NAVLE Veterinary Anesthesia and Pain Management 6

Question 1

A 7-year-old intact male Boxer with a known history of dilated cardiomyopathy requires anesthesia for a splenic mass removal. Which induction protocol is MOST appropriate to minimize myocardial depression while providing adequate anesthesia depth?

Accepted Answer

Etomidate 1–2 mg/kg IV with midazolam 0.2 mg/kg IV premedication

Answer

Etomidate is the induction agent of choice in critically ill or cardiovascularly compromised patients because it produces minimal myocardial depression and maintains cardiac output and vascular tone better than propofol or alfaxalone. Midazolam co-induction reduces the etomidate dose needed and provides muscle relaxation without significant cardiovascular effects. Propofol and alfaxalone both cause dose-dependent vasodilation and myocardial depression. Ketamine, while a sympathomimetic, is contraindicated in patients with pre-existing tachyarrhythmias (common in Boxers with DCM) as it can exacerbate ventricular dysrhythmias.

Question 2

During isoflurane anesthesia in a cat undergoing a perineal urethrostomy, end-tidal CO₂ rises to 65 mmHg despite a respiratory rate of 16 breaths/min and tidal volume appearing normal. Oxygen saturation (SpO₂) is 99%. Which is the MOST likely cause?

Accepted Answer

Exhausted CO₂ absorbent in a circle rebreathing system

Answer

Exhausted CO₂ absorbent (e.g., soda lime or barium hydroxide lime that is spent) allows exhaled CO₂ to re-enter the inspiratory limb of a circle breathing system, causing progressive hypercapnia. SpO₂ remains high because oxygen supplementation compensates, making the diagnosis subtle. Esophageal intubation would show absent CO₂ waveform initially or very low ETCO₂, not elevated. Malignant hyperthermia is extremely rare in cats and would present with rapidly escalating hyperthermia, tachycardia, muscle rigidity, and metabolic acidosis—not isolated ETCO₂ elevation. A kinked ETT would reduce tidal volume and cause increased airway pressure, not isolated hypercapnia with normal SpO₂ and visible normal breathing.

Question 3

A 12-year-old horse with recurrent uveitis undergoes a vitrectomy under general anesthesia. Thirty minutes into the procedure, the surgeon reports the eye is extremely firm (increased intraocular pressure). Which anesthetic agent, if used, is MOST likely responsible for this finding?

Accepted Answer

Ketamine administered as a constant rate infusion

Answer

Ketamine elevates intraocular pressure (IOP) by increasing extraocular muscle tone and by inducing nystagmus and blepharospasm, which mechanically compress the globe. This effect is clinically significant in ophthalmic surgery where a firm eye impairs surgical access and can cause expulsive hemorrhage or vitreous prolapse. Alpha-2 agonists like romifidine and medetomidine actually decrease IOP through reduced aqueous humor production and systemic blood pressure, making them preferable adjuncts in ophthalmic cases. Butorphanol has no clinically meaningful effect on IOP. Ketamine CRIs are therefore avoided or used with extreme caution in intraocular surgical procedures.

Question 4

A 35 kg Labrador Retriever is receiving a morphine CRI at 0.1 mg/kg/hr post-orthopedic surgery. Six hours postoperatively, the dog is dysphoric, vocalizing, scratching at the face, and mildly ataxic, with a heart rate of 58 bpm. The MOST appropriate next step is:

Accepted Answer

Administer low-dose naloxone 0.002 mg/kg IV and reassess pain score

Answer

The clinical picture—dysphoria, facial scratching (opioid-induced pruritus), ataxia, and bradycardia—represents morphine-induced side effects rather than undertreated pain. Full reversal with a standard naloxone dose (0.04 mg/kg) would eliminate analgesia, causing acute pain rebound. Low-dose naloxone (0.001–0.004 mg/kg IV) selectively reverses side effects such as dysphoria, pruritus, and excessive sedation while largely preserving analgesic efficacy. Increasing the CRI would worsen the side effect profile. Acepromazine can deepen sedation but does not address the underlying opioid-mediated dysphoria and may mask neurologic deterioration.

Question 5

During anesthesia of a 6-month-old intact female rabbit for an ovariohysterectomy, the patient develops sudden bradycardia (HR 80 bpm, baseline 220 bpm), hypotension (MAP 32 mmHg), and hypothermia (35.1°C) twenty minutes after intubation. Isoflurane vaporizer reads 2.5%. Which intervention takes highest priority?

Accepted Answer

Reduce isoflurane to 1.0–1.5% and initiate active warming

Answer

Rabbits are highly sensitive to isoflurane-induced cardiovascular depression; an end-tidal isoflurane of 2.5% is markedly excessive for this species (typical maintenance is 1.5–2.0% at most). The combined bradycardia, hypotension, and hypothermia in a young rabbit at high isoflurane concentrations most likely represent anesthetic overdose. Reducing the vaporizer immediately is the highest-priority intervention. Active warming addresses hypothermia, which potentiates anesthetic depth and cardiac depression. Atropine may be needed but does not address the root cause (excessive anesthetic depth). Epinephrine is reserved for cardiac arrest. Aggressive fluid loading at 10 mL/kg/hr risks pulmonary edema in a small exotic patient without addressing the overdose.

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE Veterinary Anesthesia and Pain Management 6