Abstract Body: Background
We aimed to evaluate whether the implementation of regional prehospital transport to comprehensive stroke center (CSC) protocol has any impact on inter-hospital transfer rate and neurologic outcomes of intracranial hemorrhage (ICH) patients.

Methods:
We performed a retrospective multicenter study comparing outcomes in patients with ICH arriving at 15 Primary Stroke Centers (PSC) and 8 CSC in Chicago, Illinois via emergency medical services transport from January 1 2017 and December 31 2023 - before and after implementation of a prehospital transport protocol in September 2018 which uses a 3-item stroke scale to identify patients with more severe stroke types and <6 hours from onset for transport to the closest CSC rather than closest PSC. Outcomes of interest included inter-hospital transfer rates, arrival to CT times, in-hospital mortality rate, favorable disposition location (discharged to home or acute rehabilitation) and favorable neurologic outcome at discharge (modified Rankin score [mRS] of 0-3).

Results:
Pre-implementation included 853 patients (mean age=63 [SD 15.0], 54% male, and 45% black), of which 232 (27%) were transported to PSCs (mean NIHSS=13 [SD 11.4]) and 621 patients (73%) to CSCs (mean NIHSS=13 [SD 9.3]). Post-implementation included 3506 patients (mean age=63 [SD 15.3], 63% male, 45% black), of which 891 (25%) went to PSCs (mean NIHSS=13 [SD 11.4]) and 2615 (75%) went to CSCs (mean NIHSS=15 [SD 10.5]). Initial NIHSS score was higher post-implementation compared to pre-implementation (13 [SD 9.9] vs. 14 [SD 10.7]), p=0.04). There were similar rates (41% pre-implementation vs 43% post-implementation) of inter-hospital transfer (p=0.39). Time from hospital arrival to CT imaging was significantly faster post-implementation (86 min vs 36 min, p<0.0001). Rates of favorable discharge disposition (49% pre-implementation vs. 47% post-implementation, p=0.28) and neurologic outcome (29% pre vs 26% post, p=0.13) were similar after adjusting for age, sex, time to CT, and initial NIHSS. However, in-hospital mortality was significantly higher post-implementation (15% pre vs. 20% post, odd ratio=1.4, 95% CI[1.1-1.8], p=0.02) after adjusting for initial NIHSS score.

Conclusion
Implementation of a regional prehospital transport protocol to stroke center was associated with a shorter time to CT scanner but higher mortality. Our findings do not support prehospital policies to transport ICH patients directly to CSCs.