General Anesthetics: HALOTHANE

: The first of the more modern agents, it is a halogenated hydrocarbon. (Halogens are Cl, F, Br, I)—all the GA’s from now on will be halogenated. Has 3 F- attached, was synthesized by the Brits in the 1950s. Halothane is still widely used and is a standard for halogen compounds.

-Very potent (MAC=0.75)

-very fat soluble

-strong myocardial depressant, negative inotropic effect; relaxes sm. Muscle, decreased TPR

-depresses sympathetic NS, no catecholamine release

-HALLMARK: causes hypotension

-does NOT follow guedel signs

-must monitor bp for depth of anesthesia

-baroreceptor reflex depression

-overall hypotension, bradycardia, decreased C.O.

-NOT compatible with epinephrine, danger of arrhythmia, sensitizes to catecholamines

-poor analgesic, often used with nitrous oxide

-inadequate muscle relaxant so usually given with a muscle relaxant

-15% metabolized in liver, concern of liver toxicity (“halothane hepatitis”)… this is rare, and often occurs only after repeated exposures to halothane. In any case halothane is contraindicated in pts with liver problems.

-moderately fast acting, Oswald coefficient= 2.3

-cardiovascular depressant, respiratory depressant, can produce malignant hyperthermia (MH)

Category: Pharmacology Notes