gms | German Medical Science

Objective: Measurement of regional cerebral oxygen saturation (rSO₂) with near infrared spectroscopy (NIRS) is used frequently during cardiac and vascular surgeries. However, continuous measurement for detecting cerebral vasospasm (CVS) after SAH is not done consistently. The aim of our prospective study was to investigate the applicability and the diagnostic value of NIRS in SAH patients using the cerebral oximeter INVOS 5100C (Sommanetics).

Methods: After diagnosis of SAH and following treatment of the bleeding source, self-adhesive oximetry strips were applied bilaterally to the forehead to measure continuously the baseline value of rSO₂ in 3 cm depth. Decrease of rSO₂ was analyzed and interpreted in view of the determined intrinsic and extrinsic factors (mean arterial blood pressure, hemoglobin, peripheral oxygen saturation, partial carbon dioxide pressure, core temperature, head positioning, correct position and adhesion of the strips). Changes of rSO₂ values were matched with the values of intracerebral pressure (ICP), partial brain tissue oxygen saturation (tipO₂), transcranial Doppler (TCD) and the results of additional neuro-imaging.

Results: Continuous measurement of rSO₂ was performed in nine patients with SAH (7 female, 2 male). Mean measurement time was 8.6 days (range 2–12 days). The clinical course was uneventful in 7 patients without occurrence of CVS. In these patients NIRS measured constant and stable rSO₂ values without any decrease in agreement with the values of TCD, ICP and tipO₂. Special findings were observed in 2 cases. In one case NIRS detected early a right sided decrease of cerebral oxygenation below the critical value of 45%. TCD showed elevated flow velocities over the middle and anterior cerebral artery, but perfusion-CT scan showed normal patterns. Despite forced triple-H therapy the patient developed a right frontal lobe stroke with increase of ICP. In the other case, TCD showed elevation of flow velocities and DSA showed radiological CVS. However, NIRS showed continuously normal values and the patient developed no CVS related stroke.

Conclusions: Measurement of rSO₂ with NIRS is a safe, easy to use, non-invasive additional measurement tool for CVS after SAH and can be applied over a long time period, especially for conscious patients, presumed the involved nursing personnel is instructed. Our study demonstrates the applicability of the INVOS 5100C and the measured values seem to be reliable. However, further large studies are needed to prove our first observations.