Elsevier

Resuscitation

Volume 85, Issue 5, May 2014, Pages 587-594
Resuscitation

Review article
The impact of the use of the Early Warning Score (EWS) on patient outcomes: A systematic review

https://doi.org/10.1016/j.resuscitation.2014.01.013Get rights and content

Abstract

Background

Acute deterioration in critical ill patients is often preceded by changes in physiological parameters, such as pulse, blood pressure, temperature and respiratory rate. If these changes in the patient's vital parameters are recognized early, excess mortality and serious adverse events (SAEs) such as cardiac arrest may be prevented. The Early Warning Score (EWS) is a scoring system which assists with the detection of physiological changes and may help identify patients at risk of further deterioration.

Objectives

The aim of this systematic review is to evaluate the impact of the use of the Early Warning Score (EWS) on particular patient outcomes, such as in-hospital mortality, patterns of intensive care unit admission and usage, length of hospital stay, cardiac arrests and other serious adverse events of adult patients on general wards and in medical admission units.

Design and setting

Systematic review of studies identified from the bibliographic databases of PubMed, EMBASE.com and The Cochrane Library.

Selection criteria

All controlled studies which measured in-hospital mortality, ICU mortality, serious adverse events (SAEs), cardiopulmonary arrest, length of stay and documentation of physiological parameters which used a EWS on the ward or the emergency department to identify patients at risk were included in the review.

Data collection and analysis

Three reviewers (NA, AT and EH) independently screened all potentially relevant titles and abstracts for eligibility, by using a standardized data-worksheet. Meta-analysis was not possible due to heterogeneity.

Main results

Seven studies met the inclusion criteria. The results of our included studies were mixed, with a positive trend towards better clinical outcomes following the introduction of the EWS chart, sometimes coupled with an outreach service.

Six of the seven included studies used mortality as an endpoint: two of these studies reported no significant difference in in-hospital mortality rate; two found a significant reduction of in-hospital mortality; two other studies described a trend towards improved survival. Although, both ICU mortality and serious adverse events were not significantly improved, there was a trend towards reduction of these endpoints after introduction of the EWS. However only two studies looked respectively at each endpoint.

There were conflicting results concerning cardiopulmonary arrests. One study found a reduction in the incidence of cardiac arrest calls as well as in the mortality of patients who underwent CPR, while another one found an increased incidence of cardio-pulmonary arrests. Neither study met all methodological quality criteria.

Conclusion

The EWS itself is a simple and easy to use tool at the bedside, which may be of help in recognizing patients with potential for acute deterioration. Coupled with an outreach service, it may be used to timely initiate adequate treatment upon recognition, which may influence the clinical outcomes positively. However, the use of adapted forms of the EWS together with different thresholds, poor or inadequate methodology makes it difficult in drawing comparisons. A general conclusion can thus not be generated from the lack of use of a single standardized score and the use of different populations. In future large multi-centre trials using one standardized score are needed also in order to facilitate comparison.

Introduction

Acute deterioration in patients is often preceded by subtle changes in physiological parameters such as pulse, blood pressure, respiratory rate and level of consciousness.1, 2, 3, 4 Both prospective and retrospective chart reviews as well as a recent report published by the NCEPOD show that evidence of clinical deterioration is often present for hours prior to the occurrence of serious adverse events (SAEs) such as cardiac arrest, death and intensive care unit admission, leading to the conclusion that many of these SAEs might be preventable.3, 5, 6, 7, 8 Factors involved in ‘preventable’ SAEs frequently include poor clinical monitoring, inadequate interpretation of changes in physiological parameters and failure to undertake appropriate action.9, 10, 11, 12 Further, the inability to accurately recognize and initiate treatment of the critically unwell patient not only leads to higher levels of morbidity, but excessive utilization of costly resources, such as increased ICU usage and longer inpatient stay, a pressing issue in a climate of intense financial constraint.

Hospitals need tools to help them recognize patients at risk of deterioration in order to give the right care at the right moment before any SAEs arise The concept of the Early Warning Score (EWS), was developed in 1997 by Morgan et al.13 It consists of a simple to use algorithm based on physiological parameters, such as heart rate, systolic blood pressure, respiratory rate, temperature and mental state. As this simple scoring tool can easily be utilized during the routine bedside observations, it is considered helpful in recognizing patients exhibiting signs of acute deterioration, but also obtaining timely assistance of a skilled clinician. The EWS is mostly coupled with a team (e.g. Critical Care Outreach Service (CCOS), Rapid Response Team (RRT), Patient at Risk Teams (PART)), consisting of experienced medical and/or nursing staff who can provide the support to timely manage the deteriorating patient 32 and thus help improving patient outcomes.

Section snippets

Objectives

In the last decade, several reviews have been carried out concerning critical outreach services using various scoring systems.14, 15, 16, 17, 18 However, most of the studies reviewed the use of a CCOS or an RRT as an efferent limb together with different kinds of early warning systems (afferent limb) rather than the utility of the Early Warning Score and its derived forms.19 Many studies have investigated some form of an EWS system with (or without) a coupled outreach service, finding positive

Search strategy

To identify all relevant publications, we performed systematic searches in the bibliographic databases PubMed, EMBASE.com and The Cochrane Library (via Wiley) from inception to April 8, 2013. Search terms included controlled terms from MeSH in PubMed, EMtree in EMBASE.com as well as free text terms. We used free text terms only in The Cochrane library. Search terms expressing ‘Early Warning Score’ were used in combination with search terms comprising ‘hospital’ and terms for ‘hospital setting’

Mortality

Of the seven included studies,7, 8, 10, 22, 23, 24 six evaluated mortality. Two studies7, 8 found that introduction of an EWS chart after an intensive staff education programme resulted in a significant reduction in overall mortality. Paterson et al.7 found a reduction of in-hospital mortality of 2.8% (p = 0.046), from 5.8% before implementation of EWS to 3.0% after implementation. Moon et al.8 found that the in-hospital mortality significantly reduced from 1.4% to 1.2% (p < 0.0001).

Three studies22

Discussion

In this systematic review we identified seven studies which met our inclusion criteria. These seven studies were all studies investigating patient outcomes before and after implementation of an Early Warning Scores, sometimes coupled with a CCOS. As all included studies were highly heterogeneous in study population, sample sizes and the use of different forms of Early Warning Scores with different alarm thresholds with or without a coupled CCOS, a meta-analysis for different patient subgroups

Conclusion

Despite the fact that much effort has been put in the last decade in developing early warning scoring systems for recognizing patients at risk for deterioration, there still remains a need for improvement in recognition and response. The results of our included studies were mixed, but in general there was a positive trend towards clinical outcomes after the introduction of an EWS system. As the other available scoring systems are either too complex to use or only validated for specific patient

Conflict of interest statement

All authors have disclosed that they do not have any potential conflict of interest.

Acknowledgement

The authors are grateful for the invaluable help of Dr. Louella Vaughan, NWL CLAHRC and Chelsea & Westminster Hospital, Senior Clinical Research Lead and Honorary Consultant Physician, in reviewing our manuscript.

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    A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.01.013.

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