Pharmacology  ·  General Anesthesia

Inhalational Anesthetic Agents

Comparative pharmacokinetics, distinguishing properties, and clinical selection

• Two molecular mechanisms are at work here, not one. The halogenated volatile agents potentiate the gamma-aminobutyric acid type A receptor; nitrous oxide instead antagonizes the N-methyl-D-aspartate receptor. That single divergence explains why nitrous oxide is analgesic, why it sits apart in every panel below, and why it alone does not trigger malignant hyperthermia.
• The comparative table is ranked by blood:gas partition coefficient, so the first two columns move together and predict induction and emergence speed. Potency, in the third column, tracks lipid solubility instead and runs in the opposite direction — the slowest agent is also the most potent.
• The rightmost column is where agent selection actually happens. Speed and potency rarely decide a case; the distinguishing feature or the disqualifying hazard usually does.
• Three agents get their own hazard cards because their serious adverse effects are agent-specific rather than shared across the class. Halothane and enflurane remain here despite being largely withdrawn in high-resource settings — halothane is still in wide use where cost governs, and both anchor the contrasts that make the modern agents intelligible.
• The closing box inverts the logic of everything above it, working from the patient's situation back to the agent. Read it as the practical output of the two panels that precede it.