Blast Injuries 

Updated: Feb 14, 2016
Author: Andre Pennardt, MD, FACEP, FAAEM, FAWM; Chief Editor: Trevor John Mills, MD, MPH 

Overview

Practice Essentials

Blast injuries result from explosions that have the capability to cause multisystem, life-threatening injuries in single or multiple victims simultaneously. These types of events present complex triage, diagnostic, and management challenges for the health care provider.

Blast injuries are generally categorized as primary to quaternary. Primary injuries are caused by the effect of transmitted blast waves on gas-containing structures; secondary injuries, by the impact of airborne debris; tertiary injury, by the transposition of the entire body because of blast wind or structural collapse; and quaternary injuries, by all other forces.[1]

Primary blast injury is organ and tissue damage caused solely by the blast wave associated with high-order explosives. See the image below.

Blast injuries. Idealized graph of a blast pressur Blast injuries. Idealized graph of a blast pressure wave over time. Courtesy of Bowen TE and Bellamy RF, eds, Emergency War Surgery. Washington, DC: United States Government Printing Office, 1988.

Signs and symptoms

Blast injuries are divided into the following 4 categories:

  • Primary: caused solely by the direct effect of blast overpressure on tissue

  • Secondary: caused by flying objects that strike people

  • Tertiary: caused by high-energy explosions; occurs when people fly through the air and strike other objects

  • Quaternary: encompass all other injuries caused by explosions

Unique patterns of injury are found in all blast types. The lungs, bowel, and middle ear are most susceptible to primary blast injuries (PBIs).

Pulmonary barotrauma, the most common fatal PBI, may include the following:

  • Pulmonary contusion

  • Systemic air embolism, which most commonly occlude blood vessels in the brain or spinal cord

  • Free radical–associated injuries such as thrombosis, lipoxygenation, and DIC

  • Impaired pulmonary performance lasting hours to days

  • ARDS may be a result of direct lung injury or of shock from other body injuries

Acoustic barotrauma consists of the following:

  • Tympanic membrane rupture (most common)

  • Hemotympanum without perforation

  • Ossicle fracture or dislocation may occur with very high-energy explosions

Thoracic PBI produces the following unique cardiovascular response:

  • A decrease in heart rate, stroke volume, and cardiac index

  • The normal reflex increase in systemic vascular resistance does not occur, so blood pressure falls

  • If this response is not fatal, recovery usually occurs within 15 minutes to 3 hours

See Clinical Presentation for more detail.

Diagnosis

Lab tests

Lab tests are essential for accurate diagnosis in the mass-casualty situation. Considerations include the following:

  • Do not overwhelm the laboratory with screening or protocol laboratory tests of little clinical benefit

  • Most patients injured by significant explosions should have a screening urinalysis

  • If the explosion occurred in an enclosed space or was accompanied by fire, test carboxyhemoglobin (HbCO) and electrolytes to assess acid/base status

  • Pulse oximetry readings may be misleading in cases of CO poisoning

  • Victims of major trauma should have baseline hemoglobin determinations, crossmatching for potential blood transfusion, and screening for disseminated intravascular coagulation (DIC)

Imaging studies

Indications for chest radiography are as follows:

  • History of exposure to high overpressure

  • Tympanic membrane rupture

  • Respiratory symptoms

  • Abnormal findings on chest auscultation

  • Visible external signs of thoracic trauma

If significant abdominal pain is present, consider an immediate abdominal radiographic series (flat and upright films) or abdominal CT to detect pneumoperitoneum from enteric rupture. Intestinal barotrauma is more common with underwater than air blast injuries.

Focused Abdominal Sonography for Trauma (FAST) is a potentially useful tool for rapidly screening patients, especially in the setting of multiple seriously injured victims. A positive FAST examination in an unstable patient is an indication for surgical exploration of the abdomen in the operating room. A negative FAST examination is unreliable in the setting of penetrating trauma to the abdomen, flank, buttocks, or back, and it should be followed up with CT examination of the abdomen and pelvis.

See Workup for more detail.

Management

Prehospital care

  • Screen for radioactive contamination with a hand-held Geiger counter for any explosion that may involve radioactive material, including any explosion that may have been deliberately set; if radioactive material is detected, decontamination of personnel and equipment as well as notification of the receiving hospital is required

  • Rapidly identify patients with life-threatening external hemorrhage and control bleeding; early use of tourniquets may be life-saving, especially in the setting of multiple seriously injured casualties

  • High-flow oxygen should be administered to all patients with respiratory distress, abnormal findings on auscultation, and evidence of significant thoracic trauma

  • Avoid administration of large quantities of IV fluid in patients with a high suspicion of ongoing internal hemorrhage; judicious fluid boluses may be required if patients exhibit signs and symptoms of inadequate perfusion, such as deteriorating mental status

  • Initiate measures to reduce heat loss and prevent hypothermia

Emergency department care

  • Penetrating wounds (secondary blast injury), blunt trauma (tertiary/secondary blast injury), and burns receive standard treatment

