Pre-hospital treatment duration and efficacy of remote ischaemic conditioning in the RESIST randomised-controlled...

Remote ischaemic conditioning (RIC) initiated pre-hospital did not improve 90-day functional outcomes after acute stroke in the RESIST trial. The duration of treatment pre-reperfusion modifies treatment effect for other neuroprotective therapies. We examined whether the effects of RIC might be modified by the duration of pre-hospital treatment.

This post-hoc analysis of the RESIST randomised-controlled trial (ClinicalTrials.gov: NCT03481777) included patients who presented with pre-hospital stroke symptoms < 4 hours, randomised to RIC or sham, diagnosed with acute ischaemic stroke (AIS) or ICH (modified intention-to-treat [mITT] cohort). Patients were stratified by time from randomisation to hospital admission (ie, pre-hospital treatment duration). The primary outcome was shift in 90-day mRS; secondary outcomes were 90-day mRS 0-2 and 24-hour neurological improvement (NIHSS).

Among 902 mITT patients (AIS, n = 737; ICH, n = 165), median randomisation-to-admission time was 29.4 minutes (IQR: 19.6-39.4) and median onset-to-admission time was 88 minutes (IQR: 62.4-131.3). Across pre-hospital treatment duration strata, RIC conferred no significant benefit on 90-day mRS, mRS 0-2 or early NIHSS improvement in the combined, AIS or ICH populations. In patients with AIS receiving reperfusion therapy, stratification by transport time likewise revealed no efficacy differences. No significant interaction was observed between RIC and pre-hospital treatment duration for any outcome.

Longer pre-hospital treatment duration was not associated with efficacy of RIC in the RESIST trial including in patients with AIS who received reperfusion therapies. Findings may not apply to settings where RIC could be routinely administered for longer periods. We found no treatment duration-dependent benefit of pre-hospital RIC, at least when durations are under an hour.