Pressure reactivity index for early neuroprognostication in poor-grade subarachnoid hemorrhage.

BACKGROUND:Pressure reactivity index (PRx) utilizes moving correlation coefficients from intracranial pressure (ICP) and mean arterial pressures to evaluate cerebral autoregulation. We evaluated patients with poor-grade subarachnoid hemorrhage (SAH), identified their PRx trajectories over time, and identified threshold time points where PRx could be used for neuroprognostication. METHODS:Patients with poor-grade SAH were identified and received continuous bolt ICP measurements. Dichotomized outcomes were based on ninety-day modified Rankin scores and disposition. Smoothed PRx trajectories for each patient were created to generate "candidate features" that looked at daily average PRx, cumulative first-order changes in PRx, and cumulative second-order changes in PRx. "Candidate features" were then used to perform penalized logistic regression analysis using poor outcome as the dependent variable. Penalized logistic regression models that maximized specificity for poor outcome were generated over several time periods and evaluated how sensitivities changed over time. RESULTS:16 patients with poor-grade SAH were evaluated. Average PRx trajectories for the good (PRx < 0.25) and poor outcome groups (PRx > 0.5) started diverging at post-ictus day 8. When targeting specificities ≥88% for poor outcome, sensitivities for poor outcome consistently increased to >70% starting at post-ictus days 12-14 with a maximum sensitivity of 75% occurring at day 18. CONCLUSIONS:Our results suggest that by using PRx trends, early neuroprognostication in patients with SAH and poor clinical exams may start becoming apparent at post-ictus day 8 and reach adequate sensitivities by post-ictus days 12-14. Further study is required to validate this in larger poor-grade SAH populations.