DVM Doctor of Veterinary Medicine Anesthesia and Pain Management Questions and Answers — Questions and Answers
Question 1: A 7-year-old cat with a known history of hypertrophic cardiomyopathy (HCM) requires anesthesia for a full-mouth dental extraction. Which of the following induction agents should be used with the most caution due to its sympathomimetic effects, which increase heart rate and myocardial oxygen demand?
- Propofol
- Alfaxalone
- Ketamine (Correct answer)
- Etomidate
Correct answer: Ketamine
Ketamine is a dissociative anesthetic that causes catecholamine release, leading to increased heart rate, blood pressure, and cardiac output. In a cat with HCM, where the ventricular muscle is thickened and diastolic function is impaired, this increased myocardial oxygen demand can be detrimental and may lead to arrhythmias or cardiac decompensation. Alfaxalone, propofol, and etomidate generally have less impact on heart rate or may cause a decrease, making them safer choices in this scenario.
Question 2: During the anesthesia of an intubated dog, the end-tidal CO2 (ETCO2) reading on the capnograph abruptly drops from a stable 40 mmHg to near 0 mmHg. The waveform is completely lost. Which of the following is the most likely cause?
- Severe hypotension
- Malignant hyperthermia
- Exhausted CO2 absorbent
- Disconnection of the breathing circuit (Correct answer)
Correct answer: Disconnection of the breathing circuit
A sudden drop of the ETCO2 reading and loss of the waveform to near zero indicates a complete failure to sample expired gas from the patient's lungs. The most common cause for this is a mechanical issue like the breathing circuit becoming disconnected from the endotracheal tube, or an accidental extubation. Severe hypotension or cardiac arrest would cause a rapid but not instantaneous drop, while exhausted CO2 absorbent would cause a rise in inspired CO2, and malignant hyperthermia would cause a rapid rise in ETCO2.
Question 3: Which of the following analgesic agents provides pain relief primarily by acting as an N-methyl-D-aspartate (NMDA) receptor antagonist, making it particularly useful for preventing central sensitization or 'wind-up' pain?
- Morphine
- Ketamine (Correct answer)
- Meloxicam
- Dexmedetomidine
Correct answer: Ketamine
Ketamine is a non-competitive NMDA receptor antagonist. This mechanism is crucial for preventing and treating central sensitization ('wind-up'), a state of hyperexcitability in the spinal cord that leads to exaggerated pain responses. Morphine is a mu-opioid agonist, meloxicam is a non-steroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase, and dexmedetomidine is an alpha-2 adrenergic agonist.
Question 4: To perform a complete mandibular nerve block that desensitizes all teeth in the right mandible (quadrant 400) of a dog, where is the most appropriate anatomical target for local anesthetic deposition?
- The mental foramen, located rostrally below the second premolar
- The infraorbital foramen, located rostral to the orbit
- The mandibular foramen, located on the medial surface of the caudal mandible (Correct answer)
- The major palatine foramen, located on the hard palate
Correct answer: The mandibular foramen, located on the medial surface of the caudal mandible
A complete mandibular nerve block requires depositing local anesthetic at the mandibular foramen, where the inferior alveolar nerve enters the mandibular canal. This location, found on the medial (lingual) surface of the caudal mandible (ramus), will desensitize the entire quadrant, including all molars, premolars, the canine, and incisors. Blocking the mental foramen only affects the rostral structures. The infraorbital and major palatine foramina are associated with maxillary (upper jaw) blocks.
Question 5: What is the primary metabolic reason that most non-steroidal anti-inflammatory drugs (NSAIDs) must be used with extreme caution and at specific, validated doses and intervals in cats?
- They are highly susceptible to NSAID-induced hepatotoxicity.
- They frequently develop severe gastric ulceration after a single dose.
- They have a relative deficiency in the hepatic enzyme glucuronyl transferase. (Correct answer)
- They are unable to produce protective prostaglandins in the stomach.
Correct answer: They have a relative deficiency in the hepatic enzyme glucuronyl transferase.
Cats have a relative deficiency in the hepatic enzyme UDP-glucuronosyltransferase (UGT), which is essential for glucuronidation, a major pathway for metabolizing and eliminating many drugs, including most NSAIDs. This metabolic difference results in a significantly prolonged drug half-life, increasing the risk of accumulation and toxicity (especially renal and gastrointestinal) if dosing is not appropriate.
Question 6: A 3-year-old Golden Retriever is recovering 12 hours after a tibial-plateau-leveling osteotomy (TPLO). The patient is receiving a constant rate infusion of fentanyl. To implement a multimodal analgesic plan and target a different part of the pain pathway, which of the following would be the most appropriate class of drug to add?
- An NMDA receptor antagonist, such as ketamine
- A different pure mu-opioid, such as hydromorphone
- An opioid antagonist, such as naloxone
- A non-steroidal anti-inflammatory drug (NSAID), such as carprofen (Correct answer)
Correct answer: A non-steroidal anti-inflammatory drug (NSAID), such as carprofen
Multimodal analgesia involves using different classes of drugs to block the pain pathway at multiple sites. Since the dog is already receiving a pure mu-opioid (fentanyl) that acts on central receptors, adding an NSAID (carprofen) is an excellent choice. NSAIDs work peripherally at the site of injury to reduce inflammation by inhibiting prostaglandin synthesis. Adding another opioid is redundant, an antagonist would reverse the analgesia, and while an NMDA antagonist is a valid part of a multimodal plan, an NSAID is a cornerstone for managing the inflammatory pain associated with orthopedic surgery.
DVM Doctor of Veterinary Medicine Anesthesia and Pain Management Questions and Answers
A 7-year-old cat with a known history of hypertrophic cardiomyopathy (HCM) requires anesthesia for a full-mouth dental extraction.
Which of the following induction agents should be used with the most caution due to its sympathomimetic effects, which increase heart rate and myocardial oxygen demand?