Lippincott's Anesthesia Review: 1001 Questions and Answers

Chapter 16. Ophthalmic, Ear, Nose, and Throat Surgery

Thoha Pham

    1.   The most accurate statement regarding absorption of topically administered ophthalmic drugs is that they are absorbed

          A.   Slower than subcutaneous absorption

          B.   Faster that intravenous absorption

          C.   Similar to oral absorption

          D.   Slower than intravenous absorption

    2.   Drainage of aqueous humor occurs at all of these sites, except

          A.   Canal of Schlemm

          B.   Trabecular network

          C.   Episcleral venous system

          D.   Tear ducts

    3.   The normal intraocular pressure (IOP) is _______ (mm Hg):

          A.   5

          B.   10

          C.   25

          D.   30

    4.   Correct consequence of respiratory variables on intraocular pressure (IOP) is

          A.   Decrease in PaO2 will decrease IOP

          B.   Increase in PaO2 will decrease IOP

          C.   Decrease in PaCO2 will increase IOP

          D.   Increase in PaCO2 will increase IOP

    5.   All of the following will serve to decrease intraocular pressure (IOP), except

          A.   Nitrous oxide

          B.   Acidosis

          C.   Morphine

          D.   Vecuronium

    6.   Increases in intraocular pressure (IOP) following succinylcholine administration for tracheal intubation can be minimized by all of the following, except

          A.   β-Adrenergic blocker

          B.   Nondepolarizing relaxant

          C.   Detachment of extraocular muscles from the globe

          D.   Lidocaine

    7.   The ocular effects of ketamine includes

          A.   Pupillary constriction

          B.   Blepharospasm

          C.   Decrease in intraocular pressure

          D.   Myoclonus

    8.   An 82-year-old female patient who resides in a nursing home facility presents for breast biopsy. She states that she uses eye drops to treat glaucoma, but does not know exact names. Patient denies other medical issues, however states that she frequently has acid reflux. Potential anesthetic considerations as a result of eye drops include all of the following, except

          A.   Hyperchloremic metabolic acidosis

          B.   Hypokalemic metabolic acidosis

          C.   Prolonged neuromuscular block with succinylcholine

          D.   Atropine-resistant bradycardia

    9.   An air bubble is injected into the posterior chamber at the conclusion of retinal surgery (pneumatic retinopexy) to facilitate anatomically correct healing. The most appropriate anesthetic management, before the air bubble is injected, is

          A.   Increase depth of anesthesia

          B.   Discontinue nitrous oxide (N2O)

          C.   Ensure adequate muscle relaxation

          D.   Hyperventilate the patient

  10.   Compared with air, sulfur hexafluoride (SF6) bubble injected following vitreous surgery

          A.   Has a longer duration of action

          B.   Is more soluble in blood than nitrogen

          C.   Is inert and will not expand

          D.   Is contraindicated in outpatient surgery

Questions 11 to 14

A 22-month-old 14.5-kg “preemie” is undergoing strabismus repair under general endotracheal anesthetic (GETA). Following an uneventful inhaled induction with sevoflurane, peripheral IV was obtained, and by oversight, patient was given 20 mg of succinylcholine prior to intubation. Masseter spasm was noted moments later.

  11.   What parameter is considered the earliest sign and symptom of an ensuing hypermetabolic state following succinylcholine administration?

          A.   Hyperthermia

          B.   Hypotension

          C.   EtCO2 increase

          D.   Low oxygen saturation

  12.   Midway through the surgery, when surgical traction in the operative field is applied, patient’s heart rate plummets from 110 bpm down to 55 bpm. The pairing that accurately reflects the afferent and efferent limbs, respectively, of this reflex is

          A.   Trigeminal nerve vagus nerve

          B.   Optic nerve vagus nerve

          C.   Vagus nerve trigeminal nerve

          D.   Trochlear Nerve optic nerve

  13.   The most appropriate first step in the management of this hemodynamic instability is

          A.   Epinephrine

          B.   Atropine

          C.   Remove traction

          D.   Phenylephrine

  14.   At the conclusion of the surgery, postoperative nausea and vomiting should be anticipated and can be minimized by all of the following, except

          A.   Serotonin (5-HT3) antagonist

          B.   Propofol infusion

          C.   Limiting opioids

          D.   Deep extubation

  15.   The true statement regarding an oculocardiac reflex is

          A.   It does not occur in enucleated patients

          B.   Incidence is increased in the setting of hypercarbia

          C.   Intensity increases with repeated stimulation

          D.   Suppressed by general anesthesia

  16.   All of the following anatomic structures may participate in triggering an acute and abrupt bradycardia during ophthalmic surgery, except

          A.   Trigeminal nerve

          B.   Vagus nerve

          C.   Globe

          D.   Optic nerve

  17.   Appropriate anesthetic management for ophthalmic surgery requires tight control of intraocular pressure (IOP) before, during, and after the procedure. The accurate effect of an anesthetic drug or maneuver on IOP is

