Assessment of cerebral autoregulation in patients undergoing anaesthesia with propofol: a comparison among spontaneous variability methods

Cerebral autoregulation (CA) is a fundamental homeostatic mechanism that maintains cerebral blood flow (CBF) within a constant range despite blood pressure variations. In this work, two different approaches for assessing CA are compared, i.e. the autoregulation index (ARI) and dynamic entropy measures. The arterial pressure and the CBF velocity were acquired on eighteen subjects undergoing coronary artery bypass graft surgery, before induction of general anaesthesia with propofol and during anaesthesia. The ARI-based method confirmed the known result that CA remains unchanged with propofol. Entropy measures led to complementary findings, suggesting an increased dependence of cerebral blood flow dynamics on systemic pressure, probably due to the effect of mechanical breathing during surgery.