Hypotensive actions of diltiazem and nitroprusside compared during fentanyl anaesthesia for total hip arthroplasty

The potential for inducing hypotension during fentanyl anaesthesia by administering either diltiazem (n = 7) or sodium nitroprusside (n = 7) was investigated during total hip arthroplasty. Haemodynamic variables were obtained in the lateral position before, during and after administration of the hypotensive agent. Diltiazem 0.15 mg X kg-1 given as an IV bolus followed by a 12.5 +/- 3 micrograms X kg-1 X min-1 continuous infusion decreased mean arterial pressure (MAP) from 77 +/- 11 mmHg to 63 +/- 16 mmHg (p less than 0.05) while other haemodynamic parameters showed only minor and insignificant changes. Hypotension continued for at least 30 min after the cessation of diltiazem. With sodium nitroprusside MAP decreased immediately from 81 +/- 11 mmHg to 59 +/- 9 mmHg (p less than 0.01) and rapidly returned to its control value after cessation of the infusion. CI and Qs/Qt rose significantly (p less than 0.05) while the systemic vascular resistance index (SVRI) (p less than 0.01) and pulmonary vascular resistance index (PVRI) (p less than 0.05) fell significantly. The haemodynamic profile was significantly different between hypotensive agents for MAP (p less than 0.02), heart rate (HR) (p less than 0.01), SVRI (p less than 0.05), and PVRI (p less than 0.05). HR was lower with diltiazem than with nitroprusside. A bradycardia less than 50 beats/min was observed in five patients in the diltiazem group. MAP, SVRI and PVRI were lower with nitroprusside than with diltiazem. Diltiazem can induce and maintain moderate hypotension without tachycardia and decreased cardiac output in humans during fentanyl anaesthesia but the modulation of the level of arterial pressure and the depression of atrioventricular conduction are unpredictable.