  • Shrapnel wounds (secondary blast injury) are treated as low-velocity gunshot wounds

  • Hemodynamically unstable patients with significant trauma may benefit from early use of packed red blood cells (PRBC) and fresh frozen plasma (FFP) in a 1:1 ratio, as well as platelets

  • Consider early use of fresh whole blood if available

  • In patients with severe trauma, also consider cryoprecipitate and recombinant factor VIIa

  • In patients with traumatic brain injury, prevention of hypoxia and hypotension is critical

  • Because pulmonary contusion tends to evolve over several hours, a period of observation and repeat radiography may be necessary if indicated; definitive airway management and ventilatory support may be required

  • If abdominal pain persists or vomiting develops, consider admitting the patient for observation, as intestinal hematoma may be difficult to detect in the ED

  • In patients with open wounds from blasts, consider broad-spectrum prophylactic antibiotics and provide tetanus toxoid if immunization is not up to date

See Treatment and Medication for more detail.

Background

Blast injuries traditionally are divided into 4 categories: primary, secondary, tertiary, and quaternary (or miscellaneous) injuries. A patient may be injured by more than one of these mechanisms.[2, 3]

  • A primary blast injury is caused solely by the direct effect of blast overpressure on tissue. Air is easily compressible, unlike water. As a result, a primary blast injury almost always affects air-filled structures such as the lung, ear, and gastrointestinal (GI) tract.

  • A secondary blast injury is caused by flying objects that strike people.

  • A tertiary blast injury is a feature of high-energy explosions. This type of injury occurs when people fly through the air and strike other objects.

  • Miscellaneous or quaternary blast injuries encompass all other injuries caused by explosions, such as burns, crush injuries, and toxic inhalations. For example, the crash of two jet airplanes into the World Trade Center only created a relatively low-order pressure wave, but the resulting fire and building collapse killed thousands.

    Blast injuries. Estimated human tolerances for sin Blast injuries. Estimated human tolerances for single, sharp, rising blast waves. Courtesy of Bowen TE and Bellamy RF, eds, Emergency War Surgery. Washington, DC: United States Government Printing Office, 1988.

Explosions have the capability to cause multisystem, life-threatening injuries in single or multiple victims simultaneously. These types of events present complex triage, diagnostic, and management challenges for the health care provider. Explosions can produce classic injury patterns from blunt and penetrating mechanisms to several organ systems, but they can also result in unique injury patterns to specific organs including the lungs and the central nervous system. Understanding these crucial differences is critical to managing these situations.

The extent and pattern of injuries produced by an explosion are a direct result of several factors including the amount and composition of the explosive material (eg, the presence of shrapnel or loose material that can be propelled, radiological or biological contamination), the surrounding environment (eg, the presence of intervening protective barriers), the distance between the victim and the blast, the delivery method if a bomb is involved, and any other environmental hazards. No two events are identical, and the spectrum and extent of injuries produced varies widely.

Between 1991 and 2000, 93 terrorist attacks worldwide produced more than 30 casualties, with 885 of these incidents involving explosions. The 2005 London subway bombings, the 1995 bombing of the Murrah Federal Building in Oklahoma City, and the catastrophic explosions of aircraft into 3 buildings on September 11, 2001 in New York City and Washington DC reminded health care workers of the magnitude of injuries and death that can result from a blast mechanism. Internationally, explosive devices directed against both civilian and military targets are frequently used in war or acts of terrorism. Approximately 25,000 US and coalition forces and 100,000 Iraqis were estimated to have been injured or killed by explosions in the Global War on Terrorism as of early 2009.[2] Although the United States has been spared the majority of these events, the potential exists for use of explosive weapons in the United States in the future.

As the risk of terrorist bombings in the United States increases, emergency physicians and Emergency Medical Services (EMS) personnel should be especially concerned about radiation and/or chemical contamination of explosion victims. Careful observation for signs and symptoms of exposure to poisonous chemicals, screening for radiation contamination, and decontamination of patients as needed are important steps in the management of victims of nonaccidental explosions. In addition to deliberately set explosions, incidents also occur as a result of industrial accidents (eg, factory and mining operations, fuel transportation and storage, grain elevator explosions).

In many parts of the world, undetonated military incendiary devices such as land mines and hand grenades contaminate the sites of abandoned battlefields. Such devices cause significant numbers of civilian casualties years and even decades after local hostilities cease. During wartime, injuries arising from explosions frequently outnumber those from gunshots with many innocent civilians becoming victims.

Much of the challenge facing the care providers is the potential for the sudden creation of large numbers of patients who require extensive medical resources. This scenario can overwhelm local EMS and hospital resources. Emergency physicians must remain attentive to the possibility and consequences of blast injuries.

Once notified of a possible bombing or explosion, hospital-based physicians should consider immediately activating hospital disaster and contingency plans, including preparations to care for anywhere from a handful to hundreds of victims.

