Expect 2 waves of patients after terrorist attack

A study conducted after the bombing of the federal building in Oklahoma has revealed a misconception. Contrary to what most experts believed previously, there are actually two waves of patients after a terrorist attack, explains David Hogan, DO, FACEP, interim chair of the department of emergency medi cine at the University of Oklahoma College of Medicine and the study’s principal investigator.1

Here’s what to expect if a terrorist attack occurs in your community:

• First wave.

After a mass casualty incident, the majority of patients arrive by means other than ambulance, says Hogan. "The patients who are able to extricate themselves from the scene and secure their own transport to EDs tend to be the less injured. As a result, the first group of patients arriving to an ED tend to be of less severity than those arriving somewhat later."

This phenomenon was supported by the study of the Oklahoma bombing. "The more seriously injured cases arrived later," he says.

However, the first wave of patients may put staff at risk for contamination, he warns. "These patients typically have not typically received scene evaluation [or decontamination], which may be very important for a hazardous materials event."

Decontamination is not usually effective or needed for biowarfare agents delivered by aerosol, Hogan says.2-3 "However patients arriving in this first wave with hazardous materials or chemical warfare agent exposure will likely not have been decontaminated. Therefore, each hospital needs to have the ability to decontaminate these patients." (For more information on patient decontamination, see ED Manage ment, November 1999, p. 121, and September 1996, p. 105.)

• Second wave.

When the first wave of patients arrives at the ED, they should be triaged to various locations in the hospital to make way for the second wave. "Consideration needs to be given to the potential of a second wave of more seriously injured patients that may arrive a short time later," says Hogan.

"There should be clear plans as to the distribution of minimal casualties within the hospital to designated areas. These areas may be staffed with a variable cadre of physicians," he explains.

However, the designated area should be supervised by a physician skilled in the evaluation and treatment of traumatic wounds and disaster-related disorders, he recommends.

"The two-wave’ phenomenon will be modified by the type of disaster, location of the specific hospital in relation to the disaster, as well as other factors."


1. Hogan DE, Waeckerle JF, Dire DJ, et.al. Emergency department impact of the Oklahoma City terrorist bombing. Ann Emerg Med 1999; 34:160-167.

2. U.S. Army Medical Research Institute of Infectious Diseases. Medical Management of Biological Casualties Handbook, 2nd ed. Fort Detrick, Fredrick, MD: USAMRIID; 1996.

3. Franz DR, Jahrling PR, Friedlander AM, et al. Clinical recognition and management of patients exposed to biologic warfare agents. JAMA 1997; 278:399-411.

David Hogan, DO, FACEP, Department of Emergency Medicine, University of Oklahoma Health Sciences Center, Room EB 328, P.O. Box 26307, Oklahoma City, OK 26307. Telephone: (405) 271-5135. Fax: (405) 271-7007. E-mail: David-Hogan@OUHSC.EDU.