          A.   Decreased by glycopyrrolate

          B.   Increased by hyperventilation

          C.   Decreased by nitrous oxide

          D.   Increased by nondepolarizing muscle relaxants

  18.   All these nerves can be disrupted by injection of local anesthetics into the retrobulbar space, except

          A.   Optic nerve

          B.   Oculomotor nerve

          C.   Trochlear nerve

          D.   Abducens nerve

  19.   The eye movement that is preserved, or unaffected, following a retrobulbar block with 0.5% bupivacaine is

          A.   Abduction

          B.   Rotation

          C.   Adduction

          D.   Elevation

  20.   Possible complications of a retrobulbar block include all the following, except

          A.   Central retinal artery occlusion

          B.   Oculocardiac reflex

          C.   Puncture of the globe

          D.   Horner syndrome

Questions 21 to 22

A patient is given propofol 20 mg intravenously just before placement of a retrobulbar block (0.5% bupivacaine—3 mL) to provide ocular akinesia for ocular surgery.

  21.   As the surgeon attempts to place a lid speculum, the patient squints, preventing adequate placement. Additional blockade of which muscle can provide additional akinesia?

          A.   Orbicularis oculi

          B.   Temporalis

          C.   Zygomaticus minor

          D.   Levator anguli oris

  22.   Moments later, apnea occurs followed by complete loss of consciousness. The most likely etiology to explain this event is

          A.   Subarachnoid injection of local anesthetic

          B.   Effects of propofol

          C.   Oculocardiac reflex

          D.   Intravenous injection of local anesthetic

Questions 23 to 27

A 57-year-old otherwise-healthy male was leaving a dinner party when he was involved in a rollover car accident during which a foreign object became lodged into his right eye. He is taken to the OR for emergent surgical repair of a penetrating wound to his right globe.

  23.   The most appropriate anesthetic plan to consider is

          A.   Retrobulbar block followed by monitored anesthesia care (MAC)

          B.   IV induction of general anesthesia avoiding muscle relaxants

          C.   Rapid-sequence induction of anesthesia using large dose rocuronium

          D.   Secure the airway with an awake fiberoptic intubation

  24.   Anesthetic strategies that can minimize intraocular pressure (IOP) increase and lessen his risk of ocular extrusion include all of the following, except

          A.   Ketamine

          B.   Hyperventilation

          C.   Inhaled volatile agent, 2.0 MAC

          D.   Controlled hypotension

  25.   Fifteen minutes after the start of surgery, while the surgeon is retracting the medial rectus muscle, the patient becomes hypotensive and bradycardic. The first-line therapy to address this cardiovascular derangement is

          A.   Atropine 1 mg IV

          B.   Phenylephrine 100 μg IV

          C.   Ask the surgeon to stop

          D.   Glycopyrrolate 1 mg IV

  26.   The patient’s vital signs normalize and anesthesia is maintained with desflurane and nitrous oxide. Later in the case, conjunctival instillation of a phenylephrine (10%) solution results in immediate escalation of blood pressure from 105/70 to 220/115 mm Hg, while his pulse falls from 86 to 35 bpm. The ECG reveals new onset of ectopic ventricular complexes. The most appropriate treatment option at this time is

          A.   Ask the surgeon to stop

          B.   Administer nitroprusside

          C.   Administer atropine

          D.   Discontinue nitrous oxide

  27.   At the conclusion of the surgery, patient is extubated and brought to the recovery room (PACU) in a stable condition. Thirty minutes later, when he is more awake, he notes unilateral eye discomfort in the nonsurgical eye. He has associated tearing, conjunctivitis, photophobia, and pain, which is worsened with blinking. These eye symptoms are most likely caused by

          A.   Retinal hemorrhage

          B.   Oculogyric crisis

          C.   Angle-closure glaucoma

          D.   Corneal abrasion

  28.   True statement regarding laryngospasm is

          A.   Associated risk of pulmonary edema

          B.   The false vocal cords do not spasm

          C.   Mediated through the recurrent laryngeal nerve

          D.   Increased risk of aspiration

  29.   A patient in the intensive care unit (ICU) with pulmonary failure requires tracheal intubation. Compared with nasotracheal intubation, oral tracheal intubation carries a higher incidence of

          A.   Patient discomfort

          B.   Maxillary sinusitis

          C.   Transient bacteremia

          D.   Otitis media

  30.   When compared to an adult, the airway anatomy of a 6-week-old infant reveals

          A.   Tongue is smaller and floppy

          B.   Airway is narrowest at the glottic opening

          C.   Position of the larynx is more anterior in the neck

          D.   Epiglottis is flat and firm

Questions 31 to 32

A 3-year-old patient arrives for rescheduled tonsillectomy and adenoidectomy with another acute upper respiratory tract infection (URI). Her initial surgery was postponed 3 weeks ago as she had a URI at that time as well. Exam reveals a runny nose with greenish-yellow discharge with an intermittant wet cough. She is afebrile with normal vital signs.

