Comparison of intravenous nitroprusside, nitroprusside-captopril, and nitroglycerin for deliberate hypotension during posterior spine fusion in adults.

Three techniques for deliberate hypotension (mean arterial pressure, 60 to 70 mmHg) were prospectively compared in adults undergoing posterior spine fusion. Patients received either IV sodium nitroprusside, sodium nitroprusside with oral captopril pretreatment, or IV nitroglycerin. Patient groups were comparable in age, sex, weight, baseline hemodynamic and laboratory parameters, duration of surgery, and duration of hypotension. Absolute blood loss was significantly less in the group receiving nitroglycerin; however, there were no differences between groups when corrected for operative exposure (milliliter per spine segment exposed). Nitroprusside was effective in producing target blood pressure in all patients. Nitroglycerin was ineffective in two patients and two other patients required greater than 20 micrograms/kg/min. Both groups receiving nitroprusside developed significant postinfusion increases in arterial pressure. Blood pressure fell significantly after induction of anesthesia in patients receiving captopril. Cardiac index, heart rate, pulmonary capillary wedge pressure, intrapulmonary shunt, and arterial blood gases were comparable and did not change significantly in any group. Systemic vascular resistance fell during infusion in all groups and remained depressed after infusion in patients receiving nitroglycerin. Plasma renin activity was significantly increased in the group receiving captopril due to loss of feedback inhibition of renin release and rose significantly during infusion in those patients receiving nitroprusside alone. There were no complications. Nitroprusside with and without captopril pretreatment was associated with postoperative increases in arterial pressure, although not to hypertensive levels, probably due to loss of captopril activity after single-dose administration. The use of nitroglycerin was limited by lack of potency. There was no demonstrable clinical advantage for any of the three techniques.