Sympathoneuronal and sympathoadrenal activation during ketamine anesthesia.

The effects of ketamine anesthesia (3 mg/kg i.v.) on cardiovascular parameters and noradrenaline, adrenaline and dopamine-beta-hydroxylase (DBH) activity in plasma were studied in 12 patients. At 3, 6 and 10 min after induction of anesthesia, a pronounced increase in heart rate (+28%) and in systolic and diastolic blood pressure (+28% and 17% resp.) was observed. Concomitantly noradrenaline and adrenaline concentrations increased significantly from 187 to 415 ng/l and from 97 to 271 ng/l, respectively. DBH-activity in plasma remained almost unchanged. From these results it can be concluded that the well known cardiovascular stimulant effect of ketamine is due to greatly enhanced sympatho-neuronal and sympatho-adrenal activity, presumably brought about by a central mechanism of action of the drug. Furthermore, DBH-activity in plasma appeared not to be a reliable index of sympathetic activity in man.