What’s New in the Patient Safety World
March 2012
Value of an Expanded Early Warning System Score
Use of early warning scores (EWS) has never really caught on in the US. Yet we all agree that earlier recognition of clinical deterioration is critical and needs improvement (see our Patient Safety Tips of the Week for December 29, 2009 “Recognizing Deteriorating Patients”, March 15, 2011 “Early Warnings for Sepsis” and Februrary 22, 2011 Patient Safety Tip of the Week “Rethinking Alarms”).
The modified early warning score (MEWS) is probably the best known of these tools designed to alert staff to early clinical deterioration.
An expanded version of the MEWS was introduced in the Netherlands in 2009. A recent study (Smith 2012) now reports the impact of that score in predicting clinical deterioration in patients admitted to general or trauma surgery wards. The tool included the basic parameters included in earlier versions of the MEWS (heart rate, systolic BP, respiratory rate, oxygen saturation, temperature, and level of consciousness) but added some new parameters. One was urinary output. The other was a more subjective parameter: the nurse’s level of concern about the patient’s condition.
The authors looked at 592 consecutive patients admitted to the general and trauma surgery wards of a level I trauma center in the Netherlands. Overall, 8% of patients met their composite outcome of death, reanimation (resuscitation), unexpected ICU admission, emergency operation, or severe complication. Patients reaching a score of 3 or higher on the expanded tool were 11 times more likely to meet the composite endpoint, even after adjustment for the ASA grade. The negative predictive value of the score was 97%, indicating its use as a screening tool is quite valuable. The sensitivity was 74% and the positive predictive value 26%.
So how was the tool used? Three times a day, on clinical rounds, the score was recorded. In addition, a score was recorded any time clinical deterioration was noted. If the score was 3 or higher, nursing would advise evaluation by the attending physician and ask for a treatment plan. If that plan was unsuccessful, the ICU physician would be asked to evaluate the patient. The researchers are in the process of determining the impact of the expanded tool on adverse outcomes.
The commentary accompanying the study notes that the average age of the patients was 50 and that it would be useful to know if the scoring tool was as effective in older and younger patients. Also pointed out was that these were all surgical patients, so it is not known whether similar utility would apply to nonsurgical patients.
The concept that no single sign or parameter is likely to readily identify all patients who are deteriorating and that we need a more global assessment of multiple paramters is a good one. The MEWS and its offshoots show us the potential of such scoring systems to identify earlier those patients who are at risk of deterioration. In our December 29, 2009 Patient Safety Tip of the Week “Recognizing Deteriorating Patients” we noted that MEWS was a good start to the concept that monitoring multiple parameters simultaneously and integrating them to provide a “bigger picture” that might be potentially valuable. MEWS began as a paper-based system but with the introduction of more sophisticated physiologic monitoring systems and more widespread us of electronic medical records, the concept of rules-based algorithms running in the background and generating alerts to clinicians has become a reality. With more advanced physiologic monitoring capabilities it is likely that eventually we will have algorithms that incorporate multiple parameters to identify patterns indicative of deterioration that needs more immediate intervention. We’ve previously discussed difficulties in early detection of patient deterioration (see our Februrary 22, 2011 Patient Safety Tip of the Week “Rethinking Alarms”). In that column we highlighted a very insightful study by Lynn et al (Lynn 2011) that described many of the flaws in current patient monitoring systems, particularly those monitoring for respiratory complications. And we stressed the need for “smart” alarm systems that can monitor multiple parameters in an integrated fashion to detect deterioration earlier.
There remains a paucity of randomized controlled trials evaluating use of tools for the identification of deteriorating patients. A recent review by the Canadian Agency for Drugs and Technology in Health could find none but had a good bibliography of 10 non-randomized controlled studies (CADTH 2011).
Nevertheless, despite all the potential merits of technological solutions, we like the idea that the expanded MEWS in the Netherlands study also used what we consider a most valuable measure: the nurse’s bedside gestalt of the patient’s condition!
References:
Smith T, Den Hartog D, Moerman T, et al. Accuracy of an expanded early warning score for patients in general and trauma surgery wards. British Journal of Surgery 2012; 99: 192-197
Lynn LA, Curry JP. Patterns of unexpected in-hospital deaths: a root cause analysis. Patient Safety in Surgery 2011, 5:3 (11 February 2011)
http://www.pssjournal.com/content/pdf/1754-9493-5-3.pdf
CADTH (Canadian Agency for Drugs and Technology in Health). Tools for the Early Identification of Adult Inpatients at Risk for Deterioration: Clinical Evidence and Guidelines. 22 November 2011
http://cadth.ca/media/pdf/htis/nov-2011/RB0442-000%20Deterioration%20Screening.pdf
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