Dynamic cerebral blood flow autoregulation during sevoflurane anesthesia and TIVA

Background : Dynamic cerebral blood flow autoregulation during sevoflurane anesthesia and total intravenous anesthesia (TIVA) is unclear. We examined the cerebral circulation autoregulation during anesthesia by sevoflurane or TIVA. Methods : We measured mean blood pressure (MBP) and blood flow velocity of the middle cerebral artery by a transcranial Doppler ultrasonography before and during anesthesia using sevoflurane [volatile induction and maintenance of anesthesia (VIMA) groups and using propofol and fentanyl (TIVA group), and the relationship between changes in MBP and cerebral blood flow velocity was evaluated using the method of transfer function analysis. We calculated transfer gain and coherence by cross-spectrum from autospectra of MBP and cerebral blood flow velocity. Results : Transfer gain during anesthesia by TIVA in the low frequency range and high frequency range was near 1 cm . sec -1 . mmHg -1 . It was about equal to the value of transfer gain before anesthesia. But transfer gain during anesthesia by VIMA was above 2 cm . sec -1 . mmHg -1 . Conclusion: These results suggest that TIVA by propofol and fentanyl maintains the dynamic autoregulation of cerebral blood flow, but sevoflurane impairs the autoregulation.