. The neonate’s epiglottis is relatively longer, stiffer, and angled more posteriorly compared to the adult’s, which is one of the reasons why straight blades are more popular among pediatric anesthesiologists. The narrowest part of the upper airway is at the level of the cricoid cartilage in neonates, and at the level of the vocal cords in adults. The child’s airway takes on adult characteristics between the ages of 5 and 10 years. The neonate is at greater risk of postextubation stridor compared to the adult. Resistance through a cylindrical tube (such as the trachea) is inversely proportional to the radius raised to the fourth power (Poiseuille law). Thus, a 1-mm reduction in tracheal diameter due to edema results in a marked rise in airway resistance in small children, which may be inconsequential in adults.

    2.   D.   According to classical teaching, the narrowest portion of a child’s upper airway is at the level of the cricoid cartilage, whereas the narrowest portion of an adult’s upper airway is at the level of the vocal cords. However, a more recent bronchoscopic study of airway dimensions in children found that between the ages of 6 months and 13 years, the glottis, not the cricoid cartilage, is the narrowest portion of the child’s airway. This study did not measure airway dimensions in children younger than 6 months.

    3.   A.   Pierre Robin is a congenital syndrome associated with enlarged tongue, small mouth, and mandibular anomalies typically manifested as micrognathia. All of these limit the oropharyngeal space, contributing to airway obstruction between the tongue and posterior pharyngeal wall. When you see Pierre Robin, think PR: Posterior Restriction behind the tongue.

    4.   D.   Klippel–Feil is a congenital syndrome associated with the phenotypical triad of short neck, low posterior hair line, and congenital spinal fusion causing limited neck mobility. Fused segments of the cervical spine in patients with this syndrome promote hypermobility at unfused spine segments, increasing the risk of neurologic compromise during neck manipulation. When you see Klippel–Feil, think KF: Cervical Fusion.

    5.   D.   Airway management of patients with trisomy 21 (Down syndrome) is complicated by several factors. These patients tend to have small mouths and large tongue, resulting in limited oropharyngeal space. They are prone to laryngospasm. They also have a high incidence of subglottic stenosis, such that endotracheal tubes should be downsized by 0.5 mm from the caliber expected for a patient of the same size without Down syndrome. Finally, they have a high incidence of cervical spine instability. The other three syndromes share a common feature of micrognathia (small jaw), which renders these patients a challenge for direct laryngoscopy. Turner syndrome occurs in females who lack a complete second X chromosome (monosomy). These women tend to have short necks and small jaws. Laryngeal distortion (choice A) has not been described in this population. Treacher Collins is a rare syndrome characterized by abnormal development of facial bones (e.g., maxillary and mandibular). A high incidence of cervical spine instability (choice B) has not been described in this population. Goldenhar syndrome is manifested by dysplastic growth of the face (especially the ears, eyes, and mouth) and vertebral anomalies (e.g., scoliosis). A high incidence of subglottic stenosis (choice D), although a common finding in patients with trisomy 21, has not been described in the Goldenhar population.

    6.   A.   A positive-pressure leak test provides information about the tightness of the seal formed between an ETT and its surrounding mucosa. A leak at pressures below 25 cm H2O places the tracheal mucosa at a very low risk of ischemic injury. Pressures above 30 cm H2O, the arteriolar-capillary perfusion pressure, can cause mucosal ischemia, with resulting inflammation, ulceration, stridor, and later scarring and stenosis.

    7.   C.   When an endotracheal tube migrates from an intratracheal to an endobronchial position while on volume-control ventilation, the first sign of migration is generally an increase in peak inspiratory pressures. Peak inspiratory pressure results from the resistance to flow of the large airways and the static compliance of the lung. A fixed volume of air moving out of an endobronchial tube would encounter significantly more large airway resistance compared to the same volume moving out of an endotracheal tube (remember: resistance is inversely proportional to radius raised to the fourth power). Thus, the first sign of an endobronchial intubation would be an elevation in peak inspiratory pressures. Because the nonventilated lung has some reserve of oxygen, passive oxygenation would delay onset of hypoxemia briefly (choice A). Hypercapnia (choice B) would eventually develop in an endobronchially intubated patient on controlled ventilation if the minute ventilation were kept constant. Hypotension (choice D) might occur if the right lung is allowed to hyperinflate, restricting venous return. However, this would not be as immediate as a rise in peak inspiratory pressures.

