Description of the event

The magnitude and severity of primary injuries from a blast explosion are determined by proximity, the quantity and type of explosive, and whether the explosion is in an open or enclosed space. Naturally, when an explosion occurs at a large gathering of people, other factors that strongly affect overall morbidity and mortality include access of rescuers to the injured and the personnel and resources available to care for an overwhelming number of victims in the immediate aftermath.

The increasing prevalence of terrorism and insurgency over the last three decades has increased our understanding of the types of injuries caused by blasts in the civilian environments—injuries once seen only on the battlefield—as well as the predictors of survival and the management techniques for such incidents. Primary blast injuries are uncommon by the time blast victims reach the hospital because most primary blast injuries result in immediate death. Because they are so rare, and because a bombing often results in so many casualties converging on a single institution, many physicians and other health care workers with no prior expertise in trauma or disaster management may be pressed into service to care for trauma patients.

Even though many articles in the medical literature describe the effects of blast injuries, and others describe medical planning and care for mass gatherings (i.e., mass “gatherings of potential patients” ), few combine both topics. Until recently, most of the literature concerning health care planning for mass gatherings ignored the risk of a major traumatic event such as a bombing, instead focusing on environmental or medical emergencies An incident in which 60,000 spectators are exposed to an exploding bomb demands a different response.

Fortunately, very few incidents of intentional or accidental explosions affecting large gatherings such as sporting or entertainment events (e.g., the Atlanta Olympics in 1996, Bali in 2002, and Boston Marathon in 2013) have occurred. The bombings at the finish line of the 2013 Boston Marathon illustrated just how easily amateurs with readily obtainable supplies can inflict significant damage to a civilian population. Many of the terrorist bombings from which we have learned about injury patterns occurred in other settings (i.e., U.S. barracks in Beirut 1983, the Murrah Federal Building 1995, the World Trade Center in New York in 1993, the Madrid train in 2004, and numerous attacks in Israel). By extrapolating from what is known about the nature of explosion injuries, the outcome of explosions that have affected many victims, and the strategies developed to provide medical care at major events, a workable strategy to care for these injuries can be built.

The medical usage rate (MUR; generally reported as numbers of patients per 10,000 in attendance) at a mass gathering is rarely greater than 50 at a spectator event, and it is most often related to weather. By stark contrast, one author documents a mortality of 7.8% for open-air and 49% for closed-space bombings (although these do not refer to mass gatherings with several thousand people in attendance).

In this chapter we present two different case presentations of explosions at mass gatherings that serve to illustrate the differences between low- and high-order explosives. One example, the Boston Marathon Bombing in April 2013, is a case where low-order explosives were used. These explosives (e.g., black powder, which is found in fireworks) typically do not detonate but instead burn rapidly. They can still produce a large amount of force. Our second case presentation examines an attack using high-order explosives, the bombing of a nightclub in Bali in 2002, with ammonium nitrate. These explosions do not burn but detonate. They generate high temperature and pressure gases that lead to a shock wave. Please refer to Chapter 71 for more details on the physics of blasts and blast injury patterns.

Pre-incident actions

Preparation for conventional explosions at a large gathering is best when it is preventative rather than reactive. The best preparations depend on making conditions unfavorable for the bomber and designing structures that are fire resistant, less likely to collapse, and that offer easy egress in the event of an explosion. Measures can be taken, as in the London Underground, to remove waste receptacles in which an explosive device may be hidden. Similarly, although inconvenient, inspecting the backpacks and the trunks of vehicles of those entering events has become a necessary precaution.

The importance of repeated drilling of all the facets of a hospital and region’s disaster plan must not be underestimated. Following the bombing at the 1996 Atlanta Olympics, Atlanta Emergency Medical Services leaders attributed pre-event training and drills practiced during the five years leading to the event as the principal reason why their response went well. All 111 injured patients were evacuated to the area hospitals within just 32 minutes of the explosion. To best prepare for a conventional bombing at a mass gathering, drill a scenario with a large surge of trauma victims, mixing both critically ill and lightly injured victims.

Post-incident actions

The potential volume of patients with both critical and noncritical injuries is the greatest risk to successful management of an explosion at a mass gathering. Establishing effective triage, both at the scene and again at the receiving hospitals, will prevent overwhelming limited resources and ensure that the most seriously injured patients are identified rapidly and sent to appropriate medical facilities.

Virtually all civilian bombings constitute a criminal act. Therefore, any material from the explosives found on or inside of victims is evidence that may be useful to investigational authorities to solve the crime. Salvaged clothing may contain identifiable explosive residue. Even corpses may yield important clues; consider performing postmortem x-rays to identify shrapnel. Expect to continue to work with law enforcement after an incident, especially in matters such as evidence collection, and as witnesses as the examining health care providers.

After treatment of casualties is completed, how should outcomes be assessed? Data points of interest include injury severity scores, specific injuries, morbidity, mortality, and location of individuals with respect to the explosive device. By publishing data such as these, as well as lessons learned, it may be possible to improve the response to the next bombing incident.

Medical treatment of casualties

When caring for victims of a conventional bombing at a mass gathering, keep in mind the convergence of two types of disasters: injuries unique to conventional explosives and the challenges of caring for the surge of many simultaneously injured patients. Those close to the actual explosion often will die or suffer serious injuries, but the majority of casualties will receive relatively minor injuries, frequently from flying debris. The other traumatic injuries likely seen will be those related to stampede from those trying to escape, or burns from a resulting fire. Despite the variety of serious injuries unique to blast injuries, the most common injuries among blast survivors involve standard penetrating and blunt trauma.

The major medical challenge in caring for the victims of bombs, in addition to the multiple simultaneous casualties, is to identify those who are seriously injured but salvageable, and to realize that they will be mixed in with a large number who are lightly injured or psychologically traumatized. Details concerning the nature, type, and care of injuries common to conventional explosions are available elsewhere in the book.