Anesthesia: free VTNE practice questions

Brachycephalic dogs have anatomic abnormalities (stenotic nares, elongated soft palate, everted laryngeal saccules, small-diameter trachea) that constitute brachycephalic obstructive airway syndrome (BOAS). They also have abnormally high parasympathetic tone, which can cause bradycardia during intubation and neck manipulation. The recommended protocol is to preoxygenate for 5 minutes before induction to maximize oxygen reserves, include an anticholinergic (atropine or glycopyrrolate) to stabilize heart rate, and perform rapid IV induction (with agents such as propofol, alfaxalone, or ketamine–midazolam) to gain immediate control of the airway. A laryngoscope is essential because redundant pharyngeal tissue obscures the laryngeal opening, and the required ETT is often smaller than expected for the dog's body weight.

Option A is wrong because the high parasympathetic tone makes bradycardia the risk, not tachycardia, so an anticholinergic is indicated.

Option C is dangerous: mask induction is associated with higher mortality in brachycephalic patients and delays airway control.

Option D reverses the tube-size guidance; a smaller tube is typically needed.

Inspired gas coming from a correctly functioning machine contains oxygen and inhalant anesthetic but no carbon dioxide, which is why a normal capnogram falls all the way to 0 mmHg during inspiration and stays there through the inspiratory baseline. A baseline that fails to return to 0 therefore has a specific meaning: carbon dioxide the patient already exhaled is being delivered back to it. On a rebreathing circuit there are two common causes. Either the absorbent in the canister is exhausted and can no longer strip carbon dioxide from the returning gas, or the expiratory unidirectional valve is not working and exhaled gas is travelling back down the inspiratory limb. Both raise the end-tidal value as well, because the patient starts each breath with carbon dioxide already in its airway.

Option B is the distractor most candidates take, and the difference is worth learning as a shape: hypoventilation makes the whole rectangle taller, raising the end-tidal number, but the baseline still returns to 0 because the machine is still removing carbon dioxide from the inspired gas. A raised baseline points at the equipment, not the patient's respiratory rate.

Option C describes a real problem with a different signature - a leaky cuff or partly kinked tube rounds off the edges of the waveform, producing a sloppy upstroke and downstroke rather than a lifted baseline, and the stem specifies that the corners are still square.

Option D is wrong because esophageal intubation causes a sudden loss of the waveform altogether, a flat line, since no carbon dioxide reaches the sensor at all.

Breathing circuit selection in small animal patients is made on body weight, and it is made before the patient is induced. Patients weighing less than 3 kg require a nonrebreathing circuit. At 2.5 kg this cat sits below that cutoff, and the rule is a requirement rather than a preference, which rules out options A and C.

Option D is the most tempting answer because it states a real rule for the wrong patient: the genuine choice between a rebreathing circuit fitted with pediatric breathing tubes and a nonrebreathing circuit belongs to patients weighing between 3 and 7 kg. Above that range, most small animal patients are anesthetized with inhalants delivered by an anesthesia machine outfitted with a rebreathing circuit, unless intramuscular or total intravenous techniques are used instead. The second lesson here is timing. During an induction, events follow one another in rapid succession - the anesthetic agents are given, the patient becomes unconscious and recumbent, the endotracheal tube is placed, secured, cuffed and attached to the machine, the vaporizer is turned on, the patient is positioned and monitoring begins - all within the first few minutes, and the technician does not have the luxury of leaving the patient to go and locate equipment. The circuit, the intubation supplies, the equipment for giving injections and administering fluids, and equipment to prevent hypothermia are all gathered, checked and organized beforehand, with a crash cart of emergency equipment and drugs always available.