THE EFFECT OF NICARDIPINE ON CAROTID BLOOD-FLOW VELOCITY, LOCAL CEREBRAL BLOOD-FLOW, AND CARBON-DIOXIDE REACTIVITY DURING CEREBRAL ANEURYSM SURGERY

We studied the effects of nicardipine (initial infusion rate 0.5 mug.kg-1.min-1) on blood flow velocity in the internal carotid artery, local cerebral blood flow (LCBF), and carbon dioxide reactivity in 20 patients undergoing craniotomy for cerebral aneurysm clipping under isoflurane anesthesia. The blood flow velocity in the internal carotid artery was measured at T0 and T3 by a 20-MHz pulsed ultrasound Doppler flowmeter. LCBF was measured by the thermal gradient blood flow meter. Group A consisted of 10 patients with a good neurologic status (Hunt and Kosnik Grade 1); Group B consisted of 10 patients with a poor status (Grades II-IV). Nicardipine was infused until the mean arterial blood pressure decreased to about 75% of the initial value and was maintained at this level until the completion of aneurysm clipping. The measurements of hemodynamics and LCBF were performed after the exposure of the internal carotid artery (T0), and 10 and 30 min after the start of nicardipine (T1 and T2, respectively), before aneurysm clipping (T3), and 30 min after its discontinuation (T4). Carbon dioxide reactivity [% ALCBF/APaCO2 (%/mm Hg)] was evaluated at T0, T3, and T4. Mean arterial blood pressure decreased after nicardipine infusion in both groups. LCBF did not change during nicardipine infusion in either group. Blood flow velocity increased significantly in Group A after nicardipine infusion from 45.1 +/- 6.9 to 51.5 +/- 6.4 cm/s (P < 0.05), but in Group B flow velocity did not change. Carbon dioxide reactivity did not change after nicardipine infusion but correlated with LCBF before (r2 = 0.495, P < 0.05), during (r2 = 0.706, P < 0.01), and after hypotension (r2 = 0.555, P < 0.05). These results suggest that nicardipine may be a useful drug to treat intraoperative hypertension during cerebral aneurysm surgery.