Background: A prevalent assumption in hospital emergency preparedness planning is that patient arrival from a disaster scene will occur through a coordinated system of patient distribution based on the number of victims, capabilities of the receiving hospitals, and the nature and severity of illness or injury. In spite of the strength of the emergency medical services system, case reports in the literature and major incident after-action reports have shown that most patients who present at a health care facility after a disaster or other major emergency do not necessarily arrive via ambulance. If these reports of arrival of patients outside an organized emergency medical services system are accurate, then hospitals should be planning differently for the impact of an unorganized influx of patients on the health care system. Hospitals need to consider alternative patterns of patient referral, including the mass convergence of self-referred patients, when performing major incident planning.

Methods: We conducted a retrospective review of published studies from the past 25 years to identify reports of patient care during disasters or major emergency incidents that described the patients' method of arrival at the hospital. Using a structured mechanism, we aggregated and analyzed the data.

Results: Detailed data on 8303 patients from more than 25 years of literature were collected. Many reports suggest that only a fraction of the patients who are treated in emergency departments following disasters arrive via ambulance, particularly in the early postincident stages of an event. Our 25 years of aggregate data suggest that only 36% of disaster victims are transported to hospitals via ambulance, whereas 63% use alternate means to seek emergency medical care.

Conclusions: Hospitals should evaluate their emergency plans to consider the implications of alternate referral patterns of patients during a disaster. Additional consideration should be given to mass triage, site security, and the potential need for decontamination after a major incident.

(Disaster Med Public Health Preparedness. 2010;4:226-231)