Anesthesia and Analgesia
Anesthesia and analgesia tests premedication, induction, maintenance, monitoring, recovery, and multimodal pain management. The exam focuses on drug classes, equipment checks, physiologic monitoring, and recognizing complications before they become emergencies.
Core rules and concepts
- ASA physical status ranges from I (healthy) to V (moribund), with E added for emergency. Higher status demands more conservative drug choices and closer monitoring.
- Know drug classes: alpha-2 agonists provide sedation and analgesia but cause bradycardia and vasoconstriction; benzodiazepines provide muscle relaxation and anticonvulsant effects; dissociatives such as ketamine provide analgesia and preserve airway reflexes; propofol allows rapid induction and intubation.
- Inhalant MAC describes potency: lower MAC means a more potent agent. Monitor depth with jaw tone, eye position, palpebral reflex, and response to stimulation.
- Capnography confirms tube placement and ventilation; a normal end-tidal CO2 is roughly 35–45 mmHg. Pulse oximetry estimates oxygen saturation but is affected by poor perfusion and motion.
- Multimodal analgesia combines opioids, NSAIDs when safe, local blocks, and other modalities. NSAIDs are avoided in hypotension, dehydration, or renal compromise.
Worked example
A 10 kg dog is premedicated with dexmedetomidine at 5 mcg/kg. The concentration is 0.5 mg/mL, which equals 500 mcg/mL. Dose = 10 × 5 = 50 mcg. Volume = 50 ÷ 500 = 0.1 mL. Draw the volume with a 1 mL syringe, double-check the concentration, and record the drug, dose, route, and time.
Traps that cost marks
- Skipping the anesthesia machine leak check and oxygen flush test.
- Ignoring a rising end-tidal CO2 or a capnogram waveform that suggests obstruction.
- Allowing hypothermia during long procedures; actively warm the patient.
- Giving an NSAID to a hypotensive or dehydrated patient.