Testing the involvement of baroreflex during general anesthesia through Granger causality approach

Baroreflex sensitivity (BRS) is commonly assessed from spontaneous fluctuations of heart period (HP) and systolic arterial pressure (SAP) during general anesthesia. Unfortunately, general anesthesia depresses autonomic function and, consequently, spontaneous SAP variations could not be capable to drive HP changes, thus preventing the use of spontaneous variability to infer BRS. We applied two Granger causality approaches (F-test and Wald test) during two anesthesiological strategies (i.e. sevoflurane plus remifentanil or propofol plus remifentanil). We found a significant Granger-causality from SAP to HP independently of the anesthesiological strategy; thus suggesting that techniques estimating BRS from spontaneous variability can be utilized during general anesthesia.