  31.   Postponement of surgery will reduce the risk of

          A.   Laryngospasm

          B.   Hemorrhage

          C.   Difficult intubation

          D.   Gastroesophageal reflux

  32.   Surgery proceeded without incident; however, 2 hours later in the recovery room (PACU), she vomits a large blood clot followed by ongoing bleeding. She appears pale and anxious. Vitals reveal heart rate = 130 bpm, respiratory rate = 25 bpm, and blood pressure = 77/35 mm Hg. Her capillary refill time is 4 seconds. The most appropriate next step in management at this time is

          A.   Insertion of orogastric tube to empty the stomach of blood

          B.   Emergent return to the operating room

          C.   Administer anxiolysis medication

          D.   Provide liberal fluid resuscitation

Questions 33 to 35

A 65-year-old male requires transoral laser microsurgery to address his laryngeal webs. His medical history reveals remote tobacco smoking and recreational drug use in college.

  33.   Minimizing airway fire hazards associated with laser surgery can be accomplished by use of all of the following, except

          A.   Intermittent mode laser emissions

          B.   An air/oxygen anesthetic technique

          C.   A polyvinylchloride (PVC) endotracheal tube

          D.   Saline-soaked sponges over exposed tissues

  34.   Ten minutes later, the surgeon yells “FIRE!” The most appropriate next step is to

          A.   Ventilate with air

          B.   Increase Fio2 to 1.0

          C.   Instill saline down the endotracheal tube lumen

          D.   Remove the endotracheal tube

  35.   One hour later while recovering in the PACU, the patient is noted to have stridor and difficulty breathing. At this time, the most appropriate next step in his airway management includes

          A.   Administration of aerosolized epinephrine

          B.   Endotracheal intubation

          C.   Administration of helium and oxygen

          D.   Intravenous injection of dexamethasone

  36.   A 10-year-old girl with hoarseness presents for laser microsurgery to address laryngeal papillomas. She is otherwise healthy. The surgeon is requesting a general endotracheal anesthetic (GETA). The gas mixture least likely to support combustion is

          A.   Oxygen 35%, air 65%

          B.   Oxygen 30%, helium 70%

          C.   Oxygen 20%, nitrous oxide (N2O) 80%

          D.   Oxygen 30%, nitrogen (N2) 70%

  37.   A 55-year-old woman with a 35 pack-year history of tobacco smoking is undergoing laryngobronchoscopy utilizing the Sanders jet ventilation technique. The principle behind apneic oxygenation is

          A.   Contrasting density of inhaled gases

          B.   Maintenance of spontaneous ventilation

          C.   Air entrainment

          D.   Use of helium–oxygen mixtures

  38.   During apneic oxygenation via a rigid bronchoscope, anesthetic considerations include all of the following, except

          A.   Duration of the procedure is limited by the increase in carbon dioxide

          B.   Denitrogenation should be performed prior to apnea

          C.   PaCO2 remains unchanged for the first 15 minutes

          D.   Functional residual capacity and body weight influence the rate of desaturation

Questions 39 to 43

A 35-year-old male with a toxic multinodular goiter presents for thyroidectomy with radical neck dissection. He denies any other significant medical history. Review of systems reveals orthopnea and dysphagia with a recent change in the caliber of his voice.

  39.   True statements about this patient include all of the following, except

          A.   A flow–volume loop on spirometry can evaluate tracheal compression

          B.   The airway may obstruct with sedation

          C.   The trachea may collapse postoperatively

          D.   An abnormally low forced expiratory volume in 1 second (FEV1) would be diagnostic of an upper airway obstruction

  40.   To attenuate risk of a “cannot ventilate, cannot intubate” scenario, an awake airway intubation is discussed. The neural structure that does not need to be blocked in order to provide adequate airway analgesia for a nasal intubation is

          A.   Hypoglossal nerve

          B.   Sphenopalatine ganglion

          C.   Superior laryngeal nerve

          D.   Recurrent laryngeal nerve

  41.   At the conclusion of a complicated 4-hour resection, the patient is extubated and brought to the recovery room. One hour after extubation, the patient complains of dyspnea with stridorous respiration. Initial steps include all of the following, except

          A.   Intravenous administration of calcium

          B.   Nebulized racemic epinephrine

          C.   Inspection of the surgical site

          D.   Direct laryngoscopy

  42.   If bilateral recurrent laryngeal nerves were unintentionally severed, the likely finding on direct laryngoscopy would be

          A.   Paralysis of the cricothyroid muscles

          B.   Intermediate position of the cords

          C.   Midline, closed position of the cords

          D.   Pure adductor vocal cord paralysis

  43.   Instead, postoperative direct laryngoscopy reveals normal position of the cords at rest, widely open glottic opening at maximal inspiration, and symmetrically moving cords during quiet breathing but with weak phonation and inability to speak loudly or shout. The most likely etiology is

