Diazepam-fentanyl interaction--hemodynamic and hormonal effects in coronary artery surgery.

Diazepam has been reported to produce hypotension when administered with anesthetic doses of fentanyl. Twenty patients undergoing coronary bypass surgery were randomly assigned to one of four treatment groups: group 1, no diazepam; groups 2, 3, and 4, 0.125, 0.25, and 0.5 mg X kg -1 of diazepam, respectively. All patients then received 50 micrograms X kg -1 fentanyl at 400 micrograms X min -1 and 0.4 mg X kg -1 metocurine at 2 mg X min -1. Hemodynamic parameters were recorded and blood was sampled for measurement of plasma catecholamine and histamine concentrations. Heart rate, cardiac index, stroke volume index, central venous pressure, pulmonary arterial and wedge pressures, and pulmonary vascular resistance did not change significantly in any group. Patients in groups 2-4 had significant decreases in mean arterial pressure and systemic vascular resistance during fentanyl infusion. These hemodynamic changes were accompanied by decreases in plasma epinephrine and norepinephrine levels. These hemodynamic and hormonal changes did not occur in patients given fentanyl only. Plasma histamine levels did not change significantly in any group. Caution should be used when diazepam in doses as small as 0.125 mg X kg -1 are combined with high-dose fentanyl anesthesia.