Anesthesia and Analgesia
Anesthesia and analgesia questions test premedication choices, breathing-circuit selection, monitoring, and recovery. You must connect patient size and condition to equipment and drug effects.
Core rules
- Classify the patient (ASA) and choose premedication for sedation, analgesia, and cardiovascular stability. Opioids provide analgesia; alpha-2 agonists provide sedation and analgesia but cause bradycardia and vasoconstriction.
- Non-rebreathing circuits suit small patients (generally under 5–7 kg) because they have low resistance; rebreathing circuits conserve gas and heat in larger patients.
- Calculate oxygen flow for a non-rebreathing circuit at 100–300 mL/kg/min; for a rebreathing circuit use 10–20 mL/kg/min plus circuit requirements.
- Monitor HR, RR, mucous membrane color, CRT, blood pressure, SpO2, ETCO2, and temperature. Capnography confirms tube placement and ventilation.
- Check the endotracheal tube cuff: inflate until no leak at peak inspiration, not to a fixed volume.
Worked example
A 3 kg cat is on a non-rebreathing circuit at 200 mL/kg/min. 3 × 200 = 600 mL/min, or 0.6 L/min. If the flowmeter is marked in L/min, set 0.6, not 6. Reasoning: mL/min divided by 1,000 gives L/min.
Traps
- Assuming a pulse oximeter is reliable in a cold, vasoconstricted patient.
- Overinflating the cuff and damaging the trachea.
- Forgetting active warming; small patients lose heat rapidly.
- Using a rebreathing circuit for a 2 kg patient without adjusting for valve resistance.