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Studies on improvement of efficiency in ambulatory care Vegting, I.L.
2017
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Vegting, I. L. (2017). Studies on improvement of efficiency in ambulatory care.
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4 Exploring the performance of the National Early Warning Score (NEWS) in a European emergency department
N. Alam, I.L. Vegting, E. Houben, B. van Berkel, L. Vaughan, M.H.H. Kramer, P.W.B. Nanayakkara
Resuscitation. 2015 May;90:111-5
A b s t r a c t
Background: Several triage systems have been developed for use in the emergency department (ED), how- ever they are not designed to detect deterioration in patients. Deteriorating patients may be at risk of going undetected during their ED stay and are therefore vulnerable to develop serious adverse events (SAEs). The National Early Warning Score (NEWS) has a good ability to discriminate ward patients at risk of SAEs. The utility of NEWS had not yet been studied in an ED.
Objective: To explore the performance of the NEWS in an ED with regard to predicting adverse outcomes.
Design: A prospective observational study. Eligible patients were those presenting to the ED during the 6 week study period with an Emergency Severity Index (ESI) of 2 and 3 not triaged to the resuscitation room.
Intervention: The NEWS was documented at three time points: on arrival (T0), hour after arrival (T1) and at transfer to the general ward ICU (T2). The outcomes of interest were: hospital admission, ICU admission, length of stay and 30 day mortality.
Results: A total of 300 patients were assessed for eligibility. Complete data was able to be collected for 274 patients on arrival at the ED. NEWS was significantly correlated with patient outcomes, including 30 day mor- tality, hospital admission, and length of stay at all-time points. Conclusion: The NEWS measured at different time points was a good predictor of patient outcomes and can be of additional value in the ED to longitudi- nally monitor patients throughout their stay in the ED and in the hospital.
1. Introduction 1.1. Background
The triage of patients at the time of presentation to emergency departments (EDs) is crucial to the provision of safe patient care. Accurately triaging patients is difficult, requires experience and may be subject to inter-observer variability.1-3 Several triage systems have been developed for use in the ED, including the Emergency Severity Index (ESI) and the Manchester Triage Scale (MTS).4-6 These sys- tems provide a method of categorizing all incom- ing ED patients by level of acuity ranging from life threatening to non-urgent and dictate how quickly patients should be seen. However, while virtually all EDs employ triage systems to determine treatment priority, the evidence suggests that less attention is paid to the longitudinal monitoring of patients once they are in the department.7 There are no widely used scores specifically designed to detect deteriorating patients or to predict the chance of early intensive care unit (ICU) admission or death in ED patients. Further, small, single-site studies have demonstrated that longitudinal measurement of routine hemodynamic parameters in EDs is poor.7 These factors suggest that deteriorating patients may be at risk of going undetected during their ED stay and are therefore vulnerable to develop serious adverse events,8,9 such as unexpected car- diac arrest and unnecessary ICU admission, with a higher consumption of resources through longer lengths of hospital stay (LoS). First introduced in 1997, early warning scores (EWS) were developed in response to concerns about the failure to detect deteriorating physiological parameters in ward pa- tients.10 They are based on patient’s vital signs and linked to ‘triggers’, which mandate the escalation of monitoring or call for assistance. However, while EWS are now widely used internationally, there are a lot of different EWS scoring systems, with many being adapted for use in individual hospitals.11 The National Early Warning Score (NEWS), developed in conjunction with the Royal College of Physi- cians of London, has been more rigorously tested and performs better than any of the 33 published systems commonly in use.12 It has a good ability to discriminate ward patients at risk of cardiac ar- rest, death or unexpected intensive care unit (ICU)
admission and it is currently being promoted as a standardized system across the UK. The utility of NEWS has not yet been studied in an ED. The aim of this study was to explore the performance of NEWS with regard to predicting adverse outcomes, such as ICU admission and death, in adult patients as well as the ability of NEWS to predict the need for hospital admission in an ED population. The study also aimed to assess the feasibility of the use of NEWS as a structural monitoring tool in a Dutch ED.
