Hypotension After Cardiac Operations Based on Autoregulation Monitoring Leads to Brain Cellular Injury

This is a provocative study questioning the current practice of using blood pressure targets perioperatively to ensure adequate perfusion.  Plasma levels of a brain-specific injury biomarker (GFAP) were measured in 121 patients undergoing cardiac surgery.  The cerebral oximetry index, which correlates changes in mean arterial pressure (MAP) and regional cerebral oxygen saturation, was used to define individualized optimal MAPs.  A comparison was made correlating the degree of cerebral injury as measured by GFAP levels and either conventional MAP targets or oximetry-based targets defining hypotension.  The incidence of hypotension varied from 22-37% by conventional definitions, but the incidence was much higher at 54% when using the cerebral oximetry index.  Whereas oximetry-derived hypotension correlated with GFAP levels on POD 1, conventional hypotension did not.