Dynamic cerebral autoregulation during sevoflurane anesthesia: a comparison with isoflurane.

UNLABELLED: We investigated dynamic cerebral pressure autoregulation awake and during 1.5 minimum alveolar anesthetic concentration (MAC) sevoflurane or isoflurane anesthesia in 16 patients undergoing nonintracranial neurosurgical procedures. All patients received a standardized anesthetic, and their lungs were ventilated with 1.5 MAC volatile anesthetic in 100% oxygen to normocapnia. Routine monitors included electrocardiogram, pulse oximetry, end-tidal capnography, and continuous noninvasive blood pressure. In addition, middle cerebral artery blood velocity (Vmca) was measured continuously using transcranial Doppler ultrasonography. Dynamic cerebral autoregulation was tested by inducing a rapid transient decrease in mean arterial pressure by deflation of large thigh cuffs, which were placed around both thighs and inflated to 100 mm Hg above systolic pressure. The Vmca response to the decrease in blood pressure was fitted to a series of curves to determine the rate of dynamic cerebral autoregulation (dRoR). Awake dRoR values were similar in the isoflurane and sevoflurane groups, 32 +/- 2%/s and 29 +/- 2%/s, respectively. dRoR decreased to 5 +/- 1%/s during isoflurane anesthesia but to only 24 +/- 2%/s during sevoflurane anesthesia. We conclude that dynamic cerebral autoregulation is better preserved during sevoflurane than isoflurane anesthesia in humans. IMPLICATIONS: We investigated the effect of sevoflurane and isoflurane on dynamic cerebral pressure autoregulation using transcranial Doppler ultrasonography. At 1.5 minimum alveolar anesthetic concentration, dynamic autoregulation was better preserved during sevoflurane than isoflurane anesthesia.