Consequences of ambulance diversion serious for patients with acute MI

Shen Y. JAMA. 2011;305:2440-2447.

Prolonged ambulance diversion caused by temporary closures of EDs due to overcrowding or lack of resources was associated with increases in mortality at 30 days, 90 days, 9 months and 1 year among a group of patients with acute MI, according to new data.

The study featured 13,860 Medicare participants from four California counties admitted for acute MI between 2000 and 2005. Researchers examined Medicare claims data and daily ambulance diversion logs, and determined the nearest ED for each patient’s ZIP code.

On average, the daily diversion duration for those analyzed was 7.9 hours. Overall, 11,625 patients had an ED with at least three of the four diversion exposure levels — no exposure (n=3,541), less than 6 hours (n=3,357), more than 6 hours but less than 12 hours (n=2,667), or at least 12 hours (n=2,060).

Among this population, researchers observed no significant differences in mortality between patients with no diversion exposure to those that had diversion exposure of less than 12 hours. However, for those exposed to more than 12 hours of diversion, all four measurements of unadjusted mortality were higher: 30 days (19% vs. 15%); 90 days (26% vs. 22%); 9 months (33% vs. 28%); and 1 year (35% vs. 29%).

These findings, researchers Yu-Chu Shen, PhD, and Renee Y. Hsia, MD, wrote in their study, “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 acute MI 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.”

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