Blast injury

Infobox_Disease
Name = Blast injury


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eMedicineSubj = emerg
eMedicineTopic = 63
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A blast injury is the result of physical trauma sustained in an explosion. Blast injuries are occur with the detonation of high-order explosives, explosives that produce a supersonic over-pressurization shock wave, as well as low order explosives which produce a subsonic explosion with no over-pressurization wave. These injuries are compounded when the explosion takes place in a confined space.

A blast wave generated by an explosion starts with a single pulse of increased air pressure, lasting a few milliseconds. The negative pressure (suction) of the blast wave follows immediately after the positive wave. The duration of the blast wave, i.e., the time an object in the path of the shock wave is subjected to the pressure effects, depends on the type of explosive and the distance from the point of detonation. The blast wave progresses from the source of explosion as a sphere of compressed and rapidly expanding gases, which displaces an equal volume of air at a very high velocity. The velocity of the blast wave in air may be extremely high, depending on the type and amount of the explosive used. Indeed, while a hurricane-force wind (approximately 200 km/h) exerts only 0.25 PSI overpressure (i.e. 1.72 kPa), a lethal blast-induced overpressure of 100 PSI (i.e. 690 kPa) travels with a velocity of approximately 1500 mph (i.e. 2414 km/h). An individual in the path of an explosion will be subjected not only to excess barometric pressure, but to pressure from the high-velocity wind traveling directly behind the shock front of the Blast wave. The magnitude of damage due the Blast wave is dependent on: 1) the peak of the initial positive pressure wave (bearing in mind that an overpressure of 60-80 PSI or 414-552 kPa is considered potentially lethal); 2) the duration of the overpressure; 3) the medium in which it explodes; 4) the distance from the incident blast wave; and 5) the degree of focusing due to a confined area or walls. For example, explosions near or within hard solid surfaces become amplified two to nine times due to shock wave reflection. As a result, individuals between the blast and a building generally suffer two to three times the degree of injury compared to those in open spaces.

cite book |last= Marks |first= Michael E. |title= The Emergency Responder's Guide to Terrorism |publisher= Red Hat Publishing Co., Inc. |year= 2002 |pages= 30-32 |isbn= 1-932235-00-0 ]

Classification

Blast injuries are divided into four classes: primary, secondary, tertiary, and quaternary.

Primary injuries are due to high-order explosive over-pressurization shock wave as it moves through the body targeting gas-containing organs such as the ear, lungs, and gastrointestinal tract) or those containing structures with different specific weights. In general, primary blast injuries are characterized by the absence of external injuries; thus internal injuries are frequently unrecognized and their severity underestimated. According to the latest experimental results, the extent and types of primary blast-induced injuries depend not only on the peak of the overpressure, but also other parameters such as number of overpressure peaks, time-lag between overpressure peaks, characteristics of the shear fronts between overpressure peaks, frequency resonance, and electromagnetic pulse, among others. There is general agreement that spalling, implosion, inertia, and pressure differentials are the main mechanisms involved in the pathogenesis of primary blast injuries. Thus, the majority of prior research focused on the mechanisms of blast injuries within gas-containing organs/organ systems such as the lungs, while primary blast-induced brain injury has remained underestimated. "Blast lung" refers to severe pulmonary contusion, bleeding or edema with damage to alveoli and blood vessels, or a combination of these.cite journal |author=Sasser SM, