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An in-depth clinical review of the complex injuries common in the victims of bombings and explosions.

The April 2013 Boston Marathon bombings brought the sobering reality of domestic terrorism back to the United States. Yet amidst the carnage and chaos that followed the explosions emerged a superb response by the Boston EMS system and the emergency medicine community. The incident highlighted the need for all practicing emergency physicians to maintain a working knowledge of the clinical evaluation and management of patients with blast injuries. This article will summarize salient points from recent literature with emphasis on the 2013 LLSA article Blast Injuries by Wolf et al[1] and The Bombings: Injury Patterns and Care, a curriculum funded by the Centers for Disease Control (CDC) for which The American College of Emergency Physicians (ACEP) was the lead grantee[2].

Terrorism is defined by four conditions; it is premeditated, politically motivated, aimed at civilians, and perpetrated by sub-national groups. International attacks meeting that definition include the Madrid subway bombing in 2004, the London subway bombing in 2005, the Mumbai attack in 2006, and bombings in Tel Aviv in 2001 and 2006. In the United States, 324 criminal bombing events occurred between 1980 and 2001; the most notorious were the Oklahoma City bombing of the Murrah Federal Building in 1995 and the September 11, 2001 attacks on the World Trade Center in New York City and the Pentagon in Washington, DC. The number and lethality of terrorist attacks has been rising since the late 1990s (See Figure 1.[1])

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Figure 1: Worldwide trends in terrorist explosive events from 1999 to 2006 Data obtained from RAND®-MIPT Terrorism Incident Database.  (From Wolf et al.)

Improvised explosive devices (IEDs) have been commonly used in terrorist attacks. Categories of IEDs are car and truck bombs, letter and parcel bombs, pipe bombs, and backpack or satchel bombs. To increase the injuries and lethality of IEDs, perpetrators may add chemicals, radiological materials, or fragmenting items to the bombs. Scraps of metal, rocks, and ball bearings are effective for this purpose. Contaminated material such as feces has been included to precipitate infection and complicate wound healing. Chemicals like chlorine will release chlorine gas to induce pulmonary toxicity.  The September 2011 attacks were characterized as airplane incendiary bombs. Other terrorist weapons used are rocket propelled grenades (RPGs), surface to air missiles (SAMs), and enhanced blast devices. In the case of enhanced blast devices, an initial blast disseminates explosive material and then triggers a second explosion covering a much larger area[3].

Blast Physics
When an explosive detonates, the solid or liquid explosive material is instantaneously converted to gas which immediately expands outward displacing the surrounding medium. The blast wave arising from this phenomenon generates winds that create blast injury by propelling people and objects. The peak of the blast wave, called blast overpressure, is responsible for the range of injuries that occur. Blast energy dissipates rapidly in an open space correlating to the cube of the distance from the source. In an enclosed space, pressure waves reflect back from walls or other solid surfaces causing extensive injury to victims located close to those surfaces. Reflected pressure waves reverberating in an enclosed area raises the peak overpressure and the duration of the explosive effect resulting in exponential increase in the extent and lethality of injury. Leibovici et al. found a difference of 46% mortality in victims of two closed space bombings on buses compared to 7.8% in two open-air explosions[4]. Similar devices were used in all 4 incidents. (See Figure 2[2])

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Figure 2: Spheres of injury relative to distance from blast. (From Bombings: Injury Patterns and Care; Diagram used with permission of John-Phillipe Dionne, Ph.D.) 

Blast Injury Categories

1. Primary Blast Injuries
Primary blast injuries are caused by tissue damage sustained directly from the blast overpressure. Three mechanisms are described: spalling, shearing, and implosion. Spalling occurs when the blast wave moves from high-density tissues into low-density tissues causing molecular disruption and fragmentation of the higher density tissue into the lower density. The effect is similar to water being blasted into air causing a large splash and fragmentation of the water into the air. Shearing is the tearing of tissues that occurs when tissues of different densities move at different speeds. Implosion is caused when gasses in hollow organs are compressed by the blast pressure and then rapidly re-expand causing visceral disruption[1].

Primary blast injuries occur most frequently at the interface of air and tissue as the blast creates abrupt pressure changes. The most commonly injured organs are the ears secondary to tympanic membrane perforation, the lungs, and hollow viscera in the gastrointestinal tract. The tympanic membrane sustains damage at lower pressure than any other structure serving as a quick means of assessing patients for primary blast injury.  If the tympanic membranes are undamaged, it decreases the likelihood that other primary blast injury was sustained[3].

Pulmonary injuries are the second most commonly seen from the primary blast and the most common critical injury. Pulmonary hemorrhage, contusion, pneumothorax, pneumomediastinum, hemothorax, and arterial air embolism are manifestations of primary blast injury. Air embolism can cause stroke, myocardial or spinal cord infarction, infarction of other organ systems, and death. Chest radiographs of blast injury patients with suspected barotrauma may demonstrate a butterfly pattern created by bilateral perihilar infiltrates from pulmonary contusions.

The gastrointestinal system is the third most frequently injured as the direct result of the blast. The ileocecal region and the colon are at risk for perforation from the implosion mechanism and rapid shifts in air pressure. Intestinal contusions or hemorrhage may occur from barotrauma. Mesenteric ischemia occurs from shearing forces on the arterial supply or as a result of air embolism[1]. Ocular injuries including globe rupture, hyphema, retinitis, and conjunctival hemorrhage are less frequent primary blast injuries.

Myocardial contusion, hemorrhage, and atrial rupture have been described.

2. Secondary Blast Injuries
Flying debris created during the explosion causes secondary blast injuries. Terrorist bombs cause particularly devastating secondary injuries because they usually contain fragmenting items. These injuries are the most common cause of morbidity and mortality because their impact is felt far beyond the zone of primary blast injuries. Blunt and penetrating injuries may occur. Fractures, traumatic amputations, and soft tissue wounds are the most common secondary injuries. Foreign bodies may penetrate deeply into the body creating deceptively small entrance wounds. Emergency physicians should have a low threshold for imaging studies in victims of secondary blast injury[2].

3. Tertiary Blast Injuries
Tertiary injuries are sustained when victims are bodily displaced by the blast and thrown to the ground or against fixed objects. A second etiology of tertiary injuries is the collapse of buildings or structures. Head injuries, fractures, blunt trauma, crush injuries, compartment syndrome, and asphyxia are sustained as the result of tertiary blast injury. Mortality among victims trapped in collapsed structures increases sharply after 24 hours primarily because of untreated crush injuries and compartment syndrome[5].

4. Quaternary Blast Injuries
Injuries and illnesses directly related to the blast but not caused by the preceding three categories are considered quaternary. Environmental hazards created by the explosion such as smoke, fire, chemical exposure, and radiation cause quaternary injury. The exacerbation or destabilization of chronic diseases is covered in this category. Common quaternary injuries are burns, inhalation injuries, radiation sickness, asthma or COPD exacerbations, and acute coronary syndromes[1, 2].

Management Strategies
When an emergency department is notified of a blast or terrorist incident in the community, disaster procedures should be activated. Think about decontamination for victims. If you’re told about whether the blast was in a confined space (as opposed to open air), expect the number of critically injured patients to rise. Leibovici et al. reported that 22 of 52 surviving victims of 2 bus accidents required endotracheal intubation[4].

During the pre-hospital phase of care, military experts report positive experience with the liberal use of tourniquets for significant extremity hemorrhage. No adverse outcomes have been associated with tourniquet use. They recommend early application. Hemostatic dressings are used for non-extremity wounds. Pressure dressings are held in place for five minutes as patients are rapidly transported to the hospital[2].

Initial evaluation and stabilization of blast-injured patients is similar to other trauma patients: Assess and stabilize the airway, followed by breathing, circulation, neurologic assessment, and secondary survey. Patients identified as having pulmonary blast injury require careful management. Fluid resuscitation should be judicious and carefully monitored because excessive crystalloid can precipitate pulmonary edema. In patients with multiple injuries and crush syndromes, fluid management can be difficult – Renal perfusion must be maintained, but fluid overload avoided. The patient’s respiratory status should be optimized. Pain control is essential to allow comfortable respirations. Chest tubes should be placed early for management of pneumothoraces or hemothoraces. Non-invasive ventilatory strategies should be maximized before endotracheal intubation because positive pressure ventilation may increase pulmonary barotrauma and precipitate air embolism. If intubation is necessary, employ lung-protective strategies. A tidal volume of 5-7 mL/kg is an appropriate initial setting. Pressure controlled ventilation; permissive hypercapnia, positive end expiratory pressure (PEEP), and the acceptance of oxygen saturations above 90% are principles of ventilator management for the pulmonary blast injured patient. If air emboli are suspected, alternate strategies may be necessary: PEEP should be minimized, FiO2 of 100% is recommended to increase the absorption of air emboli, and Hyperbaric oxygen referral may be needed [1].

Management of other traumatic injuries follows the basic strategies employed by well-trained emergency physicians. Use bedside ultrasound to identify intra-abdominal bleeding, though CT is necessary to diagnose bowel contusions. Military experts in the management of blast injuries developed a tenet of avoiding the “deadly triad” of hypothermia, coagulopathy, and metabolic acidosis. Bleeding should be controlled and gross contamination removed or debrided. Uncontrolled bleeding is the leading preventable cause of death. An INR > 1.5 on arrival predicts the need for massive transfusion (MT). If MT is required, fresh thawed plasma is the best resuscitation fluid. The military has reported positive results with the use of fresh whole blood though it is not widely available in civilian settings [6]. Crystalloid should be minimized to avoid dilution of clotting factors, acidosis, and inflammation[2].

Orthopedic injuries require careful
assessment for evidence of compartment syndrome, particularly in patients with crush injuries. Military data reveal that 86% of fasciotomies in victims of combat casualty were carried out after blast injuries[7]. Patients with significant burns will require aggressive fluid resuscitation though this may exacerbate other blast injuries. They should be admitted or transferred to a burn center[1].

The screening of ambulatory, asymptomatic patients for primary blast injury can be easily accomplished by protocol. They require an otoscopic examination looking for injury or perforation of the tympanic membranes. Wolf et al. state that asymptomatic patients with no evidence of tympanic injury are very unlikely to have other occult primary blast injuries[1]. They can be discharged with precautions. Patients with tympanic membrane injury require further screening for serious pathology. Oxygen saturation should be monitored and a chest radiograph ordered. If the radiograph is normal and the oxygen saturation remains normal during a 6-8 hour observation period, the patient can be discharged with ear, nose, and throat follow-up and precautions to return for pulmonary or gastrointestinal symptoms. Patients with deteriorating oxygen saturations or the development of further symptoms require further evaluation and admission[3].

High-Risk Patient Categories
Pregnant victims of blast injury require special consideration. Direct fetal injury from the primary blast is uncommon because of the protection afforded by amniotic fluid. Placental abruption may occur, however, because of the shearing mechanism of primary blast injury. Patients in the second or third trimester require monitoring in labor and delivery and evaluation for fetal maternal hemorrhage. A low threshold for ultrasound should be maintained[1].
Children who are victims of terrorist attacks require more intensive care than adults with similar injuries. Pulmonary contusions are common and may be asymptomatic early in the clinical presentation. Israeli data shows that pediatric victims of terrorism have higher injury severity scores and longer lengths of stay than those with injuries unrelated to terrorism. If possible, they should be cared for in pediatric trauma centers[8].

Conclusion
The unfortunate reality in the United States is that emergency physicians should know how to manage survivors of a terrorist bombing. This summary of recent work has reviewed the pathophysiology of primary, secondary, tertiary, and quaternary blast injuries.  The application of trauma and critical care principles to management of victims based on recent military and civilian data is outlined. Early and aggressive control of hemorrhage, a lung protective strategy in patients with pulmonary blast injury, identification of crush injuries and compartment syndrome, and special attention to pregnant patients and children are general strategies in optimal management of the blast injured patient.

Laura Pimentel is a clinical associate professor of emergency medicine at the University of Maryland School of Medicine and the VP and CMO of the University of Maryland Emergency Medicine Network

 

References


1.    Wolf, S.J., et al., Blast injuries. Lancet, 2009. 374(9687): p. 405-15.
2.    Prevention, C.f.D.C.a. and A.C.o.E. Physicians, Bombings: Injury Patterns and Care.
3.    DePalma, R.G., et al., Blast injuries. N Engl J Med, 2005. 352(13): p. 1335-42.
4.    Leibovici, D., et al., Blast injuries: bus versus open-air bombings--a comparative study of injuries in survivors of open-air versus confined-space explosions. J Trauma, 1996. 41(6): p. 1030-5.
5.    Kuwagata, Y., et al., Analysis of 2,702 traumatized patients in the 1995 Hanshin-Awaji earthquake. J Trauma, 1997. 43(3): p. 427-32.
6.    Spinella, P.C., Warm fresh whole blood transfusion for severe hemorrhage: U.S. military and potential civilian applications. Crit Care Med, 2008. 36(7 Suppl): p. S340-5.
7.    Ritenour, A.E., et al., Complications after fasciotomy revision and delayed compartment release in combat patients. J Trauma, 2008. 64(2 Suppl): p. S153-61; discussion S161-2.
8.    Aharonson-Daniel, L., et al., Epidemiology of terror-related versus non-terror-related traumatic injury in children. Pediatrics, 2003. 112(4): p. e280.


When Jay Schuur read that a bomb had detonated at the Boston Marathon, he was a couple blocks from the emergency department...

Schuur, an emergency physician at Brigham and Women’s, was off duty and working on research when he saw the news about the bombing pop up online. 

“For about 30 seconds I thought about whether I should call over to the ED and see if they needed an extra hand. Then I decided to just walk over there. The first couple of patients had already arrived and the attending physicians who were on staff had already activated the hospital’s disaster plan and started organizing the physicians and nurses into a group of trauma teams. They already had enough teams in our two main treatment areas, so another physician and I went into our observation area and created additional space to see additional patients.”

Brigham and Women’s, one of the 27 hospitals that received the 264 wounded from the bombing, sits about a mile from where the bombs exploded, and patients began arriving within minutes.

“Our disaster plan was activated immediately. The plan summons a number of hospital officials to come to the site and serve as incident commanders, but that took a few minutes. In the meantime the physicians and nurses on shift realized right away that there was the potential for many injured patients, so they took two steps that were critical. First, they started to clear out patients. It was a Monday afternoon and the ED was full. But by notifying the inpatient medicine teams and psychiatry group, they were able to open up capacity. The second great move was organizing the providers into a number of teams. We are very well equipped to take care of two or three trauma cases when they come in normally, but at one point I think we had eight or ten active trauma patients simultaneously, 8 of whom went to the operating room. A lot of people showed up in the ED and the teams helped them know how to plug in.”

Minutes after Schuur and his colleague opened up the observation unit, they received two critically injured patients. Thankfully, one of the patients arrived with a group of friends who were nurses. One nurse was actually an emergency nurse from Brigham and Women’s, and was immediately able to begin assisting in treatment.

After the initial assessment and stabilization, Schuur and his team notified the surgeons. The orthopedic surgeons had formed a couple of teams and went around the ED, assessing patients and creating a surgery priority list.

“There was a sort of “silent busyness” in the ED,” Schuur recalls. “There were lots of people and everyone was trying to find something to do. That was the initial mood, and then it switched to an apprehension about what might come next.”

By the end of the day the Brigham team cared for 26 victims of the bombing. According to Ron Walls, chairman of the emergency department, while his team had never seen anything like this before, they’d practiced drills over and over, and felt prepared.

 

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