A comparison of propofol and sevoflurane anaesthesia: Effects on aortic blood flow velocity and middle cerebral artery blood flow velocity

We compared systemic (aortic) blood flow and cerebral blood flow velocity in 30 patients randomly allocated to receive either propofol or sevoflurane anaesthesia. Cerebral blood flow velocity (CBFv) was measured in the middle cerebral artery using transcranial Doppler. Systemic blood flow velocity (SBFv) was measured in the aorta using transthoracic Doppler sonography at the level of the aortic valve. Bispectral index (BIS) was used to measure the depth of anaesthesia. Measurements were made in the awake patient and repeated during propofol or sevoflurane anaesthesia, with BIS measurements of 40-50. The effects of SBFv on CBFv were estimated by calculating the cerebral/systemic blood flow velocity-index (CsvI). A CsvI value of 100 indicating a 1 : 1 relationship between CBFv and SBFv. The results demonstrated that propofol anaesthesia produced a significantly greater reduction in CsvI than did sevoflurane anaesthesia [propofol: 60 (19); sevoflurane: 83 (16), p = 0.009, t-test]. This suggests a direct reduction in CBFv independent of SBFv during propofol anaesthesia. The greater reduction of CBFv occurring during propofol anaesthesia may be due to lower cerebral metabolic demand compared with sevoflurane anaesthesia at comparable depths of anaesthesia.