Prehospital recruitment of ultra-early ICH patients in the STOP-MSU trial: implications for patient selection in ICH trials.

Abstract

Background/Aims: The STOP-MSU RCT of tranexamic acid (TXA) in ICH <2h onset was the first haemostatic trial to include recruitment on a Mobile Stroke Unit (MSU). Although the trial did not demonstrate benefit of TXA, we investigated haematoma growth and outcomes in participants receiving prehospital treatment on the MSU compared to hospital-recruited patients. Method(s): We conducted a post-hoc analysis of the STOP-MSU trial assuming neutral treatment effect. We compared MSU-recruited to hospital-recruited patients for treatment time and haematoma growth (dichotomised 33%/6ml or absolute growth) and 90-day mRS (adjusted for age, sex, NIHSS and baseline ICH volume). Result(s): Of n=201 trial patients, 44(21.9%) were recruited on MSU. There were no significant differences in baseline demographics including age, location, baseline volume, BP or glucose. MSU-recruited patients received faster treatment from onset (76min [IQR 67.5-100] vs 107min [IQR 97-118], p<0.001) and were treated more frequently <=60min (OR 15.0[95%CI 3.0-75.1]). MSU patients had higher rates of growth on both dichotomised (52.3% vs 36.3%, aOR 2.0[95%CI 1.0-4.2], p=0.062) and absolute criteria (median 3.3ml [IQR 0.5-17.8] vs 0.8ml [IQR -0.8-6.5], mean 16.0ml [SD28.5] vs 7.0 [SD15.4]). MSU patients trended towards poorer outcomes for mRS 0-3/return-to-baseline (40.9% vs 52.2%, aOR 0.75 [95%CI 0.33-1.71]) and mortality (25.0% vs 14.7%, aOR 1.3 [95%CI 0.4-3.8] with no modification from TXA (pinteraction= 0.07). Conclusion(s): MSU-recruited patients received significantly faster treatment and showed a two-fold increased odds of haematoma growth compared to hospital-recruited patients. Growth parameters were comparable or even surpassed previous TXA trials that required CTA spot-sign for eligibility. As such MSU-facilitated ultra-early recruitment may be key for optimal patient selection in acute ICH trials.