Pathophysiology

Blast injuries traditionally are divided into 4 categories: primary, secondary, tertiary, and quaternary (or miscellaneous) injuries. A patient may be injured by more than one of these mechanisms.[2, 3]

  • A primary blast injury is caused solely by the direct effect of blast overpressure on tissue. Air is easily compressible, unlike water. As a result, a primary blast injury almost always affects air-filled structures such as the lung, ear, and gastrointestinal (GI) tract.

  • A secondary blast injury is caused by flying objects that strike people.

  • A tertiary blast injury is a feature of high-energy explosions. This type of injury occurs when people fly through the air and strike other objects.

  • Miscellaneous or quaternary blast injuries encompass all other injuries caused by explosions, such as burns, crush injuries, and toxic inhalations. For example, the crash of two jet airplanes into the World Trade Center only created a relatively low-order pressure wave, but the resulting fire and building collapse killed thousands.

    Blast injuries. Estimated human tolerances for sin Blast injuries. Estimated human tolerances for single, sharp, rising blast waves. Courtesy of Bowen TE and Bellamy RF, eds, Emergency War Surgery. Washington, DC: United States Government Printing Office, 1988.

Frequency

United States

Incidence is sporadic and infrequent. Cases tend to be grouped several (up to hundreds) at a time and have the ability to temporarily overwhelm a local health care system.

International

Incidence is sporadic. Frequency depends on the political (terrorism, war) and economic (occupational health and safety priorities) stability of the region.

Mortality/Morbidity

Mortality rates vary widely between incidents. An analysis of 29 large terrorist bombing events between 1966 and 2002 showed 8,364 casualties, including 903 immediate deaths and 7,461 immediately surviving injured.[4] Immediate death/injury rates were higher for bombings involving structural collapse (25%) than for confined space (8%) and open air detonations (4%).

Unique patterns of injury are found in all bombing types. Injury is caused both by direct blast overpressure (primary blast injury) and by a variety of associated factors. Enclosed-space explosions, including those occurring in buses, and in-water explosions produce more primary blast injury. Blasts in ultra-confined spaces such as buses have the highest associated mortality.[5] Explosions leading to structure collapse produce more orthopedic injuries. Land mine injuries are associated with a high risk of below- and above-the-knee amputations. Fireworks-related injuries prompt an estimated 10,000-12,000 ED visits in the United States annually, with 20-25% involving either the eye or hand.

In a study of firework-related injuries treated in EDs in  the United States from 2000 to 2010, the rate was higher for children, with the highest rates being observed for 10-19 year olds (7.28 per 100,000 persons) and 0-9 year olds (5.45 per 100,000 persons). The injury rate was nearly 3 times higher for males than for females (4.48 vs. 1.57 per 100,000 persons). The most common injuries (26.7%) were burns of the wrist, hand, and finger, followed by contusion or superficial injuries to the eye (10.3%); open wounds of the wrist, hand, and finger (6.5%); and burns of the eye (4.6%).[6, 7]

Presence of tympanic membrane (TM) rupture indicates that a high-pressure wave (at least 40 kilopascal [kPa], 6 psi) was present and may correlate with more dangerous organ injury. Between 2% and 32% of patients injured by a blast will have TM rupture.[3] Theoretically, at an overpressure of 100 kPa (15 psi), the threshold for lung injury, the TM routinely ruptures; however, a recent Israeli case series of 640 civilian victims of terrorist bombings contradicts traditional beliefs about a clear correlation between the presence of TM injury and coincidence organ damage. Of 137 patients initially diagnosed as having isolated eardrum perforation who were well enough to be discharged, none later developed manifestations of pulmonary or intestinal blast injury. Furthermore, 18 patients with pulmonary blast injuries had no eardrum perforation.

Similarly, in a review of 167 patients who sustained blast exposure in Iraq, TM perforation was noted to be poorly sensitive as a biomarker for more serious primary blast injury. Only 50% of patients with serious PBI demonstrated TM rupture in this review.[8]

In a study of the relationship between tympanic membrane perforation (TMP) and severity of blast injury, TMP was more prevalent in patients with moderate and severe injuries than in mildly injured patients (53.3% vs. 13.6%). Patients with TMP more often needed surgery, ICU hospitalization, and need for transfer to a level I trauma center.[9]

Mild traumatic brain injury (mTBI) from primary blast forces may have greater post-concussive sequelae than mTBI from blunt forces. In a pilot study of 12 veterans with pure blast-force mTBI and 12 with pure blunt-force mTBI, both groups scored significantly lower than normal on the Rivermead Post-Concussion Questionnaire and the SF36-V Health Survey, but the blast-force group had lower scores than blunt-force group on the Paced Auditory Serial Addition Test. Significant correlations of test scores with hypometabolism in the right superior parietal region on PET scanning were seen only in the blast-force injury group.[10]

Severe head injury was the most common cause of death in a retrospective review of 71 casualties who reached medical treatment facilities alive but subsequently died from injuries sustained during combat operations in Afghanistan and Iraq. Thirty-three casualties (47%)  died from isolated head injuries, a further 13 (18%) had unsurvivable head injuries but not in isolation. Hemorrhage following severe lower limb trauma, often in conjunction with abdominal and pelvic injuries, was the cause of a further 15 deaths (21%).[11]

 

Presentation

History

 

If possible, determine what material caused the explosion. High-order explosives (HEs) undergo detonation, an almost instantaneous transformation of the original explosive material into gases occupying the same volume of space under extremely high pressure. These high-pressure gases rapidly expand, compress the surrounding medium, and produce a defining supersonic, overpressurization blast wave. Examples of HEs include materials such as TNT, ammonium nitrate fuel oil, dynamite, and C-4 "plastic" explosives. In general, only HE explosions produce severe primary blast injury.

