PRE-hospital Cooling to improvE carDiac arrEst Neurological outComEs (PRECEDENCE)

Background: Despite advances in resuscitation, neurological recovery after out-of-hospital cardiac arrest (OHCA) remains poor. Current hospital-initiated targeted temperature management (TTM) often begins several hours after ROSC, potentially missing the optimal neuroprotective window. Early or ultra-early cooling during the pre-hospital phase may mitigate ischemia-reperfusion brain injury, but evidence from real-world EMS settings is limited. Rationale: The PRECEDENCE study tests the operational feasibility of initiating TTM in the pre-hospital environment using a novel, power-free CarbonCool® cooling vest designed for rapid application by paramedics immediately after ROSC. The vest provides conductive surface cooling without interfering with resuscitation, transport, or diagnostics. Study Design: PRECEDENCE is a pilot feasibility trial conducted by the Singapore Civil Defence Force (SCDF) and collaborating hospital. Eligible OHCA patients attended by SCDF Division 4 paramedics will be allocated to either (a) pre-hospital TTM using the CarbonCool® vest or (b) standard pre-hospital care, depending on predefined eligibility and operational criteria. Both groups will be prospectively followed through hospital discharge. Outcomes: The primary outcome is feasibility of implementing pre-hospital TTM, evaluated through recruitment rates, intervention delivery, protocol fidelity, and provider acceptability. Secondary outcomes include hospital TTM uptake, time from ROSC to target temperature, neurological outcome at discharge (CPC 1-2), and predefined safety endpoints (overshoot cooling \< 33 °C, hemodynamically significant bradyarrhythmias, and skin injury). Significance: By assessing real-world feasibility and safety of early pre-hospital cooling, this pilot will provide critical implementation data and guide protocol refinements for a future multi-division or national randomized trial.