Effects of droperidol on sympathetic activity and baroreflex control of heart rate in humans.

The effects of intravenous droperidol, 0.2 mg . kg-1, on baroreflex control of heart rate and on plasma catecholamine levels were determined in 10 ASA physical status I unpremedicated patients. Baroreflex control of heart rate was assessed by a pressor test using phenylephrine. Plasma concentrations of norepinephrine and epinephrine were determined by high pressure liquid chromatography, and plasma droperidol concentrations were measured by radioimmunoassay, from blood samples withdrawn before baroreflex evaluation. All data were obtained before and 5, 10, and 15 min following droperidol administration. Baroreflex response was significantly decreased after droperidol at each time of the study with the maximal decrease (-47% from control) observed at 5 min. No resetting of baroreflex was present since the pulse interval at the reference pressure was unchanged. Plasma norepinephrine concentrations were moderately but significantly increased only at 5 min, while no significant change in epinephrine concentrations was observed. It is concluded that droperidol induces a moderate but sustained alteration of baroreflex function and a transient increase in plasma norepinephrine concentrations.