Low-order explosives (LEs) are composed of propellants, such as black powder, and pyrotechnics, such as fireworks. LEs undergo deflagration rather than detonation and release energy relatively slowly compared with HEs. This results in a subsonic explosion lacking the overpressurization blast wave that characterizes HEs. Although LE explosions can be deadly, LE explosions very uncommonly cause the pulmonary and central nervous system injuries unique to primary blast injury.

If possible, determine the patient's location relative to the center of the explosion. An explosion that occurs in an enclosed space (including a building, a mine, or a relatively lightly constructed enclosed space such as a bus) or in water tends to cause more serious injury. Intensity of an explosion pressure wave declines with the cubed root of the distance from the explosion. A person 3 m (10 ft) from an explosion experiences 9 times more overpressure than a person 6 m (20 ft) away. Proximity of the person to the explosion is an important factor in a primary blast injury. Blast waves are reflected by solid surfaces; thus, a person standing next to a wall may suffer increased primary blast injury.

Because explosions often cause multiple casualties, anticipate activating the hospital or regional disaster plan.

Another ominous consideration is the tactic of setting dual explosions. The initial explosion is intended to injure civilians and to attract law enforcement and rescue personnel, followed by a delayed explosion designed to injure rescuers. Hospital disaster plans should include tight security at all hospital entrances in the event of a terrorist explosion in the community. All hospital personnel should be alert for unattended packages.

In addition to protecting hospital patients and staff, sealing entrances helps control the chaotic flow of patients and visitors.

Industrial accidents and terrorist explosions may be associated with the release of toxic and/or radioactive materials. The Federal Bureau of Investigation (FBI) is particularly concerned about the possibility that a terrorist could attach a radioactive substance (eg, a radiopharmaceutical or part of an old radiography machine) to a conventional explosive device, causing radiation contamination of the scene and casualties. In the 1993 attack on the World Trade Center, terrorists attached cyanide to a bomb placed in the underground parking garage. Fortunately, in that incident the cyanide was destroyed by the combustion. Physicians and EMS personnel must diligently search for evidence of radiation and/or chemical contamination in persons with blast injuries.

Question plant managers, fire department officials, EMS personnel, and law enforcement personnel about these possibilities.

EMS agencies should check for radiation contamination at the scene of a deliberately caused explosion. In addition, hospital personnel should screen persons who have been exposed to deliberate explosions for radioactivity with a Geiger counter or similar radiation dosimeter. Each hospital has a radiation safety officer (usually a radiology technician) who can assist with this task.

Physical

See the list below:

  • Examine lungs for evidence of pulmonary contusion and pneumothorax.

    • Assume that a patient's wheezing associated with a blast injury is from pulmonary contusion.

    • Other causes of wheezing in this setting may include inhalation of irritant gases or dusts, pulmonary edema from myocardial contusion, and adult respiratory distress syndrome (ARDS).

  • Many experts recommend obtaining a chest radiograph in the presence of isolated tympanic membrane (TM) rupture since this may indicate exposure to significant overpressure. In a large series of victims of terrorist bombings, mostly involving closed spaces, 22% of patients with eardrum perforation had other significant injuries.

    • However, a patient with isolated TM perforation, but no other immediately identified injuries, does not automatically require an extended period of observation. In the above study, none of the 137 patients initially identified as having isolated TM rupture and well enough to be discharged developed later manifestation of pulmonary or intestinal blast injury.

    • Intact TMs do not imply the absence of serious injury, especially if the patient was wearing some type of hearing protection as is common in certain types of military or law enforcement operations.

  • Abdominal injuries from explosions may be occult, and serial examinations are often required.

    • A recent large Israeli case series found that abdominal injuries occurred only as a result of massive trauma. This finding may be the result of selection bias, as all the explosions in their series occurred in open air. Air is a poor conductor of blast-wave energy, thus those who were subjected to enough energy to damage abdominal organs probably were situated near the explosive devices.

    • Other authors have reported occult injuries to both solid and hollow abdominal organs in people injured by closed-space explosions and blast injuries occurring in water.

Causes

Primary blast injury

Primary blast injury (PBI) is organ and tissue damage caused solely by the blast wave associated with HEs.

Blast injuries. Idealized graph of a blast pressur Blast injuries. Idealized graph of a blast pressure wave over time. Courtesy of Bowen TE and Bellamy RF, eds, Emergency War Surgery. Washington, DC: United States Government Printing Office, 1988.

