Effects of desflurane on cerebral autoregulation

The aim of this study was to determine the effects of desflurane, at 1 and 1.5 MAC, on cerebral autoregulation. Data were analysed from eight patients undergoing non-neurosurgical procedure. The blood flow velocity in the mid dle cerebral artery was measured by transcranial Doppler ultrasound and cer ebral autoregulation was assessed by the transient hyperaemic response test . Partial pressure of the end-tidal carbon dioxide (PE'(CO2)) and mean arte rial pressure were measured throughout the study. Anaesthesia was induced w ith propofol and was maintained with desflurane at end-tidal concentrations of 7.4% (1 MAC) or 10.8% (1.5 MAC). The order of administration of the des flurane concentrations was determined randomly and a period of 15 min was a llowed for equilibration at each concentration. The transient hyperaemic re sponse tests were performed before induction of anaesthesia and after equil ibration with each concentration of desflurane. An infusion of phenylephrin e was used to maintain pre-induction mean arterial pressure and ventilation was adjusted to maintain the pre-induction value of PE'(CO2) throughout th e study. Two indices derived from the transient hyperaemic response test (t he transient hyperaemic response ratio and the strength of autoregulation) were used to assess cerebral autoregulation. Desflurane resulted in a marke d and significant impairment in cerebral autoregulation; at concentrations of 1.5 MAC, autoregulation was almost abolished.