Optimal mean arterial pressure based on cerebrovascular autoregulation during and after non-cardiac surgery

Abstract

Background: Cerebrovascular autoregulation (CVA) maintains steady cerebral brain blood flow despite changes in perfusion pressure, a mechanism which is crucial during surgery and anaesthesia. Perioperative measurement of CVA allows for the determination of CVA-based optimal mean arterial blood pressure (MAPopt), which is defined as the blood pressure at which the CVA reaches maximal activity. The aim of this study was to compare intra- and postoperative CVA-based MAPopt and time-weighted average (TWA)-MAP below the CVA-based MAPopt. In addition, this study aimed to assess factors associated with intra- and postoperative TWA-MAP below the CVA-based MAPopt. Methods: This sub-study of an ongoing single-centre prospective cohort study was conducted between August 2021 and May 2022. Adult patients scheduled for non-cardiac surgery of >120 minutes with general anaesthesia, invasive blood pressure monitoring and pre-existing anaemia or expected blood loss >500ml were enrolled. CVA was assessed through correlation between MAP and regional cerebral oxygen saturation detected by near-infrared spectroscopy. Each patient was assessed intra- and postoperatively. CVA-based MAPopt was defined as MAP with the lowest correlation with cerebral oxygen saturation . TWA-MAP was calculated as the area between the MAP and the MAPopt curve, normalized to the duration of CVA assessment. Factors associated with the intra- and postoperative TWA-MAP below the CVA-based MAPopt were analysed using multivariable general linear models. Results: The final analysis included 161 patients. The median intra- and postoperative CVA-based MAPopt differed significantly (77.85 (IQR: 72.78, 84.13) mmHg versus 85.10 (IQR: 77.91, 95.06) mmHg, p < 0.001). The median intra- and postoperative TWA-MAP below the CVA-based MAPopt did not differ significantly (2.59 (IQR: 0.93, 5.41) mmHg versus 4.26 (IQR: 1.06, 8.73) mmHg, p = 0.118). Propofol for anaesthesia maintenance was associated with a larger intraoperative TWA-MAP below the CVA-based MAPopt. Conclusion: Intraoperative CVA-based MAPopt is lower than postoperative CVA-based MAPopt, which might require different blood pressure management in different perioperative periods. The application of propofol for anaesthesia maintenance and major abdominal surgery are associated with lower intraoperative MAP.