RESUMO
OBJECTIVE: Pharmacologically induced electroencephalogram (EEG) silence increases tolerance of ischemic period by reducing cerebral metabolism. We hypothesized that sevoflurane, a cerebral vasodilator, will maintain cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) better than propofol, a cerebral vasoconstrictor, during EEG silence. To validate this, we compared the effect of sevoflurane and propofol on CBF and CMRO2 during surgical plane of anasthesia (SP) and burst suppression on EEG (BS). METHODS: We conducted a prospective, double-blinded trial where patients undergoing neurosurgery were randomized to receive propofol or sevoflurane. Mean velocity (MV) and pulsatility index (PI) of bilateral middle cerebral arteries (MCA) were measured as surrogate of CBF. Jugular venous oxygen saturation (SjvO2) and arteriovenous oxygen difference (AjvDO2) were obtained to assess CMRO2. The values were compared between groups using Student t test and within the group with analysis of variance at SP and BS. RESULTS: BS decreased MV and increased PI in propofol group (P < 0.001 and P < 0.02 on normal side, P < 0.004 and P < 0.001 on tumor side). There was no significant change in sevoflurane group. BS with sevoflurane increased SjvO2 (P < 0.001) and decreased AjvDO2 (P < 0.001). Change in SjvO2 and AjvDO2 with propofol at SP and BS was variable. CONCLUSIONS: In our study, sevoflurane had a safer profile on cerebral oxygenation during BS while not altering the CBF, suggesting increased availability of oxygen. Propofol, on the other hand, produced cerebral vasoconstriction with BS. The effect of propofol on oxygenation was unpredictable, with low SjvO2 and high AjvDO2 even at surgical plane of anesthesia.
