Anesthesia and Analgesia
Domain focus
Anesthesia and Analgesia tests preanesthetic assessment, drug selection, airway management, monitoring, and recovery. The exam expects you to match the circuit and oxygen flow to the patient and to recognize inadequate anesthesia or ventilation.
Core rules and concepts
- Assign an ASA physical status before anesthesia. American Society of Anesthesiologists classes range from I (healthy) to V (moribund), with E added for emergency.
- Premedication reduces stress and drug doses. Common classes include phenothiazines, alpha-2 agonists, benzodiazepines, and opioids; each has species-specific concerns.
- A rebreathing circuit is generally used for patients over about 7–10 kg, with oxygen flow of 20–50 mL/kg/min. Non-rebreathing circuits use about 200 mL/kg/min.
- Monitor depth, heart rate, rhythm, mucous membrane color, capillary refill, blood pressure, end-tidal CO2, and oxygen saturation. Capnography helps confirm intubation and ventilation.
- Recovery requires warmth, oxygenation, positioning, and frequent assessment until the patient can stand and swallow.
Worked example
An 8 kg dog is placed on a non-rebreathing circuit. Oxygen flow = 200 mL/kg/min × 8 kg = 1,600 mL/min = 1.6 L/min. The technician sets the flowmeter at 1.6 L/min and checks that the reservoir bag moves with each breath and that the patient is not breathing against a closed pop-off valve.
Traps that cost marks
Using a rebreathing circuit for a tiny patient; leaving the pop-off valve closed; failing to check cuff seal; and monitoring only heart rate while ignoring ventilation.