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 cardiopulmonary bypass (CPB) with stable hypothermia (32 degrees C) in fentanyl-anesthetized patients. Middle cerebral artery transcranial Doppler flow 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 range of 40-80 mm Hg by sodium nitroprusside and phenylephrine before (control) and during propofol infusion, with a stable plasma concentration (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 control. The slopes of the curves relating CBFV and COE to cerebral perfusion 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 CPB. 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 induced 35% and 10% decreases in CBFV and cerebral oxygen extraction, respectively. The slope of the curve relating cerebral perfusion pressure to CBFV decreased with propofol.