In this study, we investigated the effect of sevoflurane on cerebral blood flow (CBF) autoregulation in rats. Twenty-four male Sprague-Dawley rats were randomly assigned to receive one of the following anesthetic treatments. In Group 1 (n = 8, control) anesthesia was maintained using fentanyl (25 microg x kg(-1) x h(-1)) and N2O/O2 (fraction of inspired oxygen 0.33). In Group 2 (n = 8) and Group 3 (n = 8), anesthesia was maintained using 2% sevoflurane (1 minimum alveolar anesthetic concentration [MAC]) and 2 MAC sevoflurane (4 vol%) in O2/air (fraction of inspired oxygen 0.33), respectively. Cortical CBF autoregulation was measured during graded hemorrhage within the mean arterial pressure (MAP) range of 100-30 mm Hg using laser Doppler flowmetry. CBF was constant with fentanyl/ N2O (Group 1) and 1 MAC sevoflurane (Group 2) within the MAP range of 100-40 mm Hg. In Group 3 (2 MAC sevoflurane), CBF decreased as a linear function of hemorrhagic hypotension. These results indicate that CBF autoregulation was intact during 1 MAC sevoflurane. In contrast, CBF autoregulation was impaired with 2 MAC sevoflurane. This is probably related to a reduction of baseline cerebrovascular tone with higher concentrations of sevoflurane, which results in a decreased capacity of autoregulatory cerebrovascular dilation during hemorrhage.
Implications: The purpose of the present study was to investigate the effect of sevoflurane on cerebral blood flow autoregulation in rats. Cerebral blood flow autoregulation was intact with 1 minimum alveolar anesthetic concentration sevoflurane but was impaired with 2 minimum alveolar anesthetic concentration sevoflurane.