Utility of a Single Early Warning Score for Sepsis in the ED
Utility of a Single Early Warning Score for Sepsis in the ED
Systems for the triaging of patients are well established in emergency medicine. The concept of triage dates back to the Napoleonic wars, and at its core is the assessment of a patient by an experienced person to determine the priority and timescale of treatment and intervention based on the severity of their condition. Over the years the concept of triage has become more scientific and a variety of tools utilising physiological data and algorithms have been developed to assist with effective triage.
It is well recognised from large national audits that existing systems failed to recognise or respond appropriately to early signs of critical illness. This in turn may lead to significant morbidity or mortality for the patient. Many such patients exhibit physiological derangement hours before their deterioration was detected by clinical staff and hospital systems. Evidence suggests that a large proportion of ward based patients receive substandard care prior to ICU admission and that 20–40% of such admissions are potentially avoidable. This number has decreased over the last 15 years, but remains significant.
In response to such findings, EWS have become increasingly prevalent across medicine globally over the past two decades to identify the deteriorating patient and to activate an appropriate response, the so called 'track and trigger' systems. Within the UK, there are many such systems in place across the NHS but most lack rigorous evaluation and validation. A recent postal survey also highlighted that there is great variability in how such EWS are utilised in EDs across the NHS.
The Royal College of Physicians of London, in its 2007 report 'Acute medicine: the right person, in the right setting—first time', recognised that a standardised EWS, used across the NHS could provide a step change in improving clinical outcomes in people with acute illness. A standardised NHS-wide NEWS would have advantages with regard to reliability of completion and promoting continuity throughout the patient's journey. However given the size of the NHS and diversity of work which is undertaken, any such tool is unlikely to perform well across all patient groups. This may give rise to false positives, or patients being falsely reassured by false negatives. There is some evidence that the use of EWS can predict need for hospital admission and mortality in ED patients. However, Roland and Coates suggested, in a recent commentary, that any such system proposed for the ED should be validated in ED patients. Other scoring systems such as the mortality in emergency departments sepsis (MEDS) score have been suggested as useful predictors of outcome in the ED. Although these scoring systems have a higher sensitivity, they rely on some laboratory investigations which necessitate a delay in obtaining the results. The NEWS also has the advantage that it is proposed to be used universally; therefore a diagnosis for the patient is not required in order to use the tool.
This study has several potential limitations. Among the group of patients selected for this analysis (N=2489), only 2003 could be assessed due to missing observations on attendance. This missing information was generally only one or two of the six required physiological data points, but prevented an accurate calculation of a NEWS value. No information is available for patients who attended and were discharged within 2 days of attendance. This group should by virtue of the fact that they are discharged within 2 days have a much lower incidence of significant illness. Our data only included ICU admission within 2 days, so we are unable to comment on patients who may have been admitted to the ICU later in their hospital admission. However, for our target group of ED patients at presentation it could be argued that ICU admission more than 2 days after ED attendance is less linked to features of illness present at initial ED presentation.
We only collected information on in-hospital mortality. No attempt was made to follow-up patients after discharge from hospital, so any patients who were discharged and died at home within 30 days are not included in our data. Our study did not record any information on patients' co-morbidity.
The data presented in this study show there is some promise for the use of a single EWS in the ED, when applied to a large cohort of patients with a potentially serious condition. Among patients who have sepsis, a single EWS of ≥7 in the ED indicates a 27% chance of requiring admission to the ICU within 48 h and/or death within 30 days. At this level, an argument can be made for mandating senior ED clinical review for all these patients. In addition, there could also be an argument for mandatory review by a critical care outreach team, regardless of ultimate destination. Our study only looked at patients with sepsis, so the generalisability to other serious conditions is unknown. However, given that sepsis is a common condition with potential significant morbidity and mortality but that also has a heterogeneous presentation, suggests that this approach may be more widely applicable and this potential warrants further research.
This concept also lends itself to extension to prehospital care and ambulance services. Most ambulance services routinely collect the physiological data required to calculate an EWS score, and indeed some ambulance services have incorporated this into electronic patient record forms. An agreed EWS score of greater than a specific level could be used as a trigger for ambulance service pre-alert of a receiving ED.
Point of care lactate testing has also been shown to be feasible in the ED. Serum lactate is recognised as an independent predictor of mortality in sepsis and there may be potential for combining EWS systems and point of care to further improve diagnostic accuracy for patients at risk of adverse outcomes in sepsis.
