Dynamic three-dimensional scoring of cerebral perfusion pressure and intracranial pressure provides a brain trauma index that predicts outcome in patients with severe traumatic brain injury

Background: Data on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) guide therapy in severe traumatic brain injury (TBI), but current linear analytic methods are insufficiently sensitive and specific for prognosis in dynamic situations over time.

Methods: We have developed algorithms incorporating continuous, automated, digital ICP and CPP monitoring data into a pressure times time "dose" function. In this study, we calculated cumulative doses using thresholds of ICP >20 mm Hg and CPP <60 mm Hg and graphed these as a Brain Trauma Index (BTI or CPP/ICP). Using receiver operator characteristics analysis, we examined BTI <3 and BTI <2 and various threshold levels of pressure times time doses of ICP and CPP as predictors of 30-day mortality and Extended Glasgow Outcome Scale (GOSE) <5 at 6 months and 12 months. Using the data processing and analysis tools underlying this work, we are also piloting a real-time bedside and telemetric display system as a means of indentifying and monitoring critical changes in physiologic metrics, including BTI, CPP, and ICP.

Results: Sixty subjects yielded 8678.1 hours of data (5,206,860 data points). BTI <2 was better than CPP <60 mm Hg in predicting unfavorable Extended Glasgow Outcome Scale at 6 months (p <0.05). An example of linear and graphically processed BTI, CPP, and ICP data from a representative TBI patient is provided.

Conclusion: Calculation of a BTI from continuous digital data predicts outcome in severe TBI and has potential for the design of real-time bedside early warning systems.