2. Methods
2.1. Design and setting
A prospective, observational feasibility study was performed at the ED of the VU Medical Centre (VUmc), an academic urban tertiary care centre in Amsterdam, with approximately 31000 ED visits per year. The ED of the VUmc uses the Emergency Severity Index (ESI) for triage.5
2.2. Study population
Eligible patients were those of 18 years and older presenting to the ED of the VUmc during the 6 week study period (7th January till 15th February 2013, between 12.00 and 20.00 hrs) with an ESI of 2 and 3 not triaged to the resuscitation room.
Excluded were patients with an ESI 4 or 5 and patients undergoing cardiopulmonary resuscitation (ESI 1). Patients lost to follow-up were removed from the study analysis. The standard distribution of patients according to ESI at our ED is as follows:
ESI-1 4.9%, ESI-2 5.0%, ESI-3 44%, ESI-4 39.3%, ESI-5 6.7%.13 The eligibility criteria were chosen on basis of results of an earlier study performed in our ED.13 The researchers monitored patients during the time frame of 12.00–20.00 hrs as it mostly is the busiest time of the day at the ED. Patients triaged with category ESI 4 or 5 present with minor com- plaints, the larger percentage (95–99%) of these patients were discharged home within 4 hrs. The Medical Ethical Committee of the hospital approved the study. Informed consent was waived as routine care was not influenced and no therapeutic inter- vention was introduced.
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3. Results
3.1. Patient population
A total of 300 patients were assessed for eligibility.
Complete data was collected for 274 patients at moment of entry to the ED. The demographic char- acteristics are shown in table 2. NEWS measured at moment of entry for these 274 patients is shown in table 3. The NEWS was calculated an hour later in 247 patients (Table 3a). Only 133 of the 247 pa- tients could be followed up to calculate the NEWS at discharge from the ED (admitted to the ward or discharged home), as shown in table 3b. It was not possible to collect data for all patients at all-time points due to organizational reasons.
3.2. NEWS scores
At T0 NEW scores ranged from 0 to 11 with a median score of 2.0 (IQR 1–4). The distribution of NEWS measured at T0 is shown in table 3.
The distribution of NEWS measured at different time points is shown in table 3a and table 3b.
3.3. Admission
A total of 130 patients were admitted to hospital, 142 were discharged and 2 transferred to other hospitals (Table 2). Admission was significantly correlated with NEWS at T0, T1 and T2, tested with chi square (linear by linear association) with categorized NEWS (p < 0.001), see table 3a and b.
The AUROCs (95% CI) for NEWS for admission at T0, T1, T2 was respectively 0.664 (0.599–0.728), 0.687 (0.620–0.754), 0.697 (0.609–0.786).
3.4. Length of stay
Length of stay was significantly correlated with NEWS, at all of the measured time points, p value for x2 was <0.001. Spearman Rank Correlation was significant (p < 0.0001). Median length of stay more than doubled for a score >7 compared with a score of 0–4. Table 4 demonstrates the NEWS measured at T0 related to length of stay.
3.5. ICU admission
A total of 10 patients were admitted to the ICU.
We found that ICU admission significantly corre- lated with NEWS at time points T0 (Fisher’s exact test with NEWS above or below 7: p = 0.003), T1 (p < 0.001) and at T2 (p = 0.046). Five of the patients which were admitted to the ICU had an aggregate score of 0–4 while, the other five patients had aggregate scores of seven or more.
In the group of patients with low aggregate scores, there were four patients which were ad- mitted for a short while for observation and dis- charged shortly after (Table 5). The details of the patients admitted to ICU are given in table 5a.
