The Effect of Thiopental Metabolism on Duration of Anesthesia

Abstract

A difference between arterial and hepatic venous thiopental concentrations of 6.6 and 15.1% was found in dogs after 3 and 5 hours, respectively, following intravenous injection of 30 mg thiopental/pound. This and similar data in man were used to predict, in an electrical analog, the effect of liver thiopental metabolism on the rate of fall of arterial thiopental concentration. Contrary to previous belief the authors found that metabolism is of major importance in the early rapid reduction of arterial levels and hence plays an major role in the early awakening seen with this anesthetic. Although uptake in muscle still plays the dominant role in the early fall of the arterial concentration, this was equalled by the additive effect of metabolism and uptake in fat.