The leading edge of a blast wave is called the blast front. When a blast front reaches a victim, it causes an enormous, almost instantaneous rise in ambient pressure. For example, C4 explosions can create initial pressures of over 4 million pounds per square inch (30GPa).

Because explosive gases continue to expand from their point of origin, a longer negative underpressure (relative vacuum) follows the peak positive overpressure. Both the positive overpressure and the negative underpressure are capable of causing significant PBI.

Since air is easily compressible by pressure while water is not, gas-containing organs, especially the lungs, bowel, and middle ear, are most susceptible to PBI.

Pulmonary barotrauma is the most common fatal primary blast injury. This includes pulmonary contusion, systemic air embolism, and free radical–associated injuries such as thrombosis, lipoxygenation, and disseminated intravascular coagulation (DIC). ARDS may be a result of direct lung injury or of shock from other body injuries.

Thoracic PBI produces a unique cardiovascular response, observed nowhere else in medicine, that which is sufficient to cause death in the absence of any demonstrable physical injury. The immediate cardiovascular response to pulmonary blast injury is a decrease in heart rate, stroke volume, and cardiac index. The normal reflex increase in systemic vascular resistance does not occur, so blood pressure falls. This effect occurs within seconds. If this response is not fatal, recovery usually occurs within 15 minutes to 3 hours. However, even nonlethal PBI can impair pulmonary performance for hours to days.

Thoracic PBI may possibly result in pericardial tamponade even in the absence of penetrating trauma (secondary blast injury).[12]

Acute gas embolism (AGE), a form of pulmonary barotrauma, requires special attention. Air emboli most commonly occlude blood vessels in the brain or spinal cord. Resulting neurologic symptoms must be differentiated from the direct effect of trauma.

Intestinal barotrauma is more common with underwater than air blast injuries. Although the colon usually is affected most, any portion of the GI tract may be injured.

The ear is the organ most susceptible to primary blast injury. Acoustic barotrauma commonly consists of TM rupture. Hemotympanum without perforation also has been reported. Ossicle fracture or dislocation may occur with very high-energy explosions.

PBI of the brain may be associated with impaired cerebral vascular function including compensatory mechanisms for traumatic brain injury. Reactive oxygen species, including superoxide anion radical and nitric oxide, are likely major contributors.[13]

Secondary blast injury

Secondary blast injuries (SBIs) are caused by flying objects striking individuals.

This mechanism is responsible for the majority of casualties in many explosions. Penetrating thoracic trauma, including lacerations of the heart and great vessels, is a common cause of death in the setting of SBIs. For example, the glass facade of the Alfred P. Murrah Federal Building in Oklahoma City shattered into thousands of heavy glass chunks that were propelled through occupied areas of the building with devastating results.[14, 15] During the 1998 terrorist bombing of the US Embassy in Nairobi, flying glass wounded people up to 2 km away.

Military explosive casings (eg, hand grenades) are specifically designed to fragment and to maximize damage from flying debris (shrapnel).

Civilian terrorist bombers (eg, Olympic Park in Atlanta) often deliberately place screws or other small metal objects around their weapons to increase secondary blast injuries.

Tertiary blast injury

Tertiary blast injuries are caused by individuals flying through the air and striking other objects, generally from high-energy explosions.

Unless the explosion is of extremely high energy or focused in some way (eg, through a door or hatch), a person with tertiary blast injury usually is very close to the explosion source.

Together with SBIs, this category accounted for most of the pediatric casualties in the Oklahoma City bombing. A high incidence of skull fractures (including 17 children with open brain injuries) and long-bone injuries including traumatic amputations occurred.[16]

Quaternary blast injury

Miscellaneous blast-related injuries, sometimes termed quaternary blast injury, include burns (chemical or thermal); injury from falling objects; crush injuries from collapsed structures and displaced heavy objects; falls resulting from the explosion; and toxic dust, gas, or radiation exposure. Acute methemoglobinemia has been reported after nitroglycerine transcutaneous absorption resulting from a bomb explosion.[17]

 

DDx

 

Workup

Laboratory Studies

Judicious use of the laboratory is essential for accurate diagnosis in the mass-casualty situation. Do not overwhelm the laboratory with screening or protocol laboratory tests of little clinical benefit.

  • Most patients injured by significant explosions should have a screening urinalysis.

  • If the explosion occurred in an enclosed space or was accompanied by fire, test carboxyhemoglobin (HbCO) and electrolytes to assess acid/base status.

    • Pulse oximetry readings may be misleading in cases of CO poisoning. When in doubt, apply 100% oxygen by tight-fitting face mask until CO levels can be measured.

    • Exposure to cyanide (CN), a product of incomplete combustion of plastics, is difficult to measure directly. CN exposure often accompanies CO poisoning. Consider CN poisoning in patients exposed to combustion in an enclosed space who have an anion gap metabolic acidosis (see the Anion Gap calculator). Treatment for CN poisoning should be started for significantly ill patients while awaiting confirmatory test results. Sodium thiosulfate or hydroxocobalamin are safe and appropriate empiric therapies.

