Low intracranial pressure variability is associated with delayed cerebral ischemia and unfavorable outcome in aneurysmal subarachnoid hemorrhage

Purpose High intracranial pressure variability (ICPV) is associated with favorable outcome in traumatic brain injury, by mechanisms likely involving better cerebral blood flow regulation. However, less is known about ICPV in aneurysmal subarachnoid hemorrhage (aSAH). In this study, we investigated the explanatory variables for ICPV in aSAH and its association with delayed cerebral ischemia (DCI) and clinical outcome. Methods In this retrospective study, 242 aSAH patients, treated at the neurointensive care, Uppsala, Sweden, 2008-2018, with ICP monitoring the first ten days post-ictus were included. ICPV was evaluated on three time scales: (1) ICPV-1 m-ICP slow wave amplitude of wavelengths between 55 and 15 s, (2) ICPV-30 m-the deviation from the mean ICP averaged over 30 min, and (3) ICPV-4 h-the deviation from the mean ICP averaged over 4 h. The ICPV measures were analyzed in the early phase (day 1-3), in the early vasospasm phase (day 4-6.5), and the late vasospasm phase (day 6.5-10). Results High ICPV was associated with younger age, reduced intracranial pressure/volume reserve (high RAP), and high blood pressure variability in multiple linear regression analyses for all ICPV measures. DCI was associated with reduced ICPV in both vasospasm phases. High ICPV-1 m in the post-ictal early phase and the early vasospasm phase predicted favorable outcome in multiple logistic regressions, whereas ICPV-30 m and ICPV-4 h in the late vasospasm phase had a similar association. Conclusions Higher ICPV may reflect more optimal cerebral vessel activity, as reduced values are associated with an increased risk of DCI and unfavorable outcome after aSAH.