Likelihood of reroute during ambulance diversion periods in central Maryland

To determine the proportion of patients rerouted during ambulance diversion periods and factors associated with reroute.

A retrospective cohort design was used to examine reroute practices of prehospital providers in central Maryland in 2000. Ambulance transport and diversion data were merged to identify transports that occurred during diversion periods. The proportion of patients rerouted when the closest hospital was on diversion was determined. Generalized estimating equation modeling identified patient, transport, and hospital factors that influenced the likelihood of reroute.

Central Maryland hospitals were on diversion 25% of the time in 2000, although it varied by hospital (range of 1-34%). There were 128,165 transports during the study period, of which 18,633 occurred when the closest hospital was on diversion. Of these, only 23% were rerouted. More than half of all transports during a diversion period (53%) occurred when multiple neighboring hospitals were also on diversion. The factors that influenced the likelihood of reroute the most were hospital-related factors. Large volume hospitals and hospitals that spent more time on diversion were less likely to have transports rerouted to them.

Rerouted transports more frequently go to lower volume, less busy hospitals. However, only a small proportion of patients were rerouted. Prehospital providers have limited options because often when one hospital is on diversion, other nearby hospitals are as well. Although ambulance diversion may be an important signal of hospital distress, in this region it infrequently resulted in its intended outcome, rerouting patients to less crowded facilities.