253 Tissue Partial Pressure of Oxygen During Spreading Depolarization in Malignant Stroke is Associated With Outcome

INTRODUCTION: Spreading depolarization (SD) describes a propagating neuronal mass depolarization within the cerebral cortex that likely represents a relevant mechanism of secondary lesion progression. METHODS: This prospective observational study included 25 patients with MHS that underwent decompressive hemicraniectomy (DC) followed by subdural placement of an electrocorticography (ECoG) strip electrode and cortical implantation of a PtiO2 probe within in the periinfarct tissue. Continuous ECoG and PtiO2 recordings were obtained at bedside for five days and analyzed for the occurrence of SD and SD-associated PtiO2 changes, as well as their association with clinical outcome at 6 months. RESULTS: The overall simultaneous ECoG and PtiO2 recording time was 2603 hours, during which 796 SDs were detected. The overall SD duration and SD frequency did not correlate with outcome. During the observation period, the overall PtiO2baseline changed significantly with an almost linear increase that reached a peak around 100 hours (*p=0.0055), followed by a PtiO2 drop until the end of the monitoring period (*p = 0.0048). Accordingly, low baseline PtiO2 (<15 mmHg) was mainly noted during the first 24 hours but did not correlate with outcome (p = 0.916). Conversely, 20 out of 25 patients showed SD-associated PtiO2 changes in 363 out of 796 SDs (45.6%), which were categorized as biphasic (222), hypoxic (119) and hyperoxic (22). Among these SD-associated PtiO2 responses, a high occurrence rate, biphasic response pattern and high amplitude correlated significantly with favorable outcome (mRS 1-3) at 6 months. CONCLUSIONS: SD-associated PtiO2 coupling in patients suffering hemispheric stroke appears to be associated with clinical outcome and could reflect the presence of viable and metabolically less impaired peri-infarct tissue.