  • Victims of major trauma should have baseline hemoglobin determinations, crossmatching for potential blood transfusion, and screening for DIC.

    • If significant crush injury, compartment syndrome, or severe burns have occurred, emergency physicians should be attentive to the possibility of rhabdomyolysis with resulting hyperkalemia and myoglobinuric renal failure.

    • Useful tests for DIC include the following:

      • Protime

      • Activated partial thromboplastin time (aPTT)

      • Thrombin time

      • Fibrinogen

      • Fibrin split products

      • D-dimer levels

      • Serial CBC determinations, to include platelet counts

    • Patients with burns from military white phosphorous (WP) munitions are at risk for hypocalcemia and hyperphosphatemia; follow serial levels of these ions. WP is a metal that ignites on contact with air, creating intense heat and releasing phosphorous pentoxide, a severe pulmonary irritant. WP is a widely used component of military munitions, including hand grenades.

Imaging Studies

Perform chest radiography in patients who have been exposed to high overpressure and are therefore at high risk for primary blast injury. This group of patients may include all patients with TM rupture from blast injury. Chest radiographs should be performed on all patients who exhibit respiratory symptoms, have abnormal findings on auscultation, or have visible external signs of thoracic trauma.

If significant abdominal pain is present, consider an immediate abdominal radiographic series (flat and upright films) or abdominal CT to detect pneumoperitoneum from enteric rupture. The Focused Abdominal Sonography for Trauma (FAST) examination is a potentially useful tool for rapidly screening patients, especially in the setting of multiple seriously injured victims. A positive FAST examination in an unstable patient is an indication for surgical exploration of the abdomen in the operating room. In stable patients, a positive FAST examination can facilitate prioritization for CT imaging. A negative FAST examination is unreliable in the setting of penetrating trauma to the abdomen, flank, buttocks, or back, and it should be followed up with CT examination of the abdomen and pelvis. Ultrasonography can rapidly rule out the presence of pericardial tamponade.

No practical, sensitive test exists for intestinal hematoma. The diagnosis is often missed even when performing the best available test — abdominal CT. Because intestinal hematoma can take 12-36 hours to develop, symptoms such as increased pain or vomiting should determine decisions about testing.

Other Tests

If there is any question of radiation or chemical contamination, arrange to test and decontaminate patients and equipment.

  • Most fire departments' hazardous materials teams have the training and equipment to perform this task.

  • Notify the hospital's radiation safety officer (often the chief technician for the radiology department's nuclear medicine section) for assistance screening victims for radiation contamination. Contact hospital public relations to work with the press.

 

Treatment

Prehospital Care

EMS personnel should attempt to determine and report any information regarding the nature and size of the explosion; the time of occurrence; the proximity of the victim to the epicenter of the blast; victim displacement by the blast wind if any; the presence of secondary fires, smoke, dust, or chemical or radioactive contamination; and history of entrapment in collapsed structures. EMS personnel are responsible for activating appropriate disaster and/or hazardous material responses as early as possible.

  • Analysis of blast incidents indicates that "upside-down" triage is common; less injured patients typically arrive at the hospital, via ambulance or private vehicle, before the most severely injured victims.

  • Screening for radioactive contamination with a hand-held Geiger counter is a prudent precaution for any explosion that may involve radioactive material, including any explosion that may have been deliberately set. If radioactive material is detected, decontamination of personnel and equipment as well as notification of the receiving hospital is required. The Radiation Emergency Action Center and Training Site (REAC/TS) provides advice and assistance; their 24-hour emergency telephone number is +1 (865) 576-1005undefined.

  • Significant extremity trauma and associated death from exsanguination is a major cause of preventable death. EMS personnel should rapidly identify patients with life-threatening external hemorrhage and control bleeding. Early use of tourniquets may be life-saving, especially in the setting of multiple seriously injured casualties.

  • High-flow oxygen should be administered to all patients with respiratory distress, abnormal findings on auscultation, and evidence of significant thoracic trauma.

  • EMS personnel should avoid administration of large quantities of intravenous fluid in patients with a high suspicion of ongoing internal hemorrhage. Judicious fluid boluses may be required if patients exhibit signs and symptoms of inadequate perfusion, such as deteriorating mental status, in this setting. Recent experiences on the battlefield suggest that Hextend is the preferred resuscitation fluid for the prehospital setting.

  • EMS personnel should initiate measures to reduce heat loss and prevent hypothermia in the trauma patient since this condition is associated with increased mortality.

  • In cases of life-threatening extremity trauma secondary to blast injuries, early use of tourniquets may prove lifesaving. In a study comparing combat application tourniquet (CAT) to the newer emergency and military tourniquet (EMT) pneumatic tourniquet, the CAT tourniquet proved ineffective in controlling arterial blood flow when applied at mid-thigh level while EMT was successful in a significantly larger number of patients.[18]

The FDA has approved an expandable, multi-sponge, temporary wound dressing (XSTAT) to control bleeding from certain types of wounds received in battle. The dressing, which can be used for up to four hours, consists of 3 syringe-style applicators with 92 compressed cellulose sponges that have an absorbent coating. These sponges expand and swell to fill the wound cavity, creating a temporary physical barrier to blood flow. Each tablet-shaped sponge measures 9.8 millimeters in diameter and 4 to 5 millimeters in height, and can absorb 3 milliliters of blood or body fluid. This dressing is currently approved for military use only.[19]

 

Emergency Department Care

 

Examine the lungs, abdomen, and TMs of all patients exposed to a significant explosion.

Penetrating wounds (secondary blast injury), blunt trauma (tertiary/secondary blast injury), and burns receive standard treatment.

Shrapnel wounds (secondary blast injury) are treated as low-velocity gunshot wounds.

Hemodynamically unstable patients with significant trauma may benefit from early use of packed red blood cells (PRBC) and fresh frozen plasma (FFP) in a 1:1 ratio, as well as platelets. Recent battlefield experience suggests a benefit to the early use of fresh whole blood if available. Additionally, cryoprecipitate and recombinant factor VIIa should be considered in the severe trauma patient, especially in the setting of massive transfusion requirements. One review of 3 mass casualty incidents following explosive events in Iraq suggested that this resuscitation strategy resulted in the transfusion of an average 3.5 units of PRBC and 3.8 units of plasma, as well as a mortality rate of 8%.[20]

The prevention of hypoxia and hypotension are critical in patients with traumatic brain injury to prevent significant increases in mortality.[13]

Because pulmonary contusion tends to evolve over several hours, a period of observation and repeat radiography may be necessary if indicated. Definitive airway management and ventilatory support may be required.

If abdominal pain persists or vomiting develops, consider admitting the patient for observation. Intestinal hematoma may be difficult to detect in the ED.

White phosphorus (WP) burns require unique management. Initial management of WP-contaminated burns consists of copious lavage of the area, removing identifiable particles (which should be placed in water to prevent further combustion), and covering the area with saline-soaked gauze to prevent further combustion. Use of a Wood lamp in a darkened resuscitation suite or operating room may help identify WP particles in the wound.

Definitive treatment consists of a rinse using 1% copper sulfate (CuSO4) solution and removing the WP particles. Copper sulfate combines with phosphorous particles to create a blue-black cupric phosphide coating. This impedes further WP combustion and makes particles easier to find. Rinse the contaminated burn with copper sulfate solution, remove WP particles, and then use copious saline lavage to rinse off the copper sulfate. Never apply copper sulfate as a dressing. Excess copper sulfate absorption can cause intravascular hemolysis and renal failure.

WP injury can lead to hypokalemia and hyperphosphatemia with ECG changes, cardiac arrhythmias, and death. Place the patient on a cardiac monitor and closely track serum calcium levels. Intravenous (IV) calcium may be required. Moistened face masks and good ventilation help protect patients and medical personnel from the pulmonary effects of phosphorous pentoxide gas. Naturally, avoid the use of flammable anesthetic agents and excessive oxygen around WP.

Consultations

Consult a trauma surgeon, otolaryngologist, pulmonary medicine specialist, critical care specialist, orthopedic surgeon, plastic surgeon, urologist, and toxicologist, as required.

 

Medication

Medication Summary

Research into the pathophysiology of primary blast injury (PBI) continues. On a cellular level, shock waves produce an inflammatory response. Interleukin 8 is released, causing mobilization of polymorphonuclear leukocytes (PMNs) into the systemic circulation. The release of proinflammatory cytokines induces the expression of the CD11b receptor complex on the PMN surface, leading to adhesion at the site of injury. Select free-radical scavengers and inhibitors of inflammatory pathways are promising in phase I animal trials. In addition, blast injury to the lungs causes levels of inducible nitric oxygen synthase (iNOS) to increase in the brain, causing brain injury. The iNOS inhibitor aminoguanidine appears to be effective when administered to mice either before or 1 hour after the blast, but human data are lacking.

Although animal models suggest that bradycardia and hypotension observed in primary blast injury may be vagally mediated, it would be premature to recommend atropine at this time.

Broad-spectrum prophylactic antibiotics should be considered for patients with open wounds from blasts. Tetanus immunization status should be confirmed, and tetanus toxoid should be provided as required.

Use of copper sulfate solution for management of burns contaminated with the military munition WP is described in Emergency Department Care.

 

Follow-up

Further Outpatient Care

As symptoms of pulmonary contusion and intestinal hematoma may take 12-48 hours to develop, instruct all discharged patients to return for reevaluation if they develop breathing problems, increasing abdominal pain, or vomiting.

Outpatient treatments for blast-related lacerations, burns, contusions, fractures, and other injuries are the same as for these injuries from other causes.

Tympanic membrane (TM) rupture by itself does not require specific treatment or hospitalization. Patients should be instructed not to put anything in the affected ear and should be referred to ENT for follow-up care. Remember that neomycin (a component of otic solutions and suspensions) is ototoxic and theoretically contraindicated in cases of TM perforation.

Most cases of TM perforation heal spontaneously; however, complications such as ossicle disruption, cholesteatoma formation, and development of perilymphatic fistulae are possible. About one third of patients with TM perforation have permanent hearing loss.

Exposure to blasts may induce vestibular disorders that progress over time. Referral to neurology and ENT should be considered for follow-up care.[21] Physical therapy referral may be required for vestibular rehabilitation.[22]

Exposure to blasts may result in mild traumatic brain injury (mTBI) and predispose to posttraumatic stress disorder (PTSD).[23] Patients with residual symptoms should be referred to neurologists and mental health specialists as required. Although insufficient data exist to make a definitive recommendation, hyperbaric oxygen (HBO) may be of some benefit in the treatment of blast-related postconcussive symptoms.[24]

Further Inpatient Care

A high rate of ICU admission and ventilator requirement should be anticipated. In a review of 3 mass casualty incidents, approximately 50% of surgical patients with injuries resulting from blasts required each of these.[20]  Limited data prevent establishing the optimal duration of observation.

Consider the following guidelines:

  • Persons who are exposed to open-space explosions and who have no apparent significant injury and normal vital signs and unremarkable lung and abdominal examinations generally can be discharged after 4 hours of observation. Return instructions should include shortness of breath, abdominal pain, vomiting, or other symptoms occur.
  • Persons exposed to significant closed-space explosions, in-water explosions, and those who incur tympanic membrane (TM) rupture are at higher risk of delayed complications. All these patients should have chest radiography, and selected patients should have imaging of other organs. Even if no injury is identified, these patients should receive more intensive observation over a longer period. Motivated, reliable, and completely asymptomatic patients may be sent home after 4 hours of observation.
  • Admit to the hospital all patients with significant burns, suspected air embolism, radiation or WP contamination, abnormal vital signs, abnormal lung examination findings, clinical or radiographic evidence of pulmonary contusion or pneumothorax, abdominal pain, vomiting, evidence of renal contusion/hypoxia, or penetrating injuries to the thorax, abdomen, neck, or cranial cavity.

For patients thought to have arterial gas embolism (AGE) or cerebral AGE:

  • Positive pressure ventilation (PPV) and positive end expiratory pressures (PEEP) should be avoided whenever possible in the setting of pulmonary blast injury due to the risk of pulmonary alveolar rupture and subsequent formation of air emboli. However, mechanical ventilation often cannot be avoided. Due to the nonhomogeneous pulmonary compliance that characterizes the blast lung, localized overinflation of the more compliant lung segments occurs when high ventilatory pressures are used. Whenever possible, reduce the tidal volume to limit peak inspiratory pressure (PIP) and minimize ventilator-induced lung barotrauma injury. If necessary, consider permissive hypercapnia ventilation: reduce the tidal volume to maintain PIP less than 35-40 cm H 2 O; make no attempts to control PaCO 2 levels until the arterial pH falls below 7.20. When respiratory acidosis becomes too severe, increase the respiratory rate until the arterial pH rises above 7.25.
  • Patients thought to have AGE require recompression treatment. Place patients on 100% oxygen by tight-fitting face mask and, if possible, place them in the left lateral recumbent position to minimize the risk of travel of the air embolism out of the heart. Trendelenburg (head down) position is no longer recommended. If the side of the lung responsible for the AGE can be identified, unilateral lung ventilation may prevent further introduction of air into the vascular system during positive pressure ventilation.
  • In the setting of acute mental status, cerebral AGE should be considered as well as other causes of symptoms (eg, traumatic CNS injury).
  • Hyperbaric oxygen (HBO) treatment is the definitive procedure for AGE and cerebral AGE. Transfer of the patient to a facility with HBO therapy may be required.
  • Research suggests that aspirin is helpful in AGE. Aspirin may reduce inflammation-mediated injury in pulmonary barotrauma as well. However, it may be unwise to give an antiplatelet agent to a patient with acute trauma.

Transfer

Patients with significant burns should be transferred to a burn center if the initial receiving hospital does not have adequate facilities.

Consider transfer to a Level 1 trauma center for severely injured patients.

Consider transfer to a facility with hyperbaric chamber for patients who develop suspected AGE secondary to PBI of the lung.

Deterrence/Prevention

Garments designed to protect against both primary blast injuries (PBIs) and secondary blast injuries (SBIs) have proven very effective in the military setting. However, except for use by bomb squad technicians and tactical law enforcement personnel, these garments have little applicability in the civilian setting.

Prehospital personnel should be cognizant of the possibility of a secondary device designed to target rescuers when responding to the scene of a suspected intentional bombing. Hospitals similarly may be attractive targets to terrorists and should ensure heightened security for the facility in the event of a bombing.

Complications

Various sequelae of traumatic injuries may occur.

Crush syndrome and acute renal failure may occur in the setting of patients rescued from collapsed structures.

Increasing extremity pain after an explosion should raise the suspicion of developing compartment syndrome.