Intraoperative monitoring of cerebral blood oxygenation and hemodynamics during extracranial-intracranial bypass surgery by a newly developed visible light spectroscopy system.

BACKGROUND Cerebrovascular reconstruction procedures run the risk of changing the balance between oxygen supply and consumption during surgery. We assessed the value of visual light spectroscopy for detecting changes in cerebral blood oxygenation (CBO) during superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis. METHODS We developed a VLS monitoring system which permits continuous monitoring of CBO changes during surgery. Using the VLS, we evaluated the CBO changes in the MCA territory on the lesion side in 18 patients who underwent STA-MCA anastomosis. RESULTS Temporary occlusion of the MCA (M4 portion) did not change the CBO in 17 patients. However, in the patient with dissecting aneurysm, it caused decreases of oxyhemoglobin and cortical oxygen saturation (CoSo(2)) associated with an increase of deoxyhemoglobin, although these CBO changes were normalized by STA blood flow. In 5 patients, STA blood flow increased the oxyhemoglobin and CoSo(2) and decreased the deoxyhemoglobin, indicating that cortical blood flow (CoBF) was increased. The CoSo(2) before anastomosis was significantly low in the patients who showed an increase of CoSo(2) by STA blood flow (63.0% +/- 2.5%) as compared with those who did not (72.0 +/- 6.1%, P = .024). CONCLUSION Temporary occlusion of a cortical artery during bypass surgery did not affect the CBO in patients who had chronic cerebral ischemia, but caused acute ischemia in the patient who did not. STA blood flow increased the CoBF during surgery more frequently in patients who showed a low perfusion pressure. The VLS monitoring system is considered useful for evaluating bypass function and facilitates safe and accurate bypass surgery.