Adrenergic response to nicardipine in the management of postoperative hypertension.

Nicardipine, a new dihydropyridine calcium channel blocking agent, has been shown to be effective in the management of hypertension. The adrenergic response to intravenous nicardipine as measured by changes in plasma catecholamine concentrations in seven patients undergoing treatment of postoperative hypertension is reported. Postoperative hypertension was defined as a systolic blood pressure (SBP) greater than 140 mm Hg. Nicardipine or placebo was administered in doses of 10 mg/h, 12.5 mg/h, and 15.0 mg/h for 5 minutes, 5 minutes, and 15 minutes, respectively, to achieve a therapeutic response defined as a reduction of SBP of 15% or more. Once a therapeutic response occurred, patients entered a maintenance period when the study drug infusion rate was reduced to the equivalent of 3.0 mg/h, and the dose was adjusted by 1.0 to 2.5 mg/h every 15 minutes as needed to maintain blood pressure control. Patients who did not respond to the study drug had their treatment code broken and, if on placebo, received open-label nicardipine. Blood samples were taken for the measurement of plasma norepinephrine (NE) concentrations at baseline prior to nicardipine infusion, at the time of therapeutic response, during maintenance, and after discontinuation of nicardipine. There were no significant differences between the baseline heart rate prior to nicardipine infusion and at the time of therapeutic response, during maintenance, or after discontinuation of the infusion. Mean NE concentrations at baseline prior to nicardipine infusion were 589.3 +/- 140.1 pg/mL (normal range, 75 to 480 pg/mL). Thus, hypertensive patients in the recovery room have a high degree of background sympathetic stimulation. Nicardipine did not further increase plasma NE levels.(ABSTRACT TRUNCATED AT 250 WORDS)