Plasma concentration and E.E.G. after various regimens of etomidate

Etomidate was injected i.v. within 10 or 60 s at various doses. After etomidate 0.3 mg kg-1 the plasma concentration was 1.6 micrograms ml-1 at 1 min after the end of injection. For about 7 min a good hypnotic effect (stages C0-D2) was observed on the e.e.g. recording. For surgical procedures, however, a combination with analgesic drugs appeared to be necessary. When the dose of etomidate was increased (0.1-0.4 mg kg-1) a linear increase in plasma concentration and slow e.e.g. activity was observed concomitantly. Anaesthesia could be prolonged with additional injections or with continuous infusion. Each additional injection produced a steep increase in concentration of short duration with marked deepening of hypnosis. The infusion induced only a moderate increase in plasma concentration, whereas the depth of sleep during the period of infusion remained nearly the same. E.e.g. changes induced by etomidate are similar to those after barbiturates and other i.v. anaesthetics.