Objective:

Determine the relationship between cerebral autoregulation, quantitative electroencephalography, and their effect on outcomes in aneurysmal subarachnoid hemorrhage (aSAH).

Background:

Deviations from personalized blood pressure targets have been associated with an increased risk of delayed cerebral ischemia (DCI) and worse functional outcomes after aSAH. Quantitative EEG also effectively predicts complications after aSAH. However, the pathophysiologic mechanisms underlying these complications and potential interactions between these two parameters remain unclear. 

Design/Methods:

We included patients with aSAH who were simultaneously monitored with continuous EEG, blood pressure and near-infrared spectroscopy. Autoregulatory function was measured by analyzing changes in regional oxygen saturation in response to changes in mean arterial pressure. The resulting autoregulatory index was utilized to determine and monitor the limits of autoregulation in each patient.  EEG band powers, alpha delta ratio, and relative alpha variability were calculated approximating anterior, middle, and posterior cerebral artery territories.   

Results:

Forty-one patients (mean age 55 ±14 years, 68% female, Hunt Hess 3.1±0.9, modified Fisher 3.6 ±0.6) were monitored for a mean duration of 137 ±94 hours. Patients who developed DCI spent more time outside the limits (mean 20.7 ±9.8%) than those who did not (13.8 ±7.7%, p<0.005). Time outside the limits of autoregulation was linked to worse outcomes at discharge (OR per 10%: 2.4, p=0.022) and at 90 days (OR per 10%: 2.5, p=0.015). Decreased ADR was also associated with worse outcome at discharge (OR per 0.1: 1.78, p=0.043) and 90 days (OR per 0.1: 1.80, p=0.041). No significant difference was found in quantitative EEG parameters when blood pressure was below versus within autoregulation limits.

Conclusions:

Time spent outside autoregulation limits and ADR are associated with worse outcomes after aSAH, but ABP drops below the lower limit did not consistently affect ADR. Further analyses are underway to elucidate the interactions between cerebral autoregulation, neurophysiology, and outcomes.