Hypoxic brain tissue following subarachnoid hemorrhage.

BACKGROUND

Subarachnoid hemorrhage can lead to cerebral ischemia and irreversible brain injury. The purpose of this study was to determine whether subarachnoid hemorrhage produces changes in brain tissue oxygen pressure, carbon dioxide pressure, or pH during surgery for cerebral aneurysm clipping.

METHODS

After institutional review board approval and patient consent, 30 patients undergoing craniotomy for cerebral aneurysm clipping were studied, 15 without and 15 with subarachnoid hemorrhage. Patients with subarachnoid hemorrhage were prospectively separated into groups with modest (Fisher grade 1 or 2; n = 8) and severe bleeds (Fisher grade 3; n = 7). After a craniotomy, a probe was inserted into cortex tissue supplied by the artery associated with the aneurysm. Baseline measures were made in the presence of a 4% end-tidal desflurane level. The end-tidal desflurane level was increased to 9% before clipping of the aneurysm, and a second tissue measurement was made.

RESULTS

The median time of surgery after subarachnoid hemorrhage was 2 days, ranging from 1 to 13 days. During baseline anesthesia, brain tissue oxygen pressure was 17+/-9 mm Hg (mean +/- SD) in control patients, 13+/-9 mm Hg in those with Fisher grade 1 or 2 hemorrhage, and 7+/-6 mm Hg in those with Fisher grade 3 hemorrhage (P<0.05 compared with control). Brain tissue pH was 7.10+/-0.10 in control patients, 7.14+/-0.13 in those with Fisher grade 1 or 2 hemorrhage, and 6.95+/-0.18 in those with with Fisher grade 3 hemorrhage (P<0.05). At a 9% end-tidal desflurane level, brain tissue oxygen pressure increased to 19+/-9 mm Hg and brain tissue pH increased to 7.11+/-0.11 in patients with Fisher grade 3 hemorrhage (P<0.05 for both increases).

CONCLUSION

These results show that subarachnoid hemorrhage can significantly decrease brain tissue oxygen pressure and pH related to the severity of the bleed. Increasing the desflurane concentration to 9% increased brain tissue oxygen pressure in all patients and brain tissue pH in patients with subarachnoid hemorrhage with baseline acidosis.