Dynamic Cerebral Autoregulation in Patients with Ruptured and Unruptured Aneurysms after Induction of General Anesthesia

Abstract

Blood pressure management in patients undergoing surgery for clipping of aneurysms is demanding. More information about the ability of cerebral vessels to normally regulate cerebral blood flow may have a direct influence on the intraoperative management. In patients with subarachnoid hemorrhage (SAH) a disturbance of cerebral autoregulation has been reported and it correlated with the severity of the bleeding in these studies. The impairment of autoregulation was demonstrated using static measurements of cerebral pressure autoregulation. However, the dynamic component of the autoregulatory capacity seems to be of importance in the acute setting after SAH. The aim of this study was to evaluate dynamic pressure autoregulation in patients undergoing surgery for intracranial aneurysms. 36 patients with a mean age of 45 years were evaluated, 26 patients with acute SAH, 10 patients with unruptured aneurysms. Cerebral autoregulation in normocapnia was tested using thigh cuffs to alter arterial blood pressure and continuous registration of the blood flow velocities with transcranial Doppler sonography. After the induction of general anesthesia under normocapnia the autoregulatory index (ARI) was calculated (values between 0-9). Patient groups were compared using Wilcoxon- and Spearman's rank test. The two patient groups were comparable with regard to gender, age, PaCO(2), blood flow velocities and blood pressure. In patients with SAH mean ARI was 3.1/3.3 (right/left side) compared to 4.7/4.6 (right/left side) in patients without SAH. The difference was statistically significant (Wilcoxon p = 0.0399). The degree of impairment of the autoregulatory capacity increased significantly (p = 0.006) with the severity of the SAH (Hunt&Hess and Fisher scale). Dynamic pressure autoregulation is impaired in patients after SAH compared to patients without SAH and correlates with the severity of the SAH. We propose that autoregulation should be measured in all patients with SAH or that an impaired autoregulation should be taken into account in patients with SAH undergoing surgery in the acute phase.