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
A. Contrasting density of inhaled gases
B. Maintenance of spontaneous ventilation
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
remains unchanged for the first 15 minutes
D. Functional residual capacity and body weight influence the rate of desaturation
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
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
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
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
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
fracture horizontally and crossing the midline.
44. The most appropriate approach to his airway management is
45. His injury would be consistent with trauma to this zone of his neck:
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).
46. The appropriate treatment to consider at this time is
47. Diagnosis of malignant hyperthermia is most commonly confirmed by
A. Caffeine halothane contracture test (CHCT)
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.
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
) results in respiratory acidosis, which will increase IOP (Table 16-2).
Table 16-2 Factors Affecting Intraocular Pressure (IOP)
• Hypertension (sympathetic stimulation) as occurs during laryngoscopy and
• Increased central venous pressure (coughing, valsalva maneuver)
• Inhalational anesthetics (volatile and nitrous oxide)
• Nondepolarizing muscle relaxants
Table 16-3 Signs of Malignant Hyperthermia
Tachycardia Elevated creatine phosphokinase
Skeletal muscle spasm/rigidity Myoglobinuria
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.
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
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
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,
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
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
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
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,
Comments
Post a Comment
اكتب تعليق حول الموضوع