Discussion
Systems for the triaging of patients are well established in emergency medicine. The concept of triage dates back to the Napoleonic wars, and at its core is the assessment of a patient by an experienced person to determine the priority and timescale of treatment and intervention based on the severity of their condition. Over the years the concept of triage has become more scientific and a variety of tools utilising physiological data and algorithms have been developed to assist with effective triage.
It is well recognised from large national audits that existing systems failed to recognise or respond appropriately to early signs of critical illness. This in turn may lead to significant morbidity or mortality for the patient. Many such patients exhibit physiological derangement hours before their deterioration was detected by clinical staff and hospital systems. Evidence suggests that a large proportion of ward based patients receive substandard care prior to ICU admission and that 20–40% of such admissions are potentially avoidable. This number has decreased over the last 15 years, but remains significant.
In response to such findings, EWS have become increasingly prevalent across medicine globally over the past two decades to identify the deteriorating patient and to activate an appropriate response, the so called 'track and trigger' systems. Within the UK, there are many such systems in place across the NHS but most lack rigorous evaluation and validation. A recent postal survey also highlighted that there is great variability in how such EWS are utilised in EDs across the NHS.
The Royal College of Physicians of London, in its 2007 report 'Acute medicine: the right person, in the right setting—first time', recognised that a standardised EWS, used across the NHS could provide a step change in improving clinical outcomes in people with acute illness. A standardised NHS-wide NEWS would have advantages with regard to reliability of completion and promoting continuity throughout the patient's journey. However given the size of the NHS and diversity of work which is undertaken, any such tool is unlikely to perform well across all patient groups. This may give rise to false positives, or patients being falsely reassured by false negatives. There is some evidence that the use of EWS can predict need for hospital admission and mortality in ED patients. However, Roland and Coates suggested, in a recent commentary, that any such system proposed for the ED should be validated in ED patients. Other scoring systems such as the mortality in emergency departments sepsis (MEDS) score have been suggested as useful predictors of outcome in the ED. Although these scoring systems have a higher sensitivity, they rely on some laboratory investigations which necessitate a delay in obtaining the results. The NEWS also has the advantage that it is proposed to be used universally; therefore a diagnosis for the patient is not required in order to use the tool.
This study has several potential limitations. Among the group of patients selected for this analysis (N=2489), only 2003 could be assessed due to missing observations on attendance. This missing information was generally only one or two of the six required physiological data points, but prevented an accurate calculation of a NEWS value. No information is available for patients who attended and were discharged within 2 days of attendance. This group should by virtue of the fact that they are discharged within 2 days have a much lower incidence of significant illness. Our data only included ICU admission within 2 days, so we are unable to comment on patients who may have been admitted to the ICU later in their hospital admission. However, for our target group of ED patients at presentation it could be argued that ICU admission more than 2 days after ED attendance is less linked to features of illness present at initial ED presentation.
We only collected information on in-hospital mortality. No attempt was made to follow-up patients after discharge from hospital, so any patients who were discharged and died at home within 30 days are not included in our data. Our study did not record any information on patients' co-morbidity.
The data presented in this study show there is some promise for the use of a single EWS in the ED, when applied to a large cohort of patients with a potentially serious condition. Among patients who have sepsis, a single EWS of ≥7 in the ED indicates a 27% chance of requiring admission to the ICU within 48 h and/or death within 30 days. At this level, an argument can be made for mandating senior ED clinical review for all these patients. In addition, there could also be an argument for mandatory review by a critical care outreach team, regardless of ultimate destination. Our study only looked at patients with sepsis, so the generalisability to other serious conditions is unknown. However, given that sepsis is a common condition with potential significant morbidity and mortality but that also has a heterogeneous presentation, suggests that this approach may be more widely applicable and this potential warrants further research.
This concept also lends itself to extension to prehospital care and ambulance services. Most ambulance services routinely collect the physiological data required to calculate an EWS score, and indeed some ambulance services have incorporated this into electronic patient record forms. An agreed EWS score of greater than a specific level could be used as a trigger for ambulance service pre-alert of a receiving ED.
Point of care lactate testing has also been shown to be feasible in the ED. Serum lactate is recognised as an independent predictor of mortality in sepsis and there may be potential for combining EWS systems and point of care to further improve diagnostic accuracy for patients at risk of adverse outcomes in sepsis.
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