    8.   C.   Palpation of the endotracheal tube cuff palpable above the cricoid cartilage implies that the cuff’s position is intralaryngeal. This is problematic for two reasons: (1) an inflated cuff in the larynx may cause laryngeal injury and postoperative respiratory compromise, and (2) such a high tube position may increase the risk of inadvertent extubation. The cuff should be deflated and the tube advanced until the cuff (when inflated) is palpable below the cricoid cartilage. Choice B is incorrect: a cuff inflated to enable air leak at 20 to 25 cm H2O of positive pressure should not cause airway injury and edema in routine circumstances. Choice D would likely result in the tip of the endotracheal tube moving from an intralaryngeal to a supralaryngeal position.

    9.   D.   The scenario describes extubation of a child during a “light” plane of anesthesia when laryngeal reflexes are hypersensitive. Return of a gag reflex is a characteristic of this lighter, hyperexcitable stage. If a patient is extubated while lightly anesthetized, there is an increased risk of laryngospasm. Stimulation of the laryngeal mucosa by secretions or a foreign body (e.g., the endotracheal tube or an oral airway) can result in laryngospasm during the excitation stage of anesthesia or sometimes even during awake states.

                Laryngospasm and other causes of upper airway obstruction (e.g., tongue collapsed against the posterior pharyngeal wall) may not be immediately distinguishable. However, the initial treatment is identical: anterior displacement of the mandible using a chin lift or jaw thrust combined with positive-pressure ventilation. If these measures fail to relieve the laryngospasm and hypoxemia develops, pharmacologic therapy should be initiated emergently. In a patient with no contraindications, a small dose of succinylcholine (0.25–0.5 mg/kg) or deepening of the anesthetic (e.g., with propofol or another general anesthetic) should break the laryngospasm.

  10.   C.   Left untreated, upper airway obstruction in a spontaneously breathing patient can result in the development of negative-pressure pulmonary edema (also called postobstructive pulmonary edema). Forceful inspiration against a closed upper airway generates a large negative intrathoracic pressure which can result in pulmonary edema by increasing capillary transmural pressure and/or by acutely elevating left ventricular end-diastolic pressure. Aspiration (choice A) would be impossible during laryngospasm. Bronchospasm (choice B) would not be expected as a direct consequence of prolonged laryngospasm. Croup or laryngotracheal bronchitis (choice D) is a form of upper airway obstruction that typically occurs in response to a viral or bacterial upper respiratory tract infection in children between the ages of 6 months and 6 years. This clinical scenario is not suggestive of an infectious etiology for the upper airway obstruction.

  11.   B.   A commonly used formula for estimating the internal diameter of an uncuffed endotracheal tube in children is

Internal diameter (in mm) = (Age + 16)/4

         The resulting value should be reduced by 0.5 mm when using a cuffed endotracheal tube to allow space in the tracheal lumen for cuff inflation. Since this child appears to have a height and weight appropriate for her age, the formula would be reasonable to use. For the patient in this question, the internal diameter is (2 + 16)/4 = 4.5 mm for an uncuffed tube, which is reduced to 4.0 mm for a cuffed tube.

  12.   C.   The vagus nerve provides sensory innervation to the structures of the airway beginning with the epiglottis and moving caudally. It has two major branches that innervate distinct parts of the airway: the superior laryngeal nerve (SLN) and recurrent laryngeal nerve (RLN). Above the vocal cords, the sensory innervation of the larynx is via the SLN. Below the vocal folds, sensory innervation of the airway is provided by branches of the recurrent RLN. The vocal cords themselves receive dual innervation from both nerves. The SLN has two branches: internal and external. The internal SLN branch (choice C) is exclusively a sensory nerve that innervates both the superior and inferior surfaces of the epiglottis. The external branch of the SLN is a motor nerve that innervates the cricothyroid muscle (Fig. 2-2). The RLN (choice B) is a mixed motor and sensory nerve. The motor branch innervates all of the laryngeal muscles, except the cricothyroid muscle, while the sensory branch innervates the subglottic mucosa of the airway. The hypoglossal nerve (choice A) is a purely motor nerve that innervates the muscles of the tongue.

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Figure 2-2.  Subdivisions of the superior laryngeal nerve in the sagittal view.

  13.   A.   The tongue has innervation for both gustatory (aka “taste”) and tactile (general sensory) input. Gustatory (taste) sensation for the anterior two-thirds of the tongue is provided by the facial nerve (CN VII), and for the posterior third of the tongue by the glossopharyngeal nerve (CN IX). Tactile sensation for the anterior two-thirds of the tongue is provided by the trigeminal nerve (CN V), and for the posterior one-third of the tongue by the glossopharyngeal nerve (CN IX). In addition, a small portion of sensory innervation of the posterior tongue is provided by fibers of the superior laryngeal nerve’s internal branch (“spillover fibers” from that nerve’s innervation of the epiglottis) (Fig. 2-3). The hypoglossal nerve (choice D) is a purely motor nerve that innervates the muscles of the tongue.

