EFFECTS OF PROPOFOL ON CEREBRAL BLOOD-FLOW, METABOLISM, AND CEREBRAL AUTOREGULATION IN THE ANESTHETIZED PIG

We studied the effects of propofol on the cerebral circulation and flo w/pressure autoregulation in eight anesthetized pigs. Regional cerebra l blood flow (rCBF) was measured with a cerebral venous outflow techni que. Autoregulation was tested with angiotensin infusions and gradual blocks of the caval vein for hyper- and hypotensive challenges, respec tively. Propofol was given in a bolus of 2.5 mg . kg(-1) followed by a n infusion starling at 12 mg . kg(-1). h(-1) and gradually reduced to 8 mg . kg(-1). h(-1). As expected, propofol caused a substantial reduc tion in cerebral metabolic rate of oxygen, which was accompanied by an increase in cerebrovascular resistance and a decrease in CBF. In the control situation, i.e., during background anesthesia (low-dose isoflu rane + nitrous oxide) only, the autoregulation was well preserved, and its lower Limit was found at a mean arterial blood pressure (MABP) of 48 mm Hg, Propofol did not affect autoregulation in the group as a wh ole: the slope of the regression line of regional cerebrovascular resi stance (rCVR) versus MABP during blood pressure reduction (caval test) was not significantly changed during propofol when compared to the co ntrol, neither was the lower limit of autoregulation (MABP, 54 mm Hg). All pigs but one followed this response pattern. The nonautoregulatin g pig had a completely pressure-dependent rCBF during propofol anesthe sia, despite a perfectly intact autoregulation in the control situatio n. It is concluded that propofol in clinical dosage does not affect au toregulation in this pig model, although individual animals may displa y a different response pattern.