Brain tissue PO 2, PCO 2, and pH during cerebral vasospasm

Abstract

BACKGROUND The purpose of the present study was to assess brain tissue monitoring for detection of ischemia due to vasospasm in aneurysmal subarachnoid hemorrhage (SAH) patients. METHODS After obtaining informed consent, a burr hole was made in 10 patients and a Neurotrend 7 probe was inserted ipsilateral to the region of SAH. In eight patients the probe was inserted during surgery for clipping the aneurysm and in two patients the probe was inserted in the neurosurgery ICU. Brain tissue gases and pH were collected over 6-hour periods for 7 to 10 days until the termination of monitoring. The onset of vasospasm was confirmed by angiography and xenon computed tomography (Xe/CT) cerebral blood flow studies. RESULTS Seven patients did not develop vasospasm during monitoring and were considered as controls. In this group, brain tissue oxygen pressure (PO 2) remained above 20 mmHg, carbon dioxide pressure (PCO 2) stabilized at 40 mmHg and pH remained between 7.1 and 7.2. In three patients who developed vasospasm during monitoring, PO 2 was not different from the control group. However, PCO 2 increased to 60 mmHg and pH decreased to 6.7 ( p < 0.001). CONCLUSION In this study, patients with SAH who developed vasospasm had significantly lower brain tissue pH and higher PCO 2 compared to controls. However, there was no significant change in PO 2 levels associated with vasospasm. Brain tissue monitoring can provide an indication of ischemia during vasospasm.