This is an investigator-initiated, multicenter, randomized, placebo-controlled, parallel group, double-blind, superiority trial of calcium during adult out-of-hospital cardiac arrest. 430 adult patients with out-of-hospital cardiac arrest receiving at least one dose of adrenaline will be enrolled. The primary outcome is sustained return of spontaneous circulation and key secondary outcomes include survival at 30 days and survival at 30 days with a favorable neurological outcome.

Inclusion Criteria:

• Out-of-hospital cardiac arrest
• Age ≥ 18 years
• Received at least one dose of adrenaline

Exclusion Criteria:

• Traumatic cardiac arrest - including drowning and external asphyxia (e.g., hanging, strangulation, or foreign object airway obstruction)
• Known or strongly suspected pregnancy
• Prior enrollment in the trial
• Received adrenaline during cardiac arrest before arrival of prehospital personnel with the study drug
• Clinical indication for calcium administration during the cardiac arrest

Six months after the publication of the last results, all deidentified individual patient data will be made available for data sharing. Procedures, including re-coding of key variables, will be put in place to allow for complete deidentification of the data. Data will be completely anonymized according to Danish law.

Six months after the publication of the last results

Data will be available for any research purpose to all interested parties who have approval from an independent review committee and who have a methodological sound proposal as determined by the steering committee of the current trial. Only the methodological qualities and not the purpose or objective of the proposal will be considered.

All patients received the trial drug and meeting all inclusion criteria and none of the exclusion criteria.

30 days

Adverse events were not collected.