Incidence and case ascertainment of treated in-hospital cardiac arrest events in a national quality registry - A comparison of reported and non-reported events

Background: Approximately 2500 in -hospital cardiac arrest (IHCA) events are reported annually to the Swedish Registry of Cardiopulmonary Resuscitation (SRCR) with an estimated incidence of 1.7/1000 hospital admissions. The aim of this study was to evaluate the compliance in reporting IHCA events to the SRCR and to compare reported IHCA events with possible non -reported events, and to estimate IHCA incidence. Methods: Fifteen diagnose codes, eight Classification of Care Measure codes, and two perioperative complication codes were used to find all treated IHCAs in 2018-2019 at six hospitals of varying sizes and resources. All identified IHCA events were cross-checked against the SRCR using personal identity numbers. All non -reported IHCA events were retrospectively reported and compared with the prospectively reported events. Results: A total of 3638 hospital medical records were reviewed and 1109 IHCA events in 999 patients were identified, with 254 of the events not found in the SRCR. The case completeness was 77% (range 55-94%). IHCA incidence was 2.9/1000 hospital admissions and 12.4/1000 admissions to intensive care units. The retrospectively reported events were more often found on monitored wards, involved patients who were younger, had less comorbidity, were often found in shockable rhythm and more often achieved sustained spontaneous circulation, compared with in prospectively reported events. Conclusion: IHCA case completeness in the SRCR was 77% and IHCA incidence was 2.9/1000 hospital admissions. The retrospectively reported IHCA events were found in monitored areas where the rapid response team was not alerted, which might have affected regular reporting procedures.