Design and rationale of the SPARC trial: a phase II, single-system randomized controlled trial of immediate transfer to specialty post-arrest care

Background: Out-of-hospital cardiac arrest (OHCA) is common and often fatal. Survivors who reach the hospital require complex, time-sensitive care, but outcomes vary widely across hospitals. Observational data suggest regionalized specialty post-arrest care may improve outcomes, yet the causal effect of an early transfer strategy is uncertain and must be balanced against the risks of interfacility transfer. Methods: SPARC ("The effect of SPecialty cAre on Recovery from Cardiac arrest") is a phase II, parallel-group randomized controlled trial in a single US health system. We will enroll 1618 adults resuscitated from OHCA who survive to emergency department (ED) care. Under Exception from Informed Consent (21 CFR 50.24), participants will be randomly assigned 1:1 to (1) immediate ED-to-ED transfer to a post-cardiac arrest specialty (PCAS) center or (2) usual care at the presenting hospital. The primary outcome is 90-day modified Rankin Scale (mRS) assessed by a trained, blinded outcome assessor. The primary analysis will be intention-to-treat using a covariate-adjusted Bayesian partial proportional odds model. Interim analyses for superiority/futility will occur at 50% and 75%, with a prespecified adaptive sample-size re-estimation at the first interim analysis. Discussion: SPARC directly tests whether an early transfer strategy to a mature PCAS center improves functional outcomes compared with usual care in a mixed urban, suburban, and rural region. Results will inform the design of post-arrest systems of care and the feasibility of a definitive multicenter trial. Trial registration: ClinicalTrials.gov NCT07002294. Protocol version: 1.22 (Version date February 24, 2026; IRB approved February 25, 2026; DSMB approved February 25, 2026).