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Comparison of an early warning score to single-triggering warning system for inpatient deterioration: An audit of 4089 medical emergency calls

  • Ahmed Khalaf
    Affiliations
    Medical School, Australian National University, Florey Building 54 Mills Road, Acton, ACT 2601, Australia
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  • Zsuzsoka Kecskes
    Affiliations
    Medical School, Australian National University, Florey Building 54 Mills Road, Acton, ACT 2601, Australia

    Department of Neonatology, Canberra Hospital, Yamba Dr, Garran, ACT 2605, Australia
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  • Ekavi N. Georgousopoulou
    Affiliations
    Medical School, Australian National University, Florey Building 54 Mills Road, Acton, ACT 2601, Australia

    Centre for Advances in Epidemiology & IT, Canberra Hospital, Yamba Dr, Garran, ACT 2605, Australia
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  • Imogen A. Mitchell
    Correspondence
    Corresponding author at: Australian National University, Florey Building, 54 Mills Road, Acton, ACT, 2601 Canberra, Australia.
    Affiliations
    Medical School, Australian National University, Florey Building 54 Mills Road, Acton, ACT 2601 Australia

    Intensive Care Unit, Canberra Hospital, Yamba Dr, Garran, ACT 2605, Australia
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      Abbreviations:

      ACT (Australian Capital Territory), NSW (New South Wales), MET (Medical Emergency Team), ICU (Intensive Care Unit), MEWS (Modified Early Warning Score), BTF (Between The Flags system), RR (respiratory rate), HR (heart rate), sBP (systolic blood pressure), SaO2 (arterial oxygen saturation), T (temperature)
      Dear Editor,
      Various studies have compared different track and trigger systems for their ability to identify patients at risk of deterioration,
      • Green M.
      • Lander H.
      • Snyder A.
      • Hudson P.
      • Churpek M.
      • Edelson D.
      Comparison of the Between the Flags calling criteria to the MEWS, NEWS and the electronic Cardiac Arrest Risk Triage (eCART) score for the identification of deteriorating ward patients.
      however, an optimal system is yet to emerge.
      • Gao H.
      • McDonnell A.
      • Harrison D.A.
      • Moore T.
      • Adam S.
      • Daly K.
      • et al.
      Systematic review and evaluation of physiological track and trigger warning systems for identifying at-risk patients on the ward.
      The aim of this study was to compare a multi-parameter track and trigger system (Modified Early Warning Score [MEWS]), used in the Australian Capital Territory (ACT),
      • Mitchell I.A.
      • Kulh M.A.
      • McKay H.
      Use of the modified early warning score in emergency medical units.
      with a single-parameter track and trigger system (“Between the Flags” [BTF]) used in New South Wales (NSW)
      • Hughes C.
      • Pain C.
      • Braithwaite J.
      • Hillman K.
      ‘Between the flags’: implementing a rapid response system at scale.
      and assess their timeliness in detecting patient deterioration 24 hours prior to a Medical Emergency Team (MET) activation. Although the systems differ in their analysis of a patient’s physiological state, the parameters tracked are the same (temperature (T), respiratory rate (RR), heart rate (HR), arterial oxygen saturation (SaO2), systolic blood pressure (SBP), and sedation/consciousness level). Assessing timeliness involved looking at each system’s ability to trigger a ward review prior to activating the MET.
      A retrospective observational study (ETHLR.15.168; Date: 08/09/2015) was conducted at the Canberra Hospital (TCH), ACT, Australia. All adults who underwent a MET activation at TCH between 1st January 2008 and 30th June 2015 were considered for participation, excluding patients with data recorded for less than 24 hours (e.g. new admissions, emergency department, visitors). Both MEWS and BTF we retrospectively applied to the patients’ observations.
      In total, 4,615 MET records were retrieved and after applying the exclusion criteria, the study dataset consisted of 4,089 MET activations matched to 3,159 patients. Patients were predominantly male (54%, 1,719/3,159), with a median age of 71 years (1st, 3rd quartile: (57,81)) and high hospital mortality (29.6%, 935/3,159). Means of physiological parameters 0–2 hours prior to MET activation were significantly different to those taken at 2–4 and 4–6 hours prior to the MET activation; for RR (20.9 vs 19.7 and 19.4 breaths/min respectively, p < 0.001), HR (93.8 vs 89.8 and 88.5 beats/min respectively, p < 0.001) and SaO2 (94.7 vs 95.5 and 95.7 respectively, p < 0.001). When applying the BTF system to the data, the estimated median time from ward medical review to MET activation was 16.50 hours (1st, 3rd quartile: 9.0, 21.8, Fig. 1), which was significantly earlier than the ACT system (16.5 vs. 7.49 hours, p < 0.01).
      Fig. 1
      Fig. 1Physiological deterioration, 24 hours before MET activation for a) RR, b) HR, c) sBP, d) SaO2, and e) T. Significant differences within the final 12 hours are shown for respective groups.
      According to our data, physiological deterioration occurred most markedly in the 4 hours prior to MET activation and BTF would have activated a ward review significantly earlier than MEWS. This observation is very important, as previous research shows that within the first 30 hours from admission, derangements in physiological observations were highly correlated with mortality rates
      • Kellett J.
      • Woodworth S.
      • Wang F.
      • Huang W.
      Changes and their prognostic implications in the abbreviated Vitalpac™ early warning score (ViEWS) after admission to hospital of 18,853 acutely ill medical patients.
      and thus, timely recognition should lead to timely intervention and reduction of adverse events rates. The study included a large number of patients and vital sign measurements, however, is limited to patients in a single centre and thus, the NSW system application to the data is retrospective and hypothetical.
      In conclusion, the BTF single-variable track and trigger system identified patient deterioration earlier than the ACT multivariable system MEWS. Further research is needed to determine if earlier identification of patient deterioration improves the outcomes of deteriorating patients.

      Conflicts of Interest

      None to declare.

      Acknowledgements

      Thank you to Associate Professor Bruce Shadbolt and Mr Tim Brown (Centre for Advances in Epidemiology & IT, Canberra Hospital) for their advice.

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