Hemodynamic effects of N2O, O2 barbiturate anesthesia and induced hypotension in early versus late aneurysm clipping.

The cardiovascular effects of large dose thiopental anesthesia and induced hypotension were examined in 22 patients undergoing clipping of ruptured intracranial aneurysms. Eleven patients operated on within 4 days of the initial bleed (early group) were compared with those operated on more than 10 days after the bleed (late group). Systemic and pulmonary arterial pressures, central venous pressure, and cardiac output were measured. The cardiac index and the systemic and pulmonary vascular resistance were calculated. Before the induction of anesthesia, the cardiac index was 4.00 +/- 0.3 litres/minute/m2 in the early group compared with 2.89 +/- 0.23 litres/minute/m2 in the late group (P less than 0.05). Five and 10 minutes after the administration of mannitol (1 g/kg) and at an induced hypotensive level of 60 torr, the cardiac index remained significantly higher in the early group (P less than 0.05). There was no significant difference in the mean arterial blood pressure between the groups. Systemic vascular resistance was significantly higher in the late group during the postinduction and the pre-mannitol infusion periods and at induced hypotensive levels of 50 and 40 torr. Central venous pressure was significantly higher in the early group only at the preanesthesia (control) measurement. There was no significant difference between the groups in the pulmonary artery wedge pressure or the pulmonary vascular resistance.