          A.   Recurrent laryngeal nerve paralysis

          B.   Superior laryngeal nerve (SLN) paralysis

          C.   External airway compression

          D.   Vagus nerve paralysis

Questions 44 to 45

A 27-year-old male arrives to the operating room with laryngotracheal injuries stemming from a motorcycle collision. He presents with hoarseness and dyspnea while sitting, but is unable to lie flat due to worsening dyspnea. He is unable to swallow, and is drooling/spitting moderately blood-stained sputum. His anterior neck is diffusely swollen and exquisitely tender with notable subcutaneous emphysema. Oxygen saturation is 100% with supplemental oxygen via face mask. Review of imaging reveals a thyroid cartilage fracture horizontally and crossing the midline.

  44.   The most appropriate approach to his airway management is

          A.   Tracheostomy

          B.   Laryngeal mask airway

          C.   Nasotracheal intubation

          D.   Cricothyroidotomy

  45.   His injury would be consistent with trauma to this zone of his neck:

          A.   Zone I

          B.   Zone II

          C.   Zone III

          D.   Zone IV

Questions 46 to 47

During thyroidectomy for carcinoma, a 22-year-old patient develops tachycardia to 115 bpm while blood pressure intensifies to 145/100 mm Hg. The inhaled anesthetic is deepened and minute ventilation is increased. Thirty minutes later, tachycardia and hypertension persists despite all efforts (Table 16-1).

Table 16-1

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  46.   The appropriate treatment to consider at this time is

          A.   Propranolol

          B.   Acetaminophen

          C.   Iodine

          D.   Dantrolene

  47.   Diagnosis of malignant hyperthermia is most commonly confirmed by

          A.   Caffeine halothane contracture test (CHCT)

          B.   Urinalysis

          C.   Arterial blood gas

          D.   Core temperature >42°C

CHAPTER 16 ANSWERS

    1.   D.      Topically applied drops are quickly absorbed by the mucosal lining of the nasolacrimal duct as well as by blood vessels in the conjunctival sac with a potential to produce systemic effects. Absorption is rapid, faster than oral or subcutaneous administration, but still slower than intravenous.

    2.   D.      Intraocular pressure (IOP) is a reflection of the eye’s ability to form and drain aqueous humor. The posterior chamber’s ciliary body is the major producer of aqueous humor. Obstruction of the drainage system, whether it is at the canal of Schlemm, the trabecular network, or the episcleral venous system, will elevate IOP. Tear ducts do not contribute to the drainage of aqueous humor.

    3.   B.      Normally, IOP of the eye varies between 10 and 22 mm Hg, and is generally considered abnormal when >25 mm Hg. This pressure is not static, as it can vary by 1 to 2 mm Hg with each cardiac contraction. Diurnal variations of up to 5 mm Hg also exist, with a higher pressure noted upon awakening.

    4.   D.      Hypoventilation (↑PaCO2) along with hypoxemia (↓PaO2) will result in increased IOP, whereas hyperventilation (↓PaCO2) will serve to minimize choroidal blood flow to decrease IOP. Hyperoxemia (↑PaO2) does not affect IOP significantly.

    5.   B.      Inhaled and injected anesthetics (with the exception of ketamine) along with opioids tend to lower IOP. Nondepolarizing muscle relaxants will decrease IOP, presumably via their relaxant effects on extraocular muscles. Hypoventilation (↑PaCO2) results in respiratory acidosis, which will increase IOP (Table 16-2).

Table 16-2  Factors Affecting Intraocular Pressure (IOP)

Increased IOP

 •   Hypertension (sympathetic stimulation) as occurs during laryngoscopy and intubation

 •   Acidosis

 •   Hypoxia

 •   Increased central venous pressure (coughing, valsalva maneuver)

Decreased IOP

 •   Hypotension

 •   Inhalational anesthetics (volatile and nitrous oxide)

 •   Opioids

 •   Nondepolarizing muscle relaxants

Table 16-3  Signs of Malignant Hyperthermia

Early

Late

Increased EtCO2

Hyperthermia

Tachycardia

Elevated creatine phosphokinase

Skeletal muscle spasm/rigidity

Myoglobinuria

Tachypnea

Cyanosis

Sweating

Disseminated intravascular coagulation

Acidosis—respiratory and metabolic

Cardiac arrest

    6.   C.      The use of succinylcholine for eye surgery is controversial. Succinylcholine can increase IOP by about 5 to 10 mm Hg for about 5 to 10 minutes after intravenous administration (longer duration of ↑IOP following intramuscular administration). Pretreatment with nondepolarizing muscle relaxants, lidocaine, or β-blockers may reduce the ocular hypertensive response to minimize increases in IOP. The increase in IOP after succinylcholine persists whether or not the extraocular muscles are intact, suggesting that cycloplegic effects, rather than physical contraction, are responsible for IOP elevation.

