Bedside Monitoring of Cerebral Blood Oxygenation and Hemodynamics after Aneurysmal Subarachnoid Hemorrhage by Quantitative Time-Resolved Near-Infrared Spectroscopy

BACKGROUND: Early detection of vasospasm is essential for the treatment of delayed ischemic neurological deficits in subarachnoid hemorrhage (SAH). We evaluated cerebral blood oxygenation (CBO) changes after SAH employing quantitative time-resolved near-infrared spectroscopy (TR-NIRS) for this purpose. METHODS: We investigated 11 age-matched controls and 14 aneurysmal SAH patients, including 10 patients with WFNS grade V and 4 patients with grade II. Employing TR-NIRS, we measured the cortical oxygen saturation (CoSO(2)) and baseline hemoglobin concentrations in the middle cerebral artery territory. Measurements of TR-NIRS and transcranial Doppler sonography (TCD) were performed repeatedly after SAH. RESULTS: In six patients, the CoSO(2) and hemoglobin concentrations remained stable after SAH; digital subtraction angiography (DSA) did not reveal vasospasm in these patients. In eight patients, however, CoSO2 and total hemoglobin decreased abruptly between 5 and 9 days after SAH. DSA revealed diffuse vasospasms in six of eight patients. The reduction of CoSO(2) predicted occurrence of vasospasm at a cutoff value of 3.9%-6.4% with 100% of sensitivity and 85.7% of specificity. TCD failed to detect the vasospasm in four cases, which TR-NIRS could detect. Finally, TR-NIRS performed on Day 1 after SAH revealed significantly higher CoSO(2) than that of controls (p = .048), but there was no significant difference in total hemoglobin. CONCLUSION: TR-NIRS detected vasospasm by evaluating the CBO in the cortex and may be more sensitive than TCD, which assesses the blood flow velocity in the M1 portion. The cerebral oxygen metabolism in SAH might be reduced by brain damage due to aneurysmal rupture.