P52. Clinical use of non-invasive intraoperative neuromonitoring to detect changes in local cerebral microcirculation

Question Are intraoperatively acquired parameters of pathological cortical microcirculation predictive of postoperative clinical outcome? Methods In 5 patients (Hunt & Hess grade III–V) suffering from subarachnoid hemorrhage due to an cerebral aneurysm, local cerebral microcirculation was measured intraoperatively using the novel non-invasive laser-Doppler spectrophotometry system “Oxygen-to-see (O2C)”. A subdural fiber optic probe was placed on the distal supply territory of the aneurysmatic blood vessel. Monitoring of capillary venous oxygenation (SO2), post-capillary venous filling pressures (rHb), blood cell velocity (velo) and blood flow (flow) was performed in 7 mm tissue depth. Additionally, we monitored somatosensory evoked potentials (SEP) by stimulation of the median nerve and posterior tibial nerve according to the specific anatomic site. Results All aneurysms (MCA: 2, AcomAnt: 2, ACA: 1) were treated successfully by microsurgical clipping. Measurements showed a diminished blood flow and velocity, increased rHb and SO2 in all cases. Corresponding N20 and P40 waves showed an increase in latency and decrease in amplitude. Postoperatively, all patients had neurological deficits. Conclusions Preliminary results of this novel method measuring local cortical microcirculation indicate that there may be a correlation between intraoperative parameter changes and the postoperative clinical course. Comparison with the standard method of SEP-monitoring also coincides with clinical outcome. The combined laser-Doppler flowmetry and spectrophotometry system gives real-time information on local blood supply, which may lead to an improved prediction of brain edema, vasospasm, or cerebral infarction. Larger patient numbers are needed to confirm these observations and their predictive value.