ABSTRACT NUMBER: ESOC2026YS227 ENDOVASCULAR HYPOTHERMIA FOR HIGH-GRADE ANEURYSMAL SUBARACHNOID HEMORRHAGE (EHASH): A PHASE 1 PILOT STUDY OF TARGETED COOLING AS NEUROPROTECTION

Abstract Background and aims High-grade aneurysmal subarachnoid hemorrhage (aSAH) carries high mortality and disability, driven by secondary injury processes such as cerebral edema, vasospasm, and delayed cerebral ischemia. Prior small studies suggest that controlled endovascular hypothermia may attenuate these cascades and improve outcomes, but protocolized data in high-grade aSAH are limited. EHASH aims to evaluate the safety, feasibility, and preliminary neuroprotective signals of early, time-limited endovascular hypothermia in high-grade aSAH.​ Methods EHASH is a prospective, single-arm, phase 1 pilot study enrolling adults with high-grade aSAH (WFNS IV–V) within 6 hours of last-known-well after aneurysm securing by clipping or coiling. An endovascular cooling catheter (ZOLL, Chelmsford, MA) will be placed via a femoral venous sheath to achieve a target core temperature of 33°C for 3–6 hours, followed by controlled rewarming at 0.5°C every 12 hours. Primary endpoints are safety and feasibility (catheter- or cooling-related complications; proportion achieving and maintaining target temperature). Secondary endpoints include cerebral edema, vasospasm, CSF inflammatory biomarkers, and functional outcomes (modified Rankin Scale at discharge and 90 days), compared with historical controls.​ Results The protocol and multidisciplinary infrastructure have been developed, and the team is actively seeking internal and external funding to initiate the study. Upon funding, regulatory approvals and catheter procurement will proceed, with planned enrolment of 10–15 patients to generate safety, feasibility, and preliminary efficacy data to inform a future multicenter study in high-grade aSAH.​ Conflict of interest 1. Archit Baskaran - nothing to disclose 2. Rami Z Morsi - nothing to disclose 3. Shyam Patel - nothing to disclose 4. Julia Iourinets - nothing to disclose 5. Alireza Borghei - nothing to disclose 6. Jorie Singer - nothing to disclose 7. Sophia Haggerty - nothing to disclose 8. Tareq Kass-Hout - nothing to disclose