Temporary ED Closures Raise Mortality in AMI Patients

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When emergency departments (EDs) are temporarily closed to ambulance traffic, diverting patients with acute myocardial infarction (AMI) to the nearest available facility contributes to increased early and late mortality, according to a study in the June 15, 2011, issue of the Journal of the American Medical Association. However, the increased death rate was only seen when the diversion lasted for 12 hours or more.

Using Medicare claims data from January 2000 through November 2006 and detailed daily diversion logs from 4 large California counties, Yu-Chu Shen, PhD, of the Naval Postgraduate School (Monterey, CA), and Renee Y. Hsia, MD, MSc, of San Francisco General Hospital (San Francisco, CA), reported on 11,625 AMI patients taken to hospitals via ambulance.

The researchers measured the percentage of AMI patients who died within 7 days, 30 days, 90 days, 9 months, and 1 year from admission according to how long ambulance diversion lasted during temporary closure of the ED.

Longer Diversion More Detrimental

The average daily diversion lasted 7.9 hours, with a seasonal peak seen during winter months. Mortality rates for AMI patients were highest at all post-event time frames when the nearest ED experienced a diversion of 12 or more hours. There were no significant differences in mortality rates from 30 days to 12 months after admission between no diversion and a diversion that lasted less than 12 hours (table 1).

Table 1. Mortality According to Time from Admission and Duration of Diversion

Patient demographics and comorbid conditions were similar among diversion levels, with the exception that more black patients were in the 12-hour-plus category.

Importantly, patients in the longest diversion time category were less likely than those who experienced no diversion to receive catheterization (42% vs. 49%) and PCI (24% vs. 31%) once they arrived at the hospital. In addition, when the closest ED was on diversion for at least 12 hours, a smaller proportion of patients were admitted to hospitals with a catheterization laboratory compared with during times of no diversion (78% vs. 87%), suggesting that hospitals with catheterization facilities are on diversion more often than hospitals with no catheterization facilities.

The researchers also found that when the nearest ED was on a diversion lasting at least 12 hours, more patients were admitted to for-profit hospitals (17% vs. 7%) and to government hospitals (12% vs. 9%) than when the same ED was not on diversion.

Long Diversions Common But Avoidable

“When a hospital’s ED is on diversion, it can affect different types of patients—those patients who were diverted, those patients receiving care or admitted while the ED is on diversion status, and those patients in nearby hospitals receiving the diverted patients,” the study authors write.

Although mortality was only affected when the diversion time was 12 hours or more, Drs. Chen and Hsia say the estimated 3.24% increase in 30-day death experienced by patients in that category contributed to a 21.6% increase in mortality for the overall population.

Moreover, diversions of 12 hours or more were not uncommon, occurring in 25% of the daily logs.

“Notably, such long diversion hours are more likely to occur in winter and in densely populated metropolitan areas—both factors associated with increased ED demand,” the study authors write. “These findings point to the need for more targeted interventions to appropriately distribute system-level resources in such a way to decrease crowding and diversion, so that patients with time-sensitive conditions such as AMI are not adversely affected.”

According to the American College of Emergency Physicians (ACEP), hospitals can and should do more to avoid the necessity of diversions.

“The key is increasing flow through emergency departments by moving patients who have been admitted to the hospital out of the emergency department to inpatient areas,” said ACEP president Sandra Schneider, MD, in a press release.

The organization also has proposed the following recommendations:

• Coordinating the discharge of hospital patients before 12:00 noon. Research shows that timely departure from the hospital can significantly improve the flow of patients in EDs by making more inpatient beds available to emergency patients.
• Coordinate the scheduling of elective patients and surgical cases. Studies demonstrate that the uneven influx of elective patients (heaviest early in the week) is a prime contributor to exceeding capacity. This often requires support services to be available 7 days a week.

 

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Source:
Shen Y-C, Hsia RY. Association between ambulance diversion and survival among patients with acute myocardial infarction. JAMA. 2011;Epub ahead of print.

 

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