Ambulance diversion linked to AMI death rates as ER's become strapped

Kathleen Blanchard's picture
Ambulance diversion
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Is supply and demand to blame for ambulance diversion?

Researchers say emergency visits are up, but supply of emergency care is down, leading to ambulance diversion. A new study finds higher death rates among patients with acute myocardial infarction is associated with the practice of closing emergency rooms to ambulance traffic.

The cost of diversion of ambulances when emergency room staff is at a minimum, admission beds are full and ER patient load is too high was investigated by Yu-Chu Shen, Ph.D., of the Naval Postgraduate School, Monterey, Calif., and National Bureau of Economic Research, Cambridge, Mass., and Renee Y. Hsia, M.D., M.Sc., of the University of California, San Francisco.

The researchers found diverting ambulance traffic to the next hospital for twelve hours or more was associated with a 35 percent higher chance of death within a year for patients with heart attack, or acute MI (AMI).

Compared to the no diversion group, death within 30 days was 19 percent for patients rerouted due to emergency room closures of 12 hours or more, versus 15 percent; 26 percent higher at 90 days, versus 22 percent when patients were taken to the nearest ER and 33 vs. 22 percent after 9 months.

The study finding was taken from records of 11,625 Medicare patients with AMI within 4 California counties, between 2000 and 2005.Twenty-nine percent in the no ambulance diversion category died within a year of admission – 1034 patients.

The patients received the same treatment whether they were taken to a further hospital or not, showing no statistical differences in care received on hospital arrival.

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The authors say the findings are noteworthy and should be addressed; suggesting banning ambulance diversion; instituted in Massachusetts in 2009.

Supply of emergency care needs to be addressed

“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 write.”

The researchers also say it is important to find resources within the hospital system to prevent emergency room crowding and ambulance diversion, which is especially important for patients in need of rapid intervention.

The authors cite two studies targeting the declining state of emergency room care in the United States by the Robert Wood Johnson Foundation and a report by the Institute of Medicine, noting ER’s may be reaching a breaking point.

The authors caution, “We cannot disentangle the precise mechanisms through which diversion affects patient outcomes. Our results should not be interpreted as causal.” In the study, zip codes were used to ascertain the nearest emergency department.

The study only found an association between ambulance diversion and higher patient deaths from heart attack that needs further study.

Rates of death were explored within 7 days, 30 days, 90 days, 9 months, and 1 year. The link between higher death rates from AMI during times of emergency room ambulance diversion was “strong” and may even be “conservative”, conclude the authors.

JAMA: doi:10.1001/jama.2011.811
“Association Between Ambulance Diversion and Survival Among Patients With Acute Myocardial Infarction”
Yu-Chu Shen, PhD; Renee Y. Hsia, MD, MSc

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