General Anesthesia and Anesthetic Techniques
Conduct of the general anesthetic
Preoperative assessment sets risk: airway exam, ASA physical status, aspiration risk, and NPO intervals - 2 hours for clear liquids, 4 hours for breast milk, 6 hours for formula or a light meal, 8 hours for a fatty meal.
Induction choices follow hemodynamics: propofol causes vasodilation and apnea; etomidate is hemodynamically neutral but causes myoclonus and adrenal suppression; ketamine preserves pressure and bronchodilates. Neuromuscular blockers differ in onset, duration, and histamine release. Rapid sequence induction means preoxygenation, prompt induction, and prompt intubation; routine cricoid pressure is no longer standard.
Maintenance is inhalational (MAC-based) or total intravenous; monitoring includes capnography, agent analysis, and depth monitoring when indicated. At emergence, confirm train-of-four ratio above 0.9, adequate spontaneous ventilation, and protective reflexes.
Malignant hyperthermia: stop all triggers, hyperventilate with 100% oxygen, give dantrolene 2.5 mg/kg repeated as needed, cool actively, and treat hyperkalemia and acidosis.
Traps: processed EEG is an adjunct, not a substitute for clinical judgment; sevoflurane MAC-awake is roughly 0.34, so 0.5 MAC is not reliably a sleeping dose; PONV prophylaxis should be risk-stratified, not universal.
Worked example: the Apfel score adds one point each for female sex, nonsmoker status, prior PONV, and postoperative opioids. A score of 3 warrants two or three prophylactic agents from different classes.