THE EFFECT OF REMIFENTANIL ON CEREBRAL BLOOD-FLOW VELOCITY

In the present study, we investigated the effect of remifentanil on ce rebral blood flow velocity (CBFV). We investigated 20 patients (ASA ph ysical status III) scheduled for elective coronary artery bypass graft surgery. Anesthesia was induced with remifentanil 5 mu g/kg nr (Group 1, n = 10) or 2 mu g/kg TV (Group 2, n = 10) and was maintained with 3 mu g kg-l min-l IV (Group I)or 1 mu g kg(-1) min(-1) IV (Group 2). P ancuronium (0.1 mg/kg TV) was administered for muscle relaxation. Assi sted ventilation followed by controlled ventilation via a mask was per formed with the Pace, kept constant. Mean cerebral blood flow velocity (Vmean) was measured in the middle cerebral artery using a transcrani al Doppler sonography system. Mean arterial pressure (MAP) was kept co nstant by the IV administration of norepinephrine. Measurements were m ade at baseline and every minute after remifentanil infusion for 10 mi n. Data were analyzed by using analysis of variance and a post hoc t-t est (P < 0.05). Heart rate, MAP, and Pace, did not change over time in either group. Vmean did not change in Group 2. In contrast, there was a 31% decrease of Vmean in Group 1 (P < 0.05). The results show that large-dose, but not moderate-dose, remifentanil reduces CBFV unrelated to any changes in systemic hemodynamics in isocapnic cardiac patients . Implications: Transcranial Doppler sonography was used to monitor re mifentanil-induced changes in cerebral perfusion. We found that large doses of remifentanil reduced cerebral blood flow velocity despite con stant perfusion pressure. This may implicate a central mechanism for c erebral hemodynamic effects of remifentanil.