Specialty and Subspecialty Anesthesia
Pediatrics
Neonates have MAC roughly 30% below older infants, immature hepatic and renal clearance, higher total body water, and bradycardia as the dominant response to hypoxia. The infant larynx is rostral and cephalad. Key reading points: weight-based dosing, maintenance fluids by the 4-2-1 rule, and pyloric stenosis with hypochloremic, hypokalemic metabolic alkalosis that must be corrected before anesthesia.
Obstetrics
Aortocaval compression begins near 20 weeks (left uterine displacement), anesthetic requirements fall, functional residual capacity is low with high oxygen consumption so desaturation is rapid, and aspiration risk is elevated. Magnesium potentiates nondepolarizing blockers. Preeclampsia warrants platelet assessment before neuraxial technique.
Cardiac and thoracic
With low ejection fraction, preserve systemic vascular resistance and avoid negative inotropy. Protamine reversal after bypass can cause histamine-mediated hypotension, pulmonary vasoconstriction, and anaphylactoid reactions. One-lung ventilation hypoxemia is treated with CPAP to the operative lung, PEEP to the dependent lung, recruitment, and intermittent two-lung ventilation.
Neuroanesthesia
CPP = MAP - ICP. Mannitol 0.5-1 g/kg for intracranial pressure; hyperventilation is a short-term bridge only. Total intravenous anesthesia is preferred when evoked potentials are monitored.
Ambulatory and geriatric
Risk-stratify postoperative nausea and vomiting (Apfel score) and use at least two prophylactic agents in high-risk patients. Older adults have reduced MAC, less physiologic reserve, and greater sensitivity to sedatives.
Traps
Reading reduced MAC as requiring more agent; assuming a single pediatric mg/kg dose scales perfectly across ages; forgetting that a scalp block does not treat elevated ICP from hypoventilation.
Worked example
22-kg child: maintenance = 4 x 10 + 2 x 10 + 1 x 2 = 62 mL/h.