2.3. Methodology
The data used for calculation of the NEWS were collected at three time points, namely at arrival ED (time point 0: NEWS – T0),1 hour after arrival at the ED (time point 1: NEWS – T1), and if appli- cable at transfer to a hospital ward (time point 2:
NEWS – T2). Two trained researchers (EH and BvB) collected data, which contained demographic details, medication use, medical history, and vital parameters needed to calculate the NEWS (see Table 1). This data collection was in addition to any observations taken at the time of triage. EWS scores were calculated using the NEWS-score as proposed in the report by the Royal College of Physicians.14 The outcomes of interest for this study were: hospital admission, ICU admission, length of stay and 30 day mortality.
2.4. Statistical analysis
For data analysis IBM SPSS 20.0 (Chicago, USA) was used. Student’s t test was used for inde- pendent samples to compare means for nor- mally distributed variables and Mann–Whitney U test for variables that were not normally distrib- uted. A p < 0.05 regarded as statistically signifi- cant. Descriptive statistics were used to determine patient characteristics (presented as mean ± SD).
Skewed variables were summarized using me- dian and interquartile range (IQR). Receiver Op- erating Characteristic (ROC) analysis was used to identify the NEW score for the highest sensitivity.
The NEW scores were divided into three aggre- gates, aggregate 0-4 (low clinical risk), aggregate 5-6 (medium clinical risk) and aggregate 7 or more (high clinical risk) for the purposes of this study and according to the NEWS thresholds and triggers.14
3.6. Mortality
The 30 day mortality for all patients included in the study was 4.0% (n = 11). The ESI score for 10 deceased patients was 3 and one had a score of 2. We found that mortality was significantly corre-
The 30 day mortality was not significantly relat- ed to ESI, p = 0.816. The AUROCs (95% CI) for NEWS for mortality at pT0, T1 and T2 was respec- tively 0.768 (0.618–0.919), 0.867 (0.769–0.964), 0.767 (0.568–0.966). Patients who died were older (mean age 74, 25 years; SD 11.9; independent sample t test p = 0.002) and had a higher NEWS score (mean 6.00; SD 3.6; Mann–Whitney U test p = 0.002) compared with patients who survived (mean age 59.08; SD 20.1); NEWS (mean 2.51;
SD 2.56). The mean length of stay was 8.2 days for patients who died and 4.1 days (Mann–Whitney U test p = 0.001) for patients who survived. The de- tails of the patients who died are given in table 6a.
Of the individual physiological measures compris- ing the NEW score, only the respiratory rate was significantly associated with mortality at all meas- ured time points (Table 7). Pulse rate had a strong correlation with mortality if measured an hour after entry ED (at T1). No correlations could be found for all other physiological parameters.
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4. Discussion
To the best of our knowledge this is the first pro- spective study performed in an ED to evaluate the performance of the NEWS, a standardized score.
We found that the NEWS was significantly corre- lated with patient outcomes, including 30day mor- tality, hospital admission, and length of stay at all timepoints. ICU admission was significantly corre- lated with NEWS at T0 and T1. Several studies have been performed to investigate the value of early warning scores in identifying patients at risk of de- terioration15,16, their effect on clinical outcomes17–22, and their ability to predict clinical outcomes.23–27 Using early warning score may influence clinical outcomes positively. However studies performed
Moreover, no studies have been performed to vali- date the use of NEWS in de the ED. Our study indicates a number of potential uses for the NEWS in the ED. ED triage systems such as ESI and MTS were explicitly developed to assess the priority of patients fo clinical intervention. Although some studies have demonstrated that MTS and ESI may provide us with some useful prognostic information as a predictor of admission or 24 hour mortal- ity,30–32 the validity of these triage scales has not been evaluated across different triage levels for outcomes such as early death and hospital admis- sion. Moreover there was wide variation between different triage scales as well as studies using the same scales. While physiological scoring alone is unable to identify patients at risk of poor outcomes, the recognition of which was a spur for the devel- opment of MTS in particular. Our study demon- strates that NEWS can further risk stratify patients within higher ESI risk categories, both for death and need for admission to ICU. Patients with a high NEW score have not only been identified as being at risk of a poor outcome, but have already physiologically deteriorated to the extent where ur-
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However, it is the sign which is documented most poorly in ED patients, implying that more work need to be done in the ED to improve longitudinal moni- toring of the patients during their stay at the ED.7 Our study has several limitations, as it was a single center study of observational nature in a specific setting with a convenient patient selection. Patient observations were collected by trained clinicians under trial conditions, rather than nursing staff un- der departmental pressures and so might be more accurate than routine observations. However, we could not obtain complete datasets at all consecu- tive time points; a large percentage of the patients needed diagnostic tests and were not present at the ED for further monitoring at time point T1, or were otherwise directly transported from the ED to the ward (T2). Although the researchers had request- ed to be notified when patients were discharged, nurses or other staff sometimes forgot to notify on time. Some eligible patients were also missed as only two researchers were available to calculate the NEWS during the inclusion period and only one patient at a time could be monitored. However, most of the patients who presented at the ED were included in the study at T0. Therefore this sample is a good representation of the total population of ESI 2 and 3 patients at our ED. The median age of our study population was 60 years and the mortality was relatively low (4%). The number of deceased patients was too small to perform a further in depth analysis. The dataset was also too small to detect the effect of changes on patient outcomes with each one point increase or decrease in the NEWS.
