Abstract 4037: Dynamic Cerebral Autoregulation in Patients with Subarachnoid Hemorrhage and Delayed Cerebral Ischemia

Abstract

Introduction: We have previously shown that early impairments in dynamic cerebral autoregulation are strongly associated with subsequent development of angiographic cerebral vasospasm. While angiographic cerebral vasospasm is associated with delayed cerebral ischemia (DCI), the relationship between cerebral autoregulation and DCI has not been previously investigated. Our study is designed to specifically test the relationship between early changes in dynamic cerebral autoregulation and subsequent development of DCI. Methods: Thirty-nine consecutive patients with acute non-traumatic subarachnoid hemorrhage (SAH) and adequate transcranial Doppler windows, presenting within 24 hours of symptom onset, have been prospectively studied so far. Daily 5-minute measures of continuous beat-to-beat bilateral middle cerebral artery (MCA) flow velocity and mean arterial blood pressure (MAP) recordings were obtained on days 1-10. Transfer function analysis of spontaneous MAP and MCA mean flow velocity (MFV) oscillations were performed in the very low (0.03-0.07 Hz), low (0.07-0.15 Hz), and high (0.15-0.3 Hz) frequency ranges. Non contrast head CTs were reviewed by a neurologist and neuroradiologist blinded to the autoregulatory and angiographic data. Infarctions present within 6 weeks after SAH, which could not be attributed to instrumentation or peri-op strokes, were identified as DCI. Results: Patients with DCI had significantly higher Hunt and Hess (H&H) scores (median=4 vs 3, p<0.0001) compared to those without DCI. There was no difference in MAP (p=0.746), right MCA (p=0.8327)) or left MCA MFV (p=0.4278) between patients with and without DCI across all time points. Patients with DCI had a lower transfer function phase in the very low frequency (autoregulatory frequency) range. Subgroup analysis of patients with H&H scores ≥3 (N=14) showed that those with DCI had significantly lower phases on day 3 compared to those without DCI (-13±80 vs. 63±26, p=0.048). Conclusion: Our preliminary data show that dynamic cerebral autoregulation, as measured by transfer function phase in the autoregulatory frequency range, is significantly impaired in the early days after SAH and that this early impairment is associated with the development of DCI. We are continuing to collect data on additional patients with SAH to confirm our findings in a larger cohort. Impairments in dynamic cerebral in the early days post SAH may be reliable predictors for identifying patients at higher risk of delayed cerebral ischemia.