Diversion of ALS ambulances: characteristics, causes, and effects in a large urban system

To characterize the reasons for and effects of diversions of advanced life support (ALS) ambulances in a large urban area with a high concentration of receiving hospitals.

A retrospective study was performed in a large urban region during a consecutive three-month period. Diversion was defined as the ALS transport of a patient to an emergency department (ED) other than the designated primary receiving facility. Case-matched concurrent cohorts of patients who were and were not diverted were studied to establish emergency medical services (EMS) time intervals, including total prehospital interval (TPI), on-scene interval (OSI), and patient transfer interval (PTI); age; gender; Glasgow Coma Score (GCS); ALS interventions; and insurance status. The reasons for diversion and the chief complaints of diverted patients were also studied.

During the study period, 2,534 ALS runs occurred, of which 147 (5.8%) were diverted. Twenty-four (16.3%) diversions had incomplete run times, leaving 123 (83.7%) for analysis. The most common chief complaints of diverted patients were shortness of breath (SOB), chest pain (CP), and altered mental status (AMS). The most common reason for diversion was special consideration (SC), defined as a diversion requested by a patient, family member, law enforcement officer, or private medical doctor. Diverted ambulances had significant increases in TPI, 36.4 [95% confidence interval (95% CI) 35.1-37.7] vs. 33.4 [95% CI 32.13-34.7], and PTI, 10.3 [95% CI 9.4-11.2] vs. 7.9 [95% CI 7.2-8.6], compared with nondiverted ambulances. Further analysis demonstrated that SC diversions accounted for all of the increases in TPI (p<0.001) and PTI (p<0.001) when compared with other types of diversions and nondiverted transports.

"Special consideration" was the most common reason for diversion in this study. Special consideration diversions increased TPI and PTI, causing delays in arrival to the ED and decreased ALS ambulance availability.