Strength and Latency of Mean Cerebral Blood Flow Velocity and Mean Arterial Pressure Coupling during Propofol General Anesthesia in Subjects Undergoing Coronary Artery Bypass Graft

Cerebral autoregulation (CA), namely the mechanism aiming at maintaining mean cerebral blood flow (MCBF) constant in spite of variations of mean arterial pressure (MAP), was investigated by means of cross-correlation function (CCF) between MCBF velocity (MCBFV) and MAP in subjects undergoing coronary artery bypass grafting before (PRE) and after (POST) the induction of propofol anesthesia. The null hypothesis of coupling was tested via a surrogate approach over the CCF minima and maxima detected at lags closest to 0. Both positive and negative lags were considered and monitored in correspondence of the considered CCF values. Results suggest that MCBFV and MAP were significantly associated during both PRE and POST but the maximal positive association was reduced in POST and occurred more likely at 0 lag during POST than PRE. Further studies are needed to understand whether the reduced MCBFV-MAP positive association and time shift implies the maintenance of a suitable CA level during propofol anesthesia.