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Figure 2-3.  General sensory innervation of tongue.

  14.   C.   The glossopharyngeal nerve (CN IX) is a mixed motor and sensory nerve. Its sensory fibers carry information about general sensation and taste from the posterior third of the tongue (Fig. 2-3). Of note, the glossopharyngeal nerve does not provide sensory innervation to the epiglottis; it is provided by the superior laryngeal nerve. The trigeminal nerve (CN V) (choice A) carries general sensory information from the anterior two-thirds of the tongue. The facial nerve (CN VII) (choice B) is a mixed motor and sensory nerve. It carries taste sensation from the anterior two-thirds of the tongue and oral cavity. The hypoglossal nerve (CN XII) (choice D) is a purely motor nerve that innervates the muscles of the tongue.

  15.   B.   The superior laryngeal nerve (SLN) is a mixed motor and sensory nerve that receives sensory information from the supraglottic larynx and provides motor innervation to the cricothyroid muscle. The cricothyroid muscle tenses and adducts the vocal cords. This action raises the pitch of speech and enables singing. Acute, bilateral denervation of the external branch of the SLN may cause hoarseness and other subtle voice findings. However, the ability to adduct and abduct the vocal cords would remain intact.

  16.   C.   Sensory innervation of the larynx above the vocal cords is carried by fibers of the superior laryngeal nerve (SLN). The internal branch of the SLN provides sensory innervation to the supraglottic portion of the larynx, including all of the epiglottis and the supraglottic mucosa. The external branch of the SLN is primarily a motor nerve that innervates the cricothyroid muscle. The SLN can be blocked as it descends between the greater cornu of the hyoid bone and the superior cornu of the thyroid cartilage. As shown in Figure 2-4, “SLN block” is likely to block the internal branch of the SLN, but not the external “motor” branch. Choice A describes a glossopharyngeal block. Choice B does not describe a clinically relevant procedure (i.e., the injection would be too medial to reliably block the SLN). Choice D describes a transtracheal topicalization of RLN fibers.

  17.   C.   The efferent limb of the glottic closure reflex involved in laryngospasm is primarily mediated by the recurrent laryngeal nerve (RLN), while the afferent limb is mediated by the superior laryngeal nerve (SLN). The RLN innervates all of the muscles of the larynx except the cricothyroid muscle. The external branch of the SLN (not one of the listed options) is a motor nerve that innervates the cricothyroid muscle. The cricothyroid muscle contributes to laryngospasm by lengthening, and thus tensing the vocal cords.

  18.   B.   The presentation of acute aphonia and respiratory distress immediately after thyroidectomy are suggestive of bilateral injury to the recurrent laryngeal nerve (RLN), a recognized complication of this surgery. Bilateral RLN injury leaves the vocal cords tensed and closed due to the unopposed action of the cricothyroid muscles. The cricothyroid muscle is innervated by the external (motor) branch of the superior laryngeal nerve (SLN). Blockade of the motor branch of the SLN should improve the patient’s respiratory distress by relaxing the vocal cords but would have no impact on the aphonia. Practically speaking, a typical “SLN block” (i.e., injection of ∼2 mL of local anesthetic between the greater cornu of the hyoid cartilage and the superior cornu of the thyroid cartilage) is likely to only block the internal (sensory) branch of this nerve as opposed to the motor branch (Fig. 2-4).

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Figure 2-4.  Gross anatomic distribution of the SLN and RLN.

  19.   A.   A cough occurs through the stimulation of a complex reflex arc. This is initiated by the irritation of cough receptors, which are found in the pharynx, larynx, trachea, carina, branching points of large airways, and more distal smaller airways. When triggered, impulses travel via the internal branch of the superior laryngeal nerve and the recurrent laryngeal nerve, which stem from the vagus nerve, to the medulla of the brain. This is the afferent neural pathway. The efferent neural pathway then follows, with relevant signals transmitted back from the cerebral cortex and medulla via the vagus and superior laryngeal nerves to the glottis, external intercostals, diaphragm, and other major inspiratory and expiratory muscles.

