437 Pressure Reactivity Index (PRx) as a Predictor for Outcome in Severe Traumatic Brain Injury

INTRODUCTION: The pressure reactivity index (PRx) is a surrogate for vascular cerebral autoregulation that evaluates moving correlation coefficients between intracranial pressure (ICP) and mean arterial blood pressure (MAP). Ideal threshold PRx values for distinguishing between poor and good outcome in severe traumatic brain injury (sTBI) is unclear. METHODS: Retrospective evaluation of consecutive patients over a three-year period with sTBI and polytrauma who received continuous ICP, MAP, and PRx monitoring. Good outcome was defined as patients who upon hospital discharge had a modified Rankin score < 4 and were discharged to an acute rehabilitation facility or home. RESULTS: 36 patients received continuous monitoring. Nine patients were excluded for the following reasons: early palliative withdrawal, early death through multi-organ dysfunction not related to the sTBI, and continuous neuromonitoring < 24 hrs. Of the 27 patients evaluated, average PRx values for the good outcome group was 0.18 (+0.17) and 0.37 (+0.24) for the poor outcome group. Receiver operating characteristics (ROC) analysis showed that a PRx threshold value > 0.34 had the highest combined sensitivity and specificity for predicting poor outcome with an AUC (95% CI) = 0.775 (0.583-0.967). When dichotomized using ROC curve analysis, a threshold PRx value of greater than 0.34 was independently associated with higher odds of poor outcome (OR 18.63, 95% CI 1.17-297.21, p = 0.038) after adjustment for potential confounders. CONCLUSIONS: Higher mean PRx is an independent predictor for poor outcome in patients with sTBI. Further study is required to evaluate the temporal role of PRx changes to improve neuroprognostication.