The patients in our ED stay for a relatively short period, with most patients (84%) being discharged within four hours.13 The other additional benefits of NEWS, such as improving continuity of patient care and fostering a uniform approach to the unwell patient, were unable to be explored. The stand- ardization of the score however offers many op- portunities of easier implementation, e.g. incorpo- ration of NEWS education in the nursing curriculum.
Again, within higher triage categories, NEWS dem- onstrated that it was able to predict not only the need for admission, but length of inpatient stay. This suggests that not only patients with higher NEW scores should be seen more urgently by medi- cal staff, but these patients could be fast tracked for admission once stabilized. This study stands in contrast to others on the performance of NEWS, as mortality was calculated at 30 days, rather than within 24 hrs. This was a pragmatic choice, due to the small sample size and, as predicted, no patients in the study died or experienced an unex- pected cardiac arrest within 24 hrs of presentation.
NEWS was a reasonable predictor of death at 30 days and all patients who died during the course of the index admission has NEWS scores that classi- fied them as being at medium or high clinical risk.
The four patients who were identified as being low risk who died within 30 days all did so either within a palliative setting on the index admission or on a subsequent admission. The study also looked at patients longitudinally, rather than at single time points. Therefore NEWS seems to be a good pre- dictor of mortality at 30 days, even when calculated at different time points during the stay at the ED.
This study conceived, in part, to explore the utility of NEWS as a structural monitoring system in the ED, analogous to its ward use. The study demon- strated that using NEWS was possible in the ED setting, although much larger studies are needed to determine how frequently observations need to be performed and whether the trigger thresholds for intervention need to be adjusted in ED patients.
These findings suggest that the use of NEWS in conjunction with the ESI triage has the potential to better identify patients in need of urgent attention and potentially expedite admissions to the medi- cal wards and intensive care, thereby smoothing patient flow through the ED. Our study differs from previous work as we measured the NEWS at dif- ferent time points during a patients stay at the ED.
Furthermore, motivated and trained researchers performed the measurements. For a proper uptake and implementation of the NEWS in future, train- ing and motivating the staff is important. Quality of care may be greatly improved by a more col- laborative approach, where in the NEWS can be a potential asset. A standardized approach, such as the NEWS, can help in improving continuity of care, improve communication between staff and provide a basis for the management of critically ill patients. When comparing the individual physi- ological parameters of the deceased patients with the patients who survived, respiratory rate had the most significant correlation with mortality in our
5. Conclusion
The NEWS measured at different time points was a good predictor of patient outcomes. The NEWS can be of additional value in the ED, although not specifically as a triage system, but as a means to longitudinally monitor patients throughout their stay in the ED and in the hospital. Through its use, clini- cal staff has a better indication whether a patient is more at risk. Hereby making it possible to timely intervene and stabilize a patient before further dete-
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