    7.   B.      Ketamine may cause nystagmus and blepharospasm and may not be suitable for ophthalmic surgery. Studies with respect to the effect of ketamine on intraocular pressure (IOP) have shown conflicting results, but it appears more likely to increase, as opposed to decrease, ocular pressures. This may depend on whether ketamine is administered through the IM or IV route. Ketamine is not known to affect pupil size. Myoclonus is commonly associated with etomidate and likely should also be avoided when IOP control is essential.

    8.   A.      Topical ophthalmic medications undergo sufficient and prompt absorption to produce systemic effects and may cause adverse cross-reactions to medications used in routine anesthesia care. Acetazolamide drops, due to its action as a carbonic anhydrase inhibitor, can induce a hypokalemic metabolic acidosis. Topical echothiophate iodine, an irreversible cholinesterase inhibitor, can reduce plasma cholinesterase activity, prolonging the duration of action of succinylcholine and mivacurium. Absorption of timolol, a nonselective β-adrenergic blocker has been associated with atropine-resistant bradycardia, hypotension, and bronchospasm during general anesthesia. Hyperchloremic acidosis is largely related to large volume resuscitation with normal saline.

    9.   B.      In the presence of N2O, air bubbles will increase in size as N2O is 35 times more soluble compared to molecular nitrogen (the major component of air), allowing it to diffuse into an air bubble more rapidly than nitrogen is absorbed out of the bubble. If the bubble expands after the incision is closed, intraocular pressure will rise. This complication can be avoided by discontinuing N2O at least 15 minutes prior to the bubble injection, as the washout of N2O from the lungs is 90% complete within 10 minutes. Additionally, repeat general anesthesia with N2O should be avoided until the bubble is fully absorbed, which for air can take up to 5 days.

  10.   A.   SF6 is an inert gas that is much less soluble than nitrogen (the major component of air) in blood and, therefore, will have a longer duration of action (10 days) compared to an air bubble. Bubble size doubles within 24 hours after injection of SF6 because nitrogen from inhaled air will enter more rapidly into the bubble than sulfur can diffuse out of it. This slow bubble expansion usually does not pathologically affect IOP. However, inspired N2O, which is 117 times more diffusible than hexafluoride (compared to 35 times more than nitrogen), will rapidly enter the SF6 bubble such that IOP will rise significantly within 30 minutes after the eye is closed. As with air, repeat general anesthesia with N2O should be avoided until the SF6 bubble is fully resorbed.

  11.   C.   Although still quite rare, an increased incidence of malignant hyperthermia (MH) has been reported in patients with strabismus (underlying myopathy) such that a high index of suspicion should be maintained. EtCO2 is considered the earliest indicator of a hypermetabolic state with unexpected increases in CO2 despite constant minute ventilation. Avoiding known triggers can negate the risk of inducing MH, such that succinylcholine is not recommended during strabismus surgery involving infants and children.

  12.   A.   Trigeminovagal reflex: the afferent limb of the oculocardiac reflex is via the trigeminal nerve (CN V), primarily through the ophthalmic division (V1). The impulse travels along the long and short ciliary nerves (LCN and SCN) to synapse on the ciliary ganglion. The impulse then continues through the trigeminal ganglion arriving at the sensory nucleus of the trigeminal nerve. The convergence between the afferent and efferent limbs is at the motor nucleus of the vagus nerve (CN X) of the brain stem. From here, the efferent limb is via the vagus nerve, which eventually synapses on the sinoatrial node of the heart, resulting in an abrupt bradycardia (Fig 16-1).

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Figure 16-1.

  13.   C.   The oculocardiac reflex (OCR) occurs frequently during strabismus surgery. It can occur following traction of the extrinsic eye muscles, or placement of pressure on the globe. The OCR is most commonly manifested as bradycardia, which regresses almost immediately after the stimulus is removed. Bigeminy, ectopy, nodal rhythms, atrioventricular block, and cardiac arrest have also occurred. Traction on any of the extraocular muscles can evoke this reflex, but it appears that manipulation of the medial rectus muscle is the most consistent trigger. Though the prophylactic use of an anticholinergic (atropine or glycopyrrolate) before the potential evoking stimulus may be recommended, the most effective treatment is the removal of the stimulus.

  14.   D.   The incidence of nausea and vomiting following strabismus surgery can be high, ranging anywhere from 48% to 85%. Minimizing the use of opioids, substituting propofol for inhaled anesthetics, along with the prophylactic use of antiemetics can reduce nausea and vomiting after surgery. Deep extubation has no impact on postoperative nausea and vomiting, and may place patient at risk for aspiration.

