Invasive Monitoring of Cerebral Autoregulation in Aneurysmal Subarachnoid and Intracerebral Hemorrhage: A Systematic Review and Meta-Analysis.

Background: Aneurysmal subarachnoid hemorrhage (aSAH) and spontaneous intracerebral hemorrhage (ICH) are associated with secondary brain injury. Impaired cerebral autoregulation (CA) is hypothesized to be associated with this pathophysiology, reflecting a transition toward a pressure-passive cerebrovascular state. Static clinical variables do not adequately capture this dynamic process, highlighting a potential role for continuous physiological monitoring. Objective: To systematically evaluate the prognostic utility of invasively monitored continuous pressure reactivity index (PRx) and deviation from optimal cerebral perfusion pressure (ΔCPPopt) in adult patients with aSAH and ICH. Methods: A PRISMA-compliant systematic review and meta-analysis was conducted across four major databases. Nineteen studies (13 aSAH, 6 ICH) utilizing continuous invasive monitoring were included. Primary endpoints were mortality and functional recovery; delayed cerebral ischemia (DCI) was a secondary outcome for aSAH. Data were synthesized using random-effects models. Results: In the ICH cohort, elevated mean PRx (Mean Difference [MD] = 0.18; p = 0.005) and deviations below optimal perfusion pressure (ΔCPPopt MD = -6.92 mmHg; p = 0.0001) were associated with unfavorable functional recovery. Furthermore, higher PRx values were significantly associated with mortality (MD = 0.21; p = 0.0006). For aSAH, higher PRx values correlated with poor functional outcomes (MD = 0.10; p = 0.04); however, this association was not robust to sensitivity analysis. Elevated PRx also correlated with DCI occurrence (MD = 0.05; p = 0.04), but the clinical magnitude of this difference remains uncertain. The GRADE certainty of evidence for all assessed outcomes was low, primarily due to the observational design of the included studies and the inherent risk of residual confounding. Conclusions: Low-certainty evidence suggests that continuous monitoring of PRx and ΔCPPopt may offer prognostic utility regarding ischemic complications and functional outcomes in spontaneous brain hemorrhage. While these findings support exploring individualized, autoregulation-guided neurocritical care, prospective multicenter validation remains necessary prior to routine clinical implementation.