NAVLE Veterinary Anesthesia and Pain Management 1 — Questions and Answers
Question 1: Which preanesthetic agent is CONTRAINDICATED in patients with suspected splenic masses because it causes splenic engorgement and sequestration of red blood cells?
- Acepromazine (Correct answer)
- Butorphanol
- Dexmedetomidine
- Midazolam
Correct answer: Acepromazine
Acepromazine (a phenothiazine) causes splenic engorgement by relaxing the splenic capsule, which can significantly enlarge an existing splenic mass and complicate diagnosis or surgery.
Question 2: Among the currently used inhalant anesthetics, which has the LOWEST blood:gas partition coefficient, resulting in the fastest induction and recovery?
- Halothane
- Isoflurane
- Sevoflurane
- Desflurane (Correct answer)
Correct answer: Desflurane
Desflurane has the lowest blood:gas partition coefficient (~0.42), meaning it equilibrates rapidly between blood and alveoli, producing the fastest induction and recovery of the available inhalants.
Question 3: A cat receiving repeated or prolonged propofol infusions is at risk for which unique hematologic complication?
- Thrombocytopenia
- Heinz body anemia (Correct answer)
- Aplastic anemia
- Disseminated intravascular coagulation
Correct answer: Heinz body anemia
Cats lack efficient glucuronidation and are sensitive to the phenolic compounds in propofol, which can cause oxidative damage to hemoglobin and formation of Heinz bodies, leading to hemolytic anemia.
Question 4: Xylazine and dexmedetomidine produce sedation and analgesia through which primary mechanism of action?
- GABA-A receptor potentiation
- Alpha-2 adrenergic receptor agonism (Correct answer)
- Mu-opioid receptor agonism
- NMDA receptor antagonism
Correct answer: Alpha-2 adrenergic receptor agonism
Alpha-2 adrenergic agonists such as xylazine and dexmedetomidine bind presynaptic and postsynaptic alpha-2 receptors in the CNS and periphery, producing dose-dependent sedation, muscle relaxation, and analgesia.
Question 5: Which preanesthetic agent has the LEAST cardiovascular depression and is therefore most appropriate in critically ill or hemodynamically unstable patients?
- Acepromazine
- Medetomidine
- Midazolam (Correct answer)
- Xylazine
Correct answer: Midazolam
Midazolam and other benzodiazepines have minimal cardiovascular effects, making them preferred preanesthetic agents for critically ill, geriatric, or hemodynamically compromised patients.
Question 6: Ketamine is commonly used as an induction agent, particularly in cats. What is its PRIMARY mechanism of anesthetic action?
- GABA-A receptor potentiation
- Alpha-2 adrenergic agonism
- NMDA receptor antagonism (Correct answer)
- Mu-opioid receptor agonism
Correct answer: NMDA receptor antagonism
Ketamine produces dissociative anesthesia primarily by non-competitive antagonism of NMDA (N-methyl-D-aspartate) glutamate receptors, which also contributes to its analgesic properties.
Question 7: Which drug is the specific reversal agent for alpha-2 adrenergic agonist sedation (e.g., medetomidine, dexmedetomidine) in veterinary patients?
- Naloxone
- Flumazenil
- Atipamezole (Correct answer)
- Neostigmine
Correct answer: Atipamezole
Atipamezole is a selective alpha-2 adrenergic antagonist that rapidly reverses the sedation, analgesia, and cardiovascular effects of alpha-2 agonists such as medetomidine and dexmedetomidine.
NAVLE Veterinary Anesthesia and Pain Management 1
Which preanesthetic agent is CONTRAINDICATED in patients with suspected splenic masses because it causes splenic engorgement and sequestration of red blood cells?