Special Populations and Subspecialty Anesthesia
Special populations change the dose and the danger
Pediatrics: larger head, small airway, high oxygen consumption, immature renal and hepatic clearance, and temperature vulnerability. Use weight-based dosing, uncuffed or cuffed tube sizing, and careful fluid boluses. Obstetrics: increased plasma volume, aortocaval compression, aspiration risk, and altered MAC; use left uterine displacement, rapid sequence induction when indicated, and prepare for hemorrhage and preeclampsia. Geriatrics: reduced MAC, polypharmacy, frailty, and delirium risk. Obesity: dose lipophilic drugs on total body weight cautiously, use ideal body weight for ventilation, and position carefully. Also know cardiac, neuro, trauma, and ambulatory considerations.
Traps: pediatric doses are not simply scaled adult doses. Pregnant patients desaturate quickly because functional residual capacity falls. Succinylcholine is relatively contraindicated in hyperkalemia risk. In obesity, do not use total body weight for all drug doses.
Worked example: a 5-year-old needs a cuffed tracheal tube. Formula: internal diameter (mm) = age/4 + 3.5 = 1.25 + 3.5 = 4.75, so choose 4.5–5.0 mm and confirm leak.
Rule of thumb: in special populations, start lower, titrate slower, and monitor longer.