2014 Volume 25 Issue 2 Pages 31-36
Cerebrovascular autoregulation is the process whereby an elevation of systemic blood pressure is counteracted by a reduction in the volume of the cerebrovascular beds in order to maintain a consistent level of cerebral blood flow (CBF). This reduction in the cerebrovascular bed volume subsequently causes a reduction in intracranial pressure (ICP); therefore, ICP is negatively correlated with systemic blood pressure. Cases of severe brain damage with dysfunctional cerebrovascular autoregulation show elevated ICP along with increased blood pressure, which means that a positive correlation exists between both parameters. The pressure reactivity index (PRx) is a moving correlation coefficient between the mean arterial blood pressure (MABP) and ICP, and has recently been reported to be useful for clinical monitoring of patients with severe subarachnoid hemorrhage (SAH) and traumatic brain injury. In this study, we investigated the preservation of cerebrovascular autoregulation using PRx monitoring in patients with poor grade SAH. Ten patients with severe aneurysmal SAH were recruited; the mean age was 65.0 ± 12.0, and the mean value of the Glasgow Coma Scale (GCS) score was 4.3 ± 1.7. All patients had a grade V for the World Federation of Neurosurgeons (WFNS) score. Three of the ten cases underwent open surgery consisting of neck clipping of the ruptured cerebral aneurysm. The remaining patients underwent coil embolization of the ruptured aneurysms. Decompressive hemicraniectomy was also achieved for five cases, in an effort to control intracranial hypertension. Three months after the onset of SAH, two cases had favorable outcomes for Good Recovery (GR) and Moderately Disabled (MD) on the Glasgow Outcome Scale (GOS), while the other eight cases had unfavorable outcomes, including one death. The mean value of PRx during the acute stage was 0.047 ± 0.0002 in the favorable outcome cases, and 0.230 ± 0.184 in the unfavorable outcome cases. Cerebral vasomotor reaction resulted in a reduced response in the unfavorable outcome group, and this result was considered to reflect a strong positive correlation between ICP and MABP in the unfavorable outcome group. In six patients with delayed cerebral infarction following cerebral vasospasm after SAH, the mean value of PRx during the acute stage was 0.309 ± 0.13, while it was 0.019 ± 0.03 in the other 4 patients without cerebral infarction. Statistical analysis showed a significant difference in the PRx value between the patients with delayed cerebral infarction and the others (p<0.05). We discuss the usefulness of PRx monitoring, taking into consideration the available literature.
