THE EFFECTS OF PROPOFOL ON CEREBRAL BLOOD-FLOW VELOCITY AND CEREBRAL OXYGEN EXTRACTION DURING CARDIOPULMONARY BYPASS

We investigated the effects of burst-suppression doses of propofol on cerebral blood flow velocity (CBFV), cerebral oxygen extraction (COE), and dynamic autoregulation in 20 patients undergoing cardiac surgery. The experimental procedure was performed during nonpulsatile cardiopu lmonary bypass (CPB) with stable hypothermia (32 degrees C) in fentany l-anesthetized patients. Middle cerebral artery transcranial Doppler f low velocity, right jugular bulb oxygen saturation, and jugular venous pressure (JVP) were continuously measured. Dynamic autoregulation was tested by stepwise changes in mean arterial pressure (MAP) within a r ange of 40-80 mm Hg by sodium nitroprusside and phenylephrine before ( control) and during propofol infusion, with a stable plasma concentrat ion (approximately 9 mu g/mL). Propofol induced a 35% decrease in CBFV (P < 0.0001) and a 10% decrease in COE (P < 0.05) compared with contr ol. The slopes of the curves relating CBFV and COE to cerebral perfusi on pressure (CPP = MAP - JVP) were less pronounced with propofol (P < 0.01 and P < 0.05, respectively). We conclude that propofol decreases CBFV and improves dynamic autoregulation during moderate hypothermic C PB. Furthermore, during propofol infusion, cerebral blood flow was in excess relative to oxygen demand, as indicated by the decrease in COE. Implications: In this study, we evaluated the effects of propofol on continuously measured cerebral blood flow velocity (CBFV) and cerebral oxygen extraction as a function of perfusion pressure. Propofol induc ed 35% and 10% decreases in CBFV and cerebral oxygen extraction, respe ctively. The slope of the curve relating cerebral perfusion pressure t o CBFV decreased with propofol.