  15.   B.   The afferent limb of the oculocardiac reflex (OCR) is the trigeminal nerve such that pressures on the globe, conjunctiva, or orbital structures and traction on the extraocular muscles are potential triggers. This reflex occurs even with an empty globe. Hypercarbia and hypoxemia are factors believed to augment the incidence and severity of the reflex. This reflex is noted to fatigue with repeated stimulation and is not suppressed by general anesthesia.

  16.   D.   The afferent limb of the oculocardiac reflex is the trigeminal nerve such that triggers include pressure on the globe, conjunctiva, or orbital structures as well as traction of the extraocular muscles. The vagus nerve is the efferent limb with connections to the sinoatrial node triggering a reflex bradycardia. The optic nerve is not involved in this reflex activity.

  17.   C.   Anticholinergics (e.g., glycopyrrolate) may include mydriasis of the pupils, leading to an increase in intraocular pressure. Unlike atropine, however, glycopyrrolate is completely ionized at physiologic pH; thus, the occurrence of CNS-related side effects is lower, as it has difficulty crossing the blood–brain barrier. Anesthetic agents, whether inhaled or injected, reduce IOP, with the possible exception of ketamine. Nondepolarizing neuromuscular-blocking agents produce a slight decrease, while depolarizing relaxants increase IOP. Hyperventilation will cause vasoconstriction with decrease in choroidal blood flow and intraocular pressures.

  18.   C.   Nerves blocked are those within the optic cone (annulus of Zinn), which include optic (CN II), oculomotor (CN III), and the abducens (CN VI). The trochlear nerve (CN IV) is not affected, since it is located outside of this muscle cone.

  19.   B.   The trochlear nerve (CN IV) remains intact following a retrobulbar block, since it is located outside of the muscle cone. The trochlear nerve innervates the superior oblique muscle; thus, rotational movement of the eye remains intact.

  20.   D.   Common complications attributed to a retrobulbar block include retrobulbar hemorrhage with possible central artery occlusion, oculocardiac reflex, puncture of the posterior globe, penetration of the optic nerve, and inadvertent intrathecal injection. Horner syndrome is not commonly seen following retrobulbar blocks; instead, it results from an interruption of the sympathetic nerve supply to the head/face, resulting in a triad of miosis, ptosis, and anhidrosis.

  21.   A.   Blockade of the orbicularis oculi muscle, which is a sphincter muscle around the eye, can further provide adequate surgical conditions for any ocular procedure with consequent inability to squeeze the lids shut. This can be achieved by blockade of the facial nerve (CN VII).

  22.   A.   There is 1% to 3% risk of complications with retrobulbar block, ranging from mild to severe. Possible complications include accidental subarachnoid injection, which can cause a “total spinal” leading to apnea, unconsciousness, and cardiorespiratory collapse.

  23.   C.   Eye injuries commonly occur as a result of trauma, which frequently means providing emergent general anesthesia for patients with full stomachs. It is important to avoid any sudden increases in intraocular pressure (IOP) that may cause extrusion of the ocular contents. Although awake tracheal intubation provides the greatest margin of safety to prevent aspiration, it may in fact promote increase in IOP with inadequate orotracheal anesthesia. Placement of a retrobulbar block is not advised as inadvertent globe puncture may lead to extrusion of orbital contents. For most cases, rapid-sequence or modified rapid-sequence induction is utilized. The choice of succinylcholine offers the advantage of rapid onset of muscle relaxation, but may acutely cause elevation in IOP. Alternatively, the use of a large dose of nondepolarizing neuromuscular-blocking agent will reduce IOP and facilitate tracheal intubation as long as adequate blockade is confirmed prior to laryngoscopy.

  24.   A.   Hyperventilation, hypotension, and hypothermia decrease IOP, whereas arterial hypoxemia and hypoventilation elevate IOP. External pressure can also be generated by venous congestion of orbital veins, which is accentuated during a valsalva, coughing, and vomiting. Additionally, most inhaled and injected anesthetics (with the exception of ketamine) can also serve to reduce IOP.

  25.   C.   The oculocardiac reflex best explains this cardiovascular presentation during ophthalmologic surgeries. First-line therapy is always to remove the stimulus, which is mediated via trigeminal afferents.

  26.   B.   Hypertensive episodes during anesthesia should be tackled logically. Common causes are light anesthesia, hypoxia, and hypercarbia. In this case, excessive systemic uptake of the phenylephrine precipitated severe hypertension. Elevated diastolic pressures with ECG pathology necessitate immediate action to prevent further cardiovascular decline. Administration of sodium nitroprusside is beneficial to quickly reduce the blood pressure and decrease cardiac afterload.

  27.   D.   Corneal abrasions produce a foreign body sensation with associated tearing, conjunctivitis, and photophobia. This pain is made worse by blinking. Protection against this occurrence includes application of nonionic petroleum-based ophthalmic ointment to the eye, securely taping the eyelids shut during anesthesia, and discouraging patients from rubbing their eye on emergence. Abrasions can be diagnosed by fluorescein staining, and treatment options include saline flushes, antibiotic ointment, and patching the eye.