  20.   B.   Acute, bilateral injury to the vagus nerve (CN X) terminates all of the motor innervation to the larynx. This leaves the vocal cords in a fully open or abducted position. In contrast, bilateral injury to the recurrent laryngeal nerve (a branch of the vagus) would leave the cords paralyzed in a partially adducted position because of unopposed action of the cricothyroid muscle. This adducted position may cause stridor and respiratory distress, especially if the patient has any concurrent laryngeal edema. Choice A would be observed during laryngospasm. Choice D would be observed in a patient with a normal larynx who is alternating between breathing and phonating.

  21.   C.   Postoperative hoarseness can result from injury to the motor nerves which innervate the larynx. The left recurrent laryngeal nerve (RLN) is particularly vulnerable to injury during cardiothoracic surgeries and many neck surgeries due to its anatomic location. After branching off the left vagus nerve in the chest, the left RLN passes between the left pulmonary artery and the arch of the aorta above before ascending alongside the trachea to the larynx. The right RLN, in contrast, branches off the right vagus nerve in the lower neck where it passes under the root of the right subclavian artery before ascending alongside the trachea to the larynx. An aortic arch repair that spares the arch vessels would be more likely to damage the left RLN than the right RLN.

                Acute injury to the left RLN would leave the left vocal cord subject to the unopposed action of the cricothyroid muscle (the only laryngeal muscle NOT innervated by the RLN). This muscle stretches and tenses the vocal cords, an action that shifts the vocal cords toward midline (adduction). During inspiration, both vocal cords normally abduct, maximizing the glottic opening for air movement. During inspiration, a patient with acute left RLN palsy would be expected to have an adducted left vocal cord and an abducted right vocal cord.

  22.   D.   Above the vocal cords, the sensory innervation of the larynx is via the superior laryngeal nerve. Below the vocal cords, sensory innervation is via branches of the recurrent laryngeal nerve (RLN). The vocal cords themselves receive dual innervation from both nerves. The trigeminal nerve (choice A) provides tactile sensation, among other things, to the anterior two-thirds of the tongue and the nasal passages. The glossopharyngeal nerve (choice B) provides tactile and gustatory sensation to the posterior one-third of the tongue. None of the choices except for the RLN would be stimulated during an awake tracheostomy.

  23.   B.   The ophthalmic (V1) and maxillary (V2) divisions of the trigeminal nerve (CN V) convey sensory information from the nasal mucosa. Blockade of these nerves would facilitate awake nasotracheal intubation. The gag reflex is elicited primarily by tactile stimulation of the posterior one-third of the tongue. The afferent limb of this reflex is carried by the glossopharyngeal nerve (CN IX), not the recurrent laryngeal nerve (choice A) or the hypoglossal nerve (choice D). The superior surface of the epiglottis is innervated by the superior laryngeal nerve (SLN), not the glossopharyngeal (choice C). In general, the SLN provides sensory innervation to all structures of the larynx above the vocal cords, including the epiglottis.

  24.   C.   Both nasotracheal intubation and nasal trumpet insertion are contraindicated in patients with facial or skull injuries (choice A), with coagulopathy (choice B), and those on anticoagulation (choice D). In choice A, the patient’s mechanism of injury and findings of periorbital bruising suggest an underlying skull fracture. In addition to periorbital ecchymoses, other classic signs of a basilar skull fracture include leakage of blood or cerebrospinal fluid from the nares, ecchymoses on the skin overlying the mastoid process, and hemotympanum or bleeding from the ears. For a patient with temporomandibular joint dysfunction who has none of the above contraindications (choice C), the nasal trumpet would be a reasonable way to bypass the patient’s limited mouth opening and relieve upper airway obstruction.

  25.   D.   This patient has multiple risk factors for difficult intubation, including Mallampati class > 2, thyromental distance < 3 fingerbreadths, mouth opening < 3 fingerbreadths, and total atlanto-occipital range-of-motion < 80 degrees. Patients with inflammatory rheumatoid arthritis (RA) have an increased incidence of temporomandibular joint disease (and associated limited mouth opening) and immobile cervical vertebra (associated with limited neck range-of-motion). Additionally, patients with RA can have occult airway abnormalities not apparent on physical exam, such as laryngeal rotation, cricoarytenoid arthritis, and cervical spine instability. The patient’s thyroid malignancy may result in other airway abnormalities including tracheal deviation and/or compression. Were such a patient to be induced and mask ventilation turn out to unsuccessful, there would be no reliable backup method of airway management. The safest way to secure this patient’s airway would be an awake fiberoptic intubation. Since the patient has refused this option and the case is not urgent, the anesthesiologist should cancel the operation and discuss the options for airway management with the patient so that a mutually acceptable plan can be reached.

