Anesthesia and Analgesia
The anesthetic plan
Understand the pieces: premedication (opioid, alpha-2 agonist, benzodiazepine, anticholinergic), induction (propofol, alfaxalone, ketamine combinations), and maintenance (inhalant such as isoflurane or sevoflurane, or an injectable constant-rate infusion). Match the protocol to the patient's ASA status, age, and disease. Premedication reduces induction drug requirements and provides pre-emptive analgesia.
Equipment and breathing systems
Rebreathing circuits suit larger patients; non-rebreathing circuits suit small patients (roughly under 5–7 kg). Oxygen flow is about 200–300 mL/kg/min in a non-rebreathing system versus 20–40 mL/kg/min in a rebreathing system. Select an endotracheal tube that allows a seal with minimal cuff inflation, and verify placement by chest auscultation and capnography.
Monitoring depth and safety
Assess depth by jaw tone, palpebral reflex, eye position, heart rate, and respiratory pattern. Monitor oxygenation (SpO2), ventilation (ETCO2 about 35–45 mmHg), blood pressure (aim for mean arterial pressure at least 60 mmHg), temperature, and mucous membrane color. Prevent and treat hypothermia, hypotension, bradycardia, and apnea promptly; keep fasting times modest, especially in pediatric or debilitated patients.
Recovery
Provide warmth, oxygen, analgesia, and continuous observation until the patient is sternal and swallowing.
Worked example
A 4 kg cat on a non-rebreathing circuit: 200 mL/kg/min × 4 kg = 800 mL/min of oxygen.
Traps
Deepening anesthesia to fix hypotension, forgetting that bradycardia with pale membranes signals a problem, and leaving a patient unmonitored during recovery.