• Ulf Johnson, Henrik Engquist, Tim Howells, Pelle Nilsson, Elisabeth Ronne-Engström, Anders Lewén, Elham Rostami, and Per Enblad.
• Department of Neuroscience/Neurosurgery, Uppsala University, Uppsala, Sweden. ulf.johnson@neuro.uu.se.
• Neurocrit Care. 2016 Aug 1; 25 (1): 47-55.

BackgroundSubarachnoid hemorrhage (SAH) is a disease with a high rate of unfavorable outcome, often related to delayed cerebral ischemia (DCI), i.e., ischemic injury that develops days-weeks after onset, with a multifactorial etiology. Disturbances in cerebral pressure autoregulation, the ability to maintain a steady cerebral blood flow (CBF), despite fluctuations in systemic blood pressure, have been suggested to play a role in the development of DCI. Pressure reactivity index (PRx) is a well-established measure of cerebral pressure autoregulation that has been used to study traumatic brain injury, but not extensively in SAH.ObjectiveTo study the relation between PRx and CBF in SAH patients, and to examine if PRx can be used to predict DCI.MethodsRetrospective analysis of prospectively collected data. PRx was calculated as the correlation coefficient between mean arterial blood pressure (MABP) and intracranial pressure (ICP) in a 5 min moving window. CBF was measured using bedside Xenon-CT (Xe-CT). DCI was diagnosed clinically.Results47 poor-grade mechanically ventilated patients were studied. Patients with disturbed pressure autoregulation (high PRx values) had lower CBF, as measured by bedside Xe-CT; both in the early (day 0-3) and late (day 4-14) acute phase of the disease. PRx did not differ significantly between patients who developed DCI or not.ConclusionIn mechanically ventilated and sedated SAH patients, high PRx (more disturbed CBF pressure autoregulation) is associated with low CBF, both day 0-3 and day 4-14 after onset. The role of PRx as a monitoring tool in SAH patients needs further studying.

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