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Providing a simple and consistent solution for the definition of in- versus out-of-hospital cardiac arrest

      To the Editor,
      Accurate reporting of cardiac arrest incidence is essential to inform about the burden of illness and healthcare system performance. Based on epidemiological and clinical differences, cardiac arrest is further defined as in-hospital or out-of-hospital.
      • Perkins G.D.
      • Jacobs I.G.
      • Nadkarni V.M.
      • et al.
      Cardiac arrest and cardiopulmonary resuscitation outcome reports: update and simplification of the Utstein templates for resuscitation registries.
      • Nolan J.P.
      • Berg R.A.
      • Andersen L.W.
      • et al.
      Cardiac arrest and cardiopulmonary resuscitation outcome reports: update of the Utstein resuscitation registry template for in-hospital cardiac arrest.
      This distinction by location at first seems clear but there is significant variation in definition of numerator and denominator with significant impacts on cardiac arrest incidence and survival.
      Out-of-hospital cardiac arrest (OHCA) is generally defined as resuscitation by an emergency medical service (EMS) and the denominator is the population served by the EMS
      • Perkins G.D.
      • Jacobs I.G.
      • Nadkarni V.M.
      • et al.
      Cardiac arrest and cardiopulmonary resuscitation outcome reports: update and simplification of the Utstein templates for resuscitation registries.
      (Table 1). Effective data linkage between EMS and hospital systems is needed to ensure that non-EMS attended OHCAs transported to hospital by private vehicle are included in OHCA incidence reports.
      Table 1Issues with current definition of cardiac arrest location for reporting incidence.
      NumeratorDenominatorCommon data sourceIssues
      OHCA
      • Perkins G.D.
      • Jacobs I.G.
      • Nadkarni V.M.
      • et al.
      Cardiac arrest and cardiopulmonary resuscitation outcome reports: update and simplification of the Utstein templates for resuscitation registries.
      EMS-resuscitationPopulation served by EMSEMS databaseNon-EMS attended OHCAs missed
      IHCA
      • Nolan J.P.
      • Berg R.A.
      • Andersen L.W.
      • et al.
      Cardiac arrest and cardiopulmonary resuscitation outcome reports: update of the Utstein resuscitation registry template for in-hospital cardiac arrest.
      • Cummins R.O.
      • Chamberlain D.
      • Hazinski M.F.
      • et al.
      Recommended guidelines for reviewing, reporting, and conducting research on in-hospital resuscitation: the in-hospital ‘Utstein style’.
      • Morrison L.J.
      • Neumar R.W.
      • Zimmerman J.L.
      • et al.
      Strategies for improving survival after in-hospital cardiac arrest in the United States: 2013 consensus recommendations: a consensus statement from the American heart association.
      Patients in a hospital bed +/− outpatients, employees, visitorsAdmitted patients (includes day cases)Hospital code databaseInconsistent definition

      Non-admitted patients under-reported
      OHCA, out-of-hospital cardiac arrest; IHCA, in-hospital cardiac arrest; EMS, emergency medical services.
      In-hospital cardiac arrest (IHCA) was defined by the 1997 Utstein guidelines as ‘all patients who occupy a hospital bed’.
      • Cummins R.O.
      • Chamberlain D.
      • Hazinski M.F.
      • et al.
      Recommended guidelines for reviewing, reporting, and conducting research on in-hospital resuscitation: the in-hospital ‘Utstein style’.
      The 2019 Utstein update,
      • Nolan J.P.
      • Berg R.A.
      • Andersen L.W.
      • et al.
      Cardiac arrest and cardiopulmonary resuscitation outcome reports: update of the Utstein resuscitation registry template for in-hospital cardiac arrest.
      as well as the 2013 American Heart Association (AHA) consensus,
      • Morrison L.J.
      • Neumar R.W.
      • Zimmerman J.L.
      • et al.
      Strategies for improving survival after in-hospital cardiac arrest in the United States: 2013 consensus recommendations: a consensus statement from the American heart association.
      additionally include arrests within a hospital facility in non-admitted persons such as outpatients (including emergency department (ED) arrests), employees, and visitors. However, both the 1997 Utstein guideline and 2013 AHA consensus, but not the 2019 Utstein guideline, exclude cardiac arrest in non-admitted persons from the numerator and denominator of IHCA incidence calculations because it is impossible to know the true number of non-admitted persons within a hospital facility to include in the denominator.
      The distinction between IHCA and OHCA needs to be clear and exhaustive, such that patients excluded from one classification are included in the other. We therefore propose a simple definition:IHCA: Cardiac arrest in persons who occupy an ED or inpatient hospital bedOHCA: Cardiac arrest in persons who do not occupy an ED or inpatient hospital bed
      Although arrests within a hospital facility in outpatients, employees and visitors have been previously defined as IHCA, we argue that they are better placed within the OHCA definition. The hospital setting may expedite resuscitation, similar to EMS-witnessed OHCA, but in essence an arrest in the hospital cafeteria or carpark is equivalent to an arrest outside the hospital. Conversely, admitted and ED patients are under expert medical care that aims to prevent cardiac arrest while providing immediate and timely resuscitation as required. ED arrests fit the categorisation of IHCA because they display similar clinical features to IHCA compared with OHCA, as recently demonstrated by Mikati et al.
      • Mikati N.
      • Callaway C.W.
      • Coppler P.J.
      • Elmer J.
      • Arrest P.P.
      Data-driven classification of arrest location for emergency department cardiac arrests.
      The inconsistency in the current definition and reporting of OHCA and IHCA makes benchmarking and research projects in these fields near impossible. Our definition is both a call to action and a simple solution for investigating differences in epidemiology, prevention, and treatment of IHCA and OHCA, and between registries.

      Conflicts of interest

      None.

      Acknowledgements

      None.

      References

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        Cardiac arrest and cardiopulmonary resuscitation outcome reports: update and simplification of the Utstein templates for resuscitation registries.
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        • Nolan J.P.
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        • et al.
        Cardiac arrest and cardiopulmonary resuscitation outcome reports: update of the Utstein resuscitation registry template for in-hospital cardiac arrest.
        Resuscitation. 2019; 4
        • Cummins R.O.
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        • Hazinski M.F.
        • et al.
        Recommended guidelines for reviewing, reporting, and conducting research on in-hospital resuscitation: the in-hospital ‘Utstein style’.
        Circulation. 1997; 95: 151-183
        • Morrison L.J.
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        Strategies for improving survival after in-hospital cardiac arrest in the United States: 2013 consensus recommendations: a consensus statement from the American heart association.
        Circulation. 2013; 127: 1538-1563
        • Mikati N.
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        Data-driven classification of arrest location for emergency department cardiac arrests.
        Resuscitation. 2020; 154: 26-30