The PRE-hospital Cooling to improvE carDiac arrEst Neurological outComEs (PRECEDENCE) study is a pilot feasibility trial evaluating the implementation of pre-hospital targeted temperature management (TTM) using a wearable surface cooling device (CarbonCool® vest) in adult out-of-hospital cardiac arrest (OHCA) patients with return of spontaneous circulation (ROSC). The study aims to assess feasibility, fidelity, acceptability, and safety of initiating cooling in the field by emergency medical services (EMS) prior to hospital arrival. Results will inform the design of a larger definitive trial to determine the clinical effectiveness of early pre-hospital TTM in improving neurological outcomes.

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.

Inclusion Criteria:

1. Out-of-hospital cardiac arrest (OHCA) of any rhythm attended by Singapore Civil Defence Force (SCDF) paramedics.
2. Return of spontaneous circulation (ROSC) achieved in the pre-hospital setting.
3. Age ≥16 years and ≤80 years.
4. Patient remains comatose after ROSC, with Glasgow Coma Scale (GCS) ≤8.

Exclusion Criteria:

1. Age >80 years.
2. Traumatic cause of cardiac arrest.
3. Tympanic temperature <34°C at time of assessment.
4. Pregnant females.
5. Termination of resuscitation in the Emergency Department.
6. Withdrawal of life support within 24 hours of Coronary Care Unit (CCU) admission.

This is an open-label study. Masking of participants, care providers, and outcome assessors is not feasible due to the visible and operational nature of the cooling intervention in the pre-hospital environment. All analyses will be performed by the research team using de-identified data to minimize potential assessment bias.