JAMA: Diverting ambulances from EDs linked with increased death for MI patients

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Among Medicare patients who experienced a heart attack in four California counties, when the nearest nearest emergency department (ED) diverts ambulance traffic for 12 hours or more, it was associated with an increased risk of death for up to one year, according to a study in the June 15 issue of Journal of the American Medical Association, which was released early online to coincide with its presentation at the AcademyHealth annual meeting in Seattle.

Recent reports have described the state of EDs in the U.S. as reaching a breaking point, with the ED system experiencing increased utilization but decreased capacity. These trends have led to problems for patients, such as longer wait times, overextended staff and disruptions to ambulance services, according to the study authors. Ambulance diversion, a practice in which EDs are temporarily closed to ambulance traffic due to overcrowding or lack of available resources, might be especially problematic for patients experiencing time-sensitive conditions, such as acute MI (AMI). However, they noted that there is “little empirical evidence” to show whether diversion is associated with worse patient outcomes. 

Therefore, Yu-Chu Shen, PhD, of the Naval Postgraduate School, Monterey, Calif., and National Bureau of Economic Research, Cambridge, Mass., and Renee Y. Hsia, MD, of the University of California, San Francisco conducted a study to examine whether temporary ED closure on the day a patient experiences AMI was associated with increased mortality.

The study included 13,860 Medicare patients with AMI within four California counties (Los Angeles, San Francisco, San Mateo and Santa Clara) who were admitted between 2000 and 2005. Data included 100 percent Medicare claims data that covered admissions between 2000 and 2005, linked with date of death until 2006, and daily ambulance diversion logs from the same four counties. 

The researchers identified 149 EDs as the nearest ED to these patients. Among the outcomes measured were the percentage of patients with AMI who died within seven days, 30 days, 90 days, nine months and one year from admission (when their nearest ED was not on diversion and when that same ED was exposed to less than six, six to less than 12, and 12 or more hours of diversion out of 24 hours on the day of admission).

Between 2000 and 2006, the study found the average daily diversion duration was 7.9 hours. The analysis included 11,625 patients and among these patients, 3,541, 3,357, 2,667 and 2,060 were admitted for AMI when their closest ED was not exposed to diversion and was exposed to less than six hours, six to less than 12 hours, and 12 or more hours, respectively. 

Shen and Hsia also found that 29 percent of patients in the no diversion category died within one year of ED admission, and the number of patients who died within one year of admission in the less than six hours, six to less than 12 hours and 12 or more hours diversion categories were 31 percent, 30 percent and 35 percent, respectively.

There were differences in treatment patterns for patients once admitted: the number of patients receiving catheterization was 42 percent among those in the 12 hours or greater ED diversion exposure category versus 49 percent in the no diversion category; and number of patients receiving PCI was 24 percent in 12 hours or greater exposure category versus 31 percent in the no diversion category.

Analysis of data indicated that there were no statistically significant differences in mortality rates between no diversion status and when the exposure to diversion was less than 12 hours. However, exposure to 12 or more hours of diversion, compared to no diversion, was associated with higher mortality rates at 30 days (19 percent vs. 15 percent); 90 days (26 percent vs. 22 percent); nine months (33 percent vs. 28 percent); and one year (35 percent vs. 29 percent). 

"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. It is important to emphasize that while demand on emergency care is increasing as evidenced by increasing utilization, supply of emergency care is decreasing. If these issues are not addressed on a larger scale, ED conditions will deteriorate, having significant implications for all," the authors wrote.

They added that possible policy