  26.   B.   The “cannot intubate, cannot ventilate” scenario is an emergency and necessitates immediate invasive airway access to prevent anoxic injury. Two options include transtracheal jet ventilation and surgical cricothyrotomy. Transtracheal jet ventilation requires that the airway be cannulated in some way. In emergent circumstances, this may be accomplished by cannulating the cricothyroid membrane with an intravenous catheter (e.g., 14/16G) and then attaching the end of the catheter to a jet ventilator. Jet ventilation requires a pathway for expired air to egress out of the lungs. Thus, when using transtracheal ventilation, laryngospasm (choice C), or another cause of upper airway obstruction (choice A), would rapidly cause pulmonary overinflation and barotrauma. In contrast, a surgical cricothyrotomy permits both inhalation and exhalation through the lumen of inserted tube (choice B) and so is not dependent on upper airway patency in order to function safely. Transtracheal jet ventilation is a temporary way to provide oxygenation until a definitive airway can be established. With prolonged jet ventilation, the delivered high pressures can expel the catheter out of the trachea. When the catheter migrates into the anterior cervical soft tissues, catastrophic subcutaneous emphysema can rapidly develop rendering other attempts at invasive airway access impossible. Surgical cricothyrotomy, on the other hand, is a definitive method of securing the airway that can be used for up to 72 hours.

  27.   A.   The ASA Difficult Airway Algorithm recommends use of supraglottic devices such as the laryngeal mask airway (LMA) as rescue tools when laryngoscopy and mask ventilation are unsuccessful. Although the patient in choice A ideally would be treated with “full stomach” precautions, if a rapid sequence induction and intubation are unsuccessful, an LMA may be a life-saving tool to oxygenate and ventilate the patient. Aside from its use as a rescue device, the LMA can be used as a supraglottic airway for elective surgery. Relative contraindications to the elective use of the LMA include low airway compliance (choices B and C), incompetence of the gastroesophageal sphincter (choice C), and in patients with a full stomach (choice D).

  28.   D.   “Deep extubation” refers to the technique of removing the endotracheal tube in a patient breathing spontaneously who remains anesthetized such that his or her protective airway reflexes are still abolished. This technique decreases the chance of a patient coughing during emergence in response to the presence of an endotracheal tube. Deep extubation may be performed because of potential benefit related to a patient’s medical comorbidities or for surgical reasons. For example, a patient with coronary artery disease or heart failure may benefit from deep extubation to avoid the sympathetic surge associated with awake extubation and a patient undergoing abdominal hernia repair may benefit from deep extubation to avoid the increased intra-abdominal pressure associated with coughing. However, deep extubation should not be attempted in patients with contraindications to this technique. These include patients with a full stomach (choices A and B) and in patients who may be challenging to mask ventilate or reintubate. Choice C would fall into this latter category because of the potential for airway edema from prolonged prone positioning.

  29.   D.   Mask ventilation can be made difficult by anything that prevents the face mask from forming an adequate seal with the patient’s face (e.g., a beard) or increases the resistance to airflow between the mouth and larynx. Edentulousness, a history of snoring, history of neck radiation, multiple attempts at laryngoscopy, male gender, obesity, and Mallampati status ≥3 are all factors associated with difficult mask ventilation. Choices A, B, and C represent risk factors for difficult intubation. In general, factors that make it difficult to align the oral axis with the laryngeal axis result in difficult intubation. These factors include prominent maxillary teeth, a highly arched or very narrow palate, and an acute angle between the mouth and larynx.

  30.   B.   Flow–volume loops can help differentiate fixed vs. dynamic causes of airway obstruction. They can also help to distinguish extrathoracic vs. intrathoracic sources of the obstruction. During the inspiratory phase of spontaneous ventilation, an extrathoracic obstruction is drawn into the pathway of air movement by subatmospheric intraluminal pressures. In contrast, an intrathoracic obstruction is stented open during inspiration by the negative extraluminal intrathoracic pressure. During expiration in a spontaneously breathing patient, an extrathoracic obstruction is stented open by supra-atmospheric intraluminal pressure. In contrast, an intrathoracic obstruction is exacerbated during expiration, since the extraluminal intrathoracic pressure exceeds the intraluminal pressure. Choice A represents a normal flow–volume loop. Choice C represents a fixed obstruction, that is, one present during both inspiration and expiration. Choice D represents a dynamic intrathoracic obstruction, which would be expected in a patient with asthma or chronic obstructive pulmonary disease.