Basic Sciences: Physics, Physiology, Pharmacology, and Anatomy
Core science that changes clinical decisions
Physics: understand partial pressure versus concentration, solubility, diffusion, and flow. Henry's law explains why volatile uptake depends on blood solubility; Poiseuille's law explains resistance changes with tube radius; Bernoulli and Venturi principles underlie jet ventilation and nebulizers. Physiology: oxygen delivery (DO2 = CO × CaO2), alveolar gas equation, West zones, compliance, dead space, renal handling, and cerebral autoregulation. Pharmacology: pharmacokinetics (distribution, clearance, context-sensitive half-time), pharmacodynamics (receptors, dose-response), and MAC. Anatomy: airway landmarks, neuraxial spaces, brachial plexus, and danger zones for blocks.
Traps: MAC is not a measure of potency in the usual higher-is-stronger sense-it is the inverse. MAC values are additive and altered by age, temperature, pregnancy, and drugs. A normal pulse oximeter does not exclude hypercapnia or anemia. Solubility differences explain why desflurane washes in and out faster than isoflurane. Do not confuse partial pressure with volume percent when interpreting gas tensions.
Worked example: a 70-kg patient receives lidocaine 1.5 mg/kg for a block. Dose = 105 mg. If using 1% lidocaine (10 mg/mL), volume = 10.5 mL. Always calculate cumulative dose across multiple blocks and add epinephrine only when indicated; the maximum is a guide, not a guarantee against toxicity.
Rule of thumb: when a physiologic or pharmacologic number seems surprising, trace it back to partial pressure, flow, solubility, or clearance rather than memorizing an isolated value.