The study will have an observational retrospective cross-sectional design. Patient records and hospital administrative systems at 10 hospitals in Sweden will be searched using ICD-codes to find all patients treated for an in-hospital cardiac arrest (IHCA) during the time period of 20180101 to 20191231. All found patients will be cross-checked against reported patients in the Swedish Registry of Cardiopulmonary Resuscitation (SRCR). Any differences in patient characteristics or regarding situation factors between reported and non-reported patients will be evaluated. Non-reported patients will be retrospectively reported to the registry. An incidence of IHCA will be calculated using the number of patients treated for IHCA divided by number of hospital admissions during the specific time period. Selected variables will be evaluated regarding compliance to report and regarding concordance with patient records. All missing data will be described and evaluated. Local reporting procedures at each hospital will be described and evaluated regarding compliance to report and regarding missing data.

Inclusion Criteria:

• All patients after the neonatal period that have been treated for an in-hospital cardiac arrest.

Exclusion Criteria:

• Patients with an in-hospital cardiac arrest that is not treated (do not attempt resuscitation) or patients in the neonatal period.

An in-hospital cardiac arrest is defined as an arrest that occurs in a hospitalized patient who had a pulse at the time of admission. A hospital is defined as a facility with twenty-four hours a day care including an intensive care unit and an emergency team. Treatment of a cardiac arrest involves initiation of CPR or defibrillation. Data of patients treated for in-hospital cardiac arrest will be collected from 10 hospitals of varying size during 20180101 to 20191231 in Sweden. Data of reported patients treated for in-hospital cardiac arrest during the same time period at each hospital will be extracted from the SRCR .