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Expanded MEWS is more predictive
Updates seen as more appropriate for ED
Many facilities and EDs use the tool called the modified early warning score (MEWS), which includes questions about the patient's health state, to determine if patients are getting sicker and if they require transfer to the intensive care unit (ICU). However, researchers led by Chadwick Miller, MD, MS, assistant professor and director of clinical research in the Wake Forest University Department of Emergency Medicine in Winston-Salem, NC, believed that MEWS was not completely appropriate for the ED setting. They set out to prove it.
They reviewed records from 280 patients being admitted to the Wake Forest Baptist Hospital from the ED. Using MEWS, 82% of the patients fell into the category of "intermediate risk," a gray area where it can be unclear whether a higher or a lower level of care is needed. MEWS predicted that 18% of those patients required intensive care, but a look back at patients' records told the team that, in fact, 27% of the patients ultimately needed a higher level of care.
The team decided to make some additions to MEWS and then see if its predictive ability was improved. In its original form, MEWS looks at the following factors: systolic blood pressure, heart rate, respiratory rate, temperature, and the Glasgow Coma scale. Each value is given a score, and a total score of 5 indicates likelihood of death and transfer to the ICU. The researchers added the following variables: whether the patient arrived at the ED via ambulance, received intravenous antibiotics in the ED, the patient's length of stay in the ED, and gender.
"We thought patients who were brought to the ED by ambulance were probably more ill, and that this could predict patients who would need a higher level of care," Miller explains. "Patients who received intravenous antibiotics in the ED, or who had infectious illness, would probably be more likely to decompensate." The patient's length of stay likely would indicate those who were more ill, he adds, and gender also "proved to have some predictive ability."
When they reviewed the same charts again using what they call MEWS Plus, the researchers found that about 22% more patients were placed in an appropriate risk category than had been using the original MEWS model.
Corey R. Heitz, MD, assistant professor in the Department of Emergency Medicine, Boonshoft School of Medicine, Wright State University, Kettering, OH, says the weakness of MEWS is that it does not have sufficient low-risk criteria, resulting in a "huge middle ground."
"Initial studies on MEWS looked at the time of ED presentation. Unfortunately, people stay in the ED for a period of time, and things can happen there," Heitz notes. "What happens is at some point in time problems may have been corrected, and the patient may not need the ICU anymore." Conversely, he notes, the original score might say the patients does not need the ICU, but he or she could end up getting worse.
Don't be in rush to use MEWS Plus
While the researchers who developed an expanded version of the modified early warning score (MEWS), or MEWS Plus, for use in the ED showed that it had greater predictive ability than the original MEWS, they caution ED managers about using the newer version immediately.
They note that the 280 patient charts on whom they performed reviews represented too small a sample to justify wide adoption of MEWS Plus.
"At this point, I do not think any of the information is ready to be put to use, but they can understand this research is going on and that in the future there may be a better way of making those distinctions," says Corey R. Heitz, MD, assistant professor in the Department of Emergency Medicine, Boonshoft School of Medicine, at Wright State University, Kettering, OH.
ED physicians do a lot of "clinical gestalt," so it's nice when they can be backed up by numbers, "and in the future, we may have numbers we can attach to that gestalt," Heitz says.
Chadwick Miller, MD, MS, assistant professor and director of clinical research in the Wake Forest University Department of Emergency Medicine in Winston-Salem, NC, also was cautious. "Yes, the revised model needs to be further validated," Miller says. Several items need to go into the decision of whether to send an ED patient to the ICU, and a lot of those items are not captured in the MEWS, so perhaps the questions they added may be considered, he says.
Miller adds, however, that there are other factors to consider as well. "In your mind, you summarize the entire ED course and try to predict how the patient will do in a day or two," he says. "There are a lot of intangibles involved."