  28.   A.   Laryngospasm can complicate any routine airway management and is especially prevalent around the time of extubation. It often occurs during stage 2—“excitement stage”—of general anesthesia in combination with an airway irritant such as blood, mucus, laryngoscope blade, suction catheter, surgical debris, or other foreign objects. This protective reflex is mediated by the superior laryngeal nerve and manifested as sustained closure of the glottis. Laryngospasm with complete airway obstruction can be associated with negative pressure pulmonary edema, as patients can create a significant amount of negative intrathoracic pressure during attempts to breathe against an obstructed upper airway. The management consists of positive pressure ventilation, increasing the depth of anesthesia, and occasionally a small dose of a muscle relaxant with or without reintubation.

  29.   A.   Tracheal intubation to facilitate mechanical ventilation is common in ICU patients to appropriately manage failure of adequate spontaneous ventilation and/or oxygenation. Both nasal and oral tracheal tubes are relatively safe, for at least several weeks, while patients convalesce. When compared with prolonged oral intubation, nasotracheal intubation may be more comfortable for the patient, more secure (fewer occurrences of accidental self-extubations), and less likely to cause laryngeal damage. Nasal intubation, however, has its own significant adverse events, including significant nasal bleeding, transient bacteremia, sinusitis, and otitis media (from obstruction of the auditory tubes).

  30.   C.   Recognizing the anatomical differences between an adult and a pediatric airway is important. One of the most obvious differences is the tongue itself. The pediatric tongue is larger, in relation to the amount of free space in the oropharynx, when compared to the adult tongue. With regards to the pediatric epiglottis, it tends to be large and floppy with a more oblong configuration, making epiglottis control with a laryngoscope blade more challenging. Additionally, the position of the adult larynx is at about the level C5–C6; the pediatric larynx is more cephalad, at about the level of the C3–C4. This is an important anatomical airway consideration, since the higher larynx tends to be more anterior as well (Fig 16-2).

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Figure 16-2.

  31.   A.   Laryngospasm associated with airway manipulation is more likely to occur in the presence of a URI such that surgery is typically postponed until resolution of symptoms, typically 1 to 2 weeks. Young children, however, have frequent URIs such that risk:benefit ratio should be considered when determining appropriateness of proceeding versus further postponement.

  32.   D.   Hemorrhage from a bleeding tonsillar bed in the postoperative period is a hazardous complication. Her vitals reveal hypovolemia and as such, initial management should be to resuscitate the patient prior to returning to the operating room to minimize morbidity associated with anemia and hypovolemia in the setting of repeat general anesthesia. Also assume that patient will now have a difficult airway with a “full stomach.”

  33.   C.   Anesthesia during laser surgery may be administered with or without an endotracheal tube. If intubation is needed, appropriate laser-resistant endotracheal tubes should be utilized. In this regard, remember that all PVC tubes are flammable and can ignite when contacted by the laser beam. Using the laser intermittently, ventilating the patient with a low concentration of combustible gases, along with protecting adjacent tissues with saline-soaked sponges are all appropriate approaches to minimize the fire hazards.

  34.   D.   Airway fires are an inherent risk with laser surgery, such that a plan of action should be considered before the case begins. The cuff of the endotracheal tube may be filled with saline, as opposed to air, to minimize flammability should the laser beam rupture the cuff. Inspired oxygen concentration is minimized as tolerated (usually Fio2 of <0.50), as oxygen readily supports combustion. In the event of an airway fire, the anesthesia circuit should be immediately disconnected to interrupt further delivery of oxygen, followed by removal of the tube from the patient’s airway. If the flame persists, the field should next be flooded with normal saline.

  35.   B.   Post airway fires, it is most appropriate to leave the patient intubated for continued observation as the presence of laryngeal and pharyngeal edema can result in failed extubation. Therefore, this patient should be reintubated with a regular endotracheal tube and monitored for the next 24 hours. Corticosteroids can be considered for severe edema with absent cuff leak, but generally is not given prophylactically.

  36.   B.   The mixture of gases delivered into the endotracheal tube may affect the risk of combustion during general anesthesia and laser surgery of the airway. N2O is highly combustible and should be strictly avoided. Fio2 should be reduced to as low as possible with an air–oxygen mixture. Helium, if available, is ideal as it is inert and noncombustible. Though N2 is also considered safe, the mean time to ignition with nitrogen has been found to be significantly shorter when compared to the same concentration of helium.

  37.   C.   In 1960s, Sanders described ventilation technique using a 16-gauge jet placed down the side arm of a rigid bronchoscope, relying on air entrapment to continue oxygenation with an open bronchoscope. An intermittent jet of oxygen administered from a high-pressure source (50 psi) entrains room air to maintain supranormal oxygen concentrations in the upper airways, which creates a diffusion gradient to the alveolar spaces. This gradient is maintained as alveolar oxygen is constantly consumed.

  38.   C.   Apneic oxygenation relies on mass movement oxygenation. With the onset of apnea, a low pressure develops in the airspace of the lungs, as more oxygen is absorbed (230 mL/min) than CO2 is released (200 mL/min). If the airways are open, 100% oxygen supplied to the upper airways will follow the pressure gradient and flow into the lungs, replacing the oxygen consumed. The uptake of oxygen into the blood will then remain at relatively normal levels, recognizing that the lack of ventilation will eventually cause marked hypercapnia and acidosis.

  39.   D.   The configuration of the flow–volume curve during spirometry testing can be used to demonstrate abnormalities of the larger central airways (larynx, trachea, and main stem bronchi). The FEV1/FVC ratio can provide diagnostic value, as disproportionate reduction in the FEV1 as compared to the FVC is the hallmark of obstructive lung diseases. Concern should be made regarding airway collapse following sedation or induction of anesthesia when extrathoracic lesions are present. If long-standing, tracheomalacia may leave the trachea weak and collapsible postoperatively (Fig 16-3).

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Figure 16-3.

  40.   A.   Anesthesia of the nasal mucosa and nasopharynx is achieved via blockade of trigeminal branches, particularly the sphenopalatine ganglion and ethmoid nerves. Blockade of the glossopharyngeal and superior laryngeal nerves provide anesthesia to the mouth, oropharynx, and base of the tongue. The hypopharynx, larynx, and trachea are innervated via a branch of the vagus nerve (CN X), specifically the recurrent laryngeal nerve, which can be blocked via a transtracheal approach. On the other hand, blockade of the hypoglossal nerve (CN XII) will only serve to paralyze the intrinsic muscles of the tongue without adding to anesthesia of the airway (Fig 16-4).

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Figure 16-4.

  41.   A.   Inspection of the neck is generally considered the first step, as it may reveal a life-threatening and reversible cause of airway obstruction such as a compressing hematoma. Direct visualization of vocal cords may point toward recurrent laryngeal nerve damage contributing to dyspnea. Though hypocalcemia due to removal of the parathyroid glands can occur, signs and symptoms will usually present much later in the perioperative course (24–96 hours), and unlikely to be contributing to dyspnea in the PACU. Inhaled racemic epinephrine is commonly used when stridor is present after extubation.

  42.   B.   The recurrent laryngeal nerves provide motor innervation to all the intrinsic muscles of the larynx, except the cricothyroid muscle, which is innervated by the superior laryngeal nerve. Damage to bilateral recurrent laryngeal nerves will affect abduction and adduction of the cords, resulting in both vocal cords adopting an intermediate, or paramedian, position. Patient would also have associated aphonia with risk of airway obstruction with inspiration as the cords flap together. Unilateral damage will present with hoarseness.

  43.   B.   In the case of lesions to the SLNs, adduction and abduction of the vocal cords remain intact. SLN lesions instead lead to weak tensor strength (cricothyroid muscle), leaving the voice hoarse, weak, breathy, and with the inability to scream or shout. Other associated findings would be loss of sensation above the cords, leaving patient vulnerable to inhalation of any material present in the pharynx.

  44.   A.   Blunt-neck trauma is most commonly a result of a motor vehicle collision associated with rapid acceleration or deceleration injuries, which may include crushing injuries of the trachea, esophagus, vascular structures, and cervical spine. A laryngeal fracture can lead to life-threatening airway obstruction and as such should be treated in an emergent manner. Signs and symptoms of dyspnea, emphysema, and inability to lie flat reflect a fragile airway. Definitive airway management following airway trauma is a surgical airway, most commonly a tracheostomy. Cricothyroidotomy is not recommended following laryngotracheal injuries, as the landmarks are usually difficult to assess, since the cricoid is often the level of the injury.

  45.   B.   The neck is divided into three zones: zone I, including the thoracic inlet, up to the level of the cricothyroid membrane, is treated as an upper thoracic injury. Zone III, above the angle of the mandible, is treated as a head injury. In this case, fracture of the thyroid cartilage represents an injury of the neck in zone II. For ease of memory, consider that the cricoid cartilage demarcates the border between zones I and II and the angle of the mandible separates zone II from zone III (Fig 16-5).

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Figure 16-5.

  46.   D.   Increasing EtCO2 and temperature may reveal possible malignant hyperthermia. With onset of cardiac arrhythmias, and the increasing likelihood of the development of malignant hyperthermia with rapidly climbing EtCO2and hyperthermia, treatment with dantrolene should be considered and pursued. Other signs that can strengthen the diagnosis are muscle rigidity and myoglobinuria.

  47.   A.   More than 30 different mutations are linked to malignant hyperthermia susceptibility. Genetic testing is available to establish a diagnosis, but the CHCT remains the criterion standard.