Abstract Body: Background: Impaired cerebral autoregulation has been linked to worse outcomes following aneurysmal subarachnoid hemorrhage (aSAH). Delayed cerebral ischemia and vasospasm are critical complications of aSAH, and intra-arterial (IA) verapamil can be employed as pharmacologic spasmolysis in severe or refractory cases. However, the impact of this treatment on cerebral hemodynamics and blood flow autoregulation remains unknown.

Methods: We evaluated near-infrared spectroscopy (NIRS) and mean arterial pressure (MAP) recordings from aSAH patients who underwent angiography with infusion of IA verapamil for anterior circulation vasospasm. NIRS-derived regional oxygen saturation (rSO2) from the affected hemisphere was correlated with MAP to derive the optimal blood pressure (MAP_OPT) at which cerebral autoregulation was the most preserved, as well as the associated lower and upper limits of autoregulation (LA). Hemodynamic and autoregulatory parameters were compared at three 24-hour intervals: baseline, before, and after intervention. Data were excluded if there were fewer than 6 hours of calculated autoregulatory parameters in any of the three epochs or greater than 4 hours between data availability and the intervention start or end.

Results: The study included 27 interventions (mean verapamil dose 24 ± 10 mg, monitoring time 19.7 ± 3.5 hours per 24-hour period) across 15 patients (mean age 56 ± 11 years, 40% female, Hunt Hess 3.4 ± 0.9, modified Fisher 4 ± 0). From baseline (6.4 ± 3.8 days prior to intervention) to the time of intervention, there was a significant increase in actual MAP, MAP_OPT, and LA (p<0.001), accompanied by a decrease in rSO2 (p=0.001, Table 1). Following intervention, the time spent above the upper limit of autoregulation decreased from 17.1 ± 2.3% to 12.1 ± 1.7% (p=0.02), while autoregulatory parameters and tissue oxygenation remained stable. Sensitivity analysis limited to the first intervention for each patient confirmed similar findings.

Conclusions: Our analysis demonstrated a decrease in tissue oxygenation and an increase in limits of autoregulation from baseline to the time when intervention was performed for vasospasm post-aSAH. IA verapamil administration was associated with a reduction in time spent above the upper limit of autoregulation, suggesting that pharmacologic spasmolysis for severe or refractory vasospasm may lead to improvement in autoregulatory physiology. Further exploratory analyses are ongoing.