A prospective multicenter biomarker study with adult patients treated on

intensive care units after out-of-hospital cardiac arrest. Patients will be recruited from specific sites participating in the Sedation, Temperature and Pressure After Cardiac Arrest and Resuscitation (STEPCARE) trial. (ClinicalTrials.gov ID NCT05564754).

Blood samples will be collected at 12, 24, 48, and 72 hours after randomization in selected sites, aliquoted and frozen on-site. After trial completion, samples will be stored in a central biobank. Sample analysis will be performed in batch after trial completion. Functional outcome will be assessed at 30 days and 6 months after cardiac arrest.

A prospective multicenter biomarker study with adult patients treated on intensive care units after out-of-hospital cardiac arrest. Patients will be recruited from specific sites participating in the Sedation, Temperature and Pressure After Cardiac Arrest and Resuscitation (STEPCARE) trial. (ClinicalTrials.gov ID NCT05564754). The STEPCARE-trial is a 2x2x2 randomised trial studying patients who have been resuscitated from cardiac arrest and who are comatose. It will include three different interventions focusing on sedation targets, temperature targets and mean arterial pressure targets.

3500 patients who are comatose after cardiac arrest will be included in the STEPCARE trial studying three separate targets. All patients will be randomised to a control or an intervention arm for sedation, temperature and blood pressure targets as follows:

• Continuous deep sedation for 36 hours or minimal sedation (SEDCARE)
• Fever management with or without a feedback-controlled device (TEMPCARE)
• A mean arterial pressure target of >85mmHg or >65mmHg. (MAPCARE)

Hospitals participating in the STEPCARE trial may opt to participate in the biomarker substudy if they include >20 patients/year, have the possibility to collect and process samples 24/7. Processing should be done by professional or experienced personnel.

Blood samples will be collected at 12, 24, 48, and 72 hours after randomization in selected sites, aliquoted and frozen on-site. Serum, plasma and PAX-RNA vials are collected. After trial completion, samples will be stored in a central biobank. Sample analysis will be performed in batch after trial completion.

Functional outcome will be assessed at 30 days and 6 months after cardiac arrest. Primary outcome is poor functional outcome (modified Rankin Scale 4-6) at six months. Secondary outcomes are poor functional outcome at 30 days and survival at 6 months.

Inclusion Criteria:

• From sites participating in the STEPCARE biomarker substudy and withOut-of-hospital cardiac arrest
• Sustained ROSC - defined as 20 minutes with signs of circulation without the need for chest compressions
• Unconsciousness defined as not being able to obey verbal commands (FOUR-score motor response of <4) or being intubated and sedated because of agitation after sustained ROSC.
• Eligible for intensive care without restrictions or limitations
• Inclusion within 4 hours of ROSC

Exclusion Criteria:

• On ECMO prior to randomization
• Pregnancy
• Suspected or confirmed intracranial hemorrhage
• Previously randomized in the STEPCARE trial.

Adult patients with an out-of-hospital cardiac arrest from sites participating in the biobank substudy of the STEPCARE trial will be included.

Upon reasonable request following publication.