Cerebral haemodynamic changes during propofol-remifentanil or sevoflurane anaesthesia: transcranial Doppler study under bispectral index monitoring

Background. Sevoflurane or propofol–remifentanil-basedanaesthetic regimens represent modern techniques for neurosurgicalanaesthesia. Nevertheless, there are potential differences relatedto their activity on the cerebrovascular system. The magnitudeof such difference is not completely known. Methods. In total 40 patients, treated for spinal or maxillo-facialdisorders, were randomly allocated to either i.v. propofol–remifentanilor inhalational sevoflurane anaesthesia. Transcranial Dopplerwas used to assess changes in cerebral blood flow velocity,carbon dioxide reactivity, cerebral autoregulation and the bispectralindex to assess the depth of anaesthesia. Results. Time-averaged mean flow velocity (MFV) was significantlyreduced after induction of anaesthesia in both sevoflurane andpropofol–remifentanil groups (P<0.001). At deeper levelsof anaesthesia, MFV increased in the sevoflurane group, suggestingan uncoupling flow/metabolism, whereas it was further reducedin the propofol–remifentanil group (P<0.001). Indicesof cerebral autoregulation were reduced in patients with high-dosesevoflurane whereas autoregulation was preserved in patientsanaesthetized with propofol–remifentanil (P<0.001).Higher CO₂ concentrations impaired cerebral autoregulation inthe sevoflurane group but not in patients anaesthetized withpropofol–remifentanil. Conclusions. Propofol–remifentanil anaesthesia induceda dose-dependent low-flow state with preserved cerebral autoregulation,whereas sevoflurane at high doses provided a certain degreeof luxury perfusion.