Effect of ketanserin on phenylephrine-dependent changes in splanchnic hemodynamics and systemic blood pressure in healthy subjects.

We studied the effect of ketanserin on basal status and phenylephrine-dependent changes in arterial blood pressure and splanchnic hemodynamics in seven healthy subjects. The drug was administered as an intravenous bolus of 10 mg followed by infusion of 4 mg/h. After a basal period of saline or ketanserin infusion, phenylephrine was infused at a constant rate in a fixed dose sequence of 1, 2, and 3 micrograms/kg/min. Blood pressure was measured intraarterially. Splanchnic blood flow, mean wedged hepatic blood pressure, and splanchnic vascular resistance were assessed by means of the hepatic venous catheter technique using indocyanine green dye. At steady-state plasma concentrations, basal arterial pressure and heart rate were not altered in this small group of normal subjects, whereas mean wedged hepatic venous pressure was lowered by ketanserin. During saline infusion, phenylephrine provoked a dose-dependent rise in arterial and wedged hepatic blood pressure; these effects were attenuated by ketanserin. Phenylephrine induced a significant, but not dose-dependent, decrease in estimated splanchnic blood flow. Ketanserin did not relevantly influence basal or phenylephrine-dependent splanchnic blood flow. We suggest that the hypotensive action of ketanserin is in part related to an interaction at alpha 1-adrenoceptors. Moreover, a dissociation of effects on vascular alpha-receptors seems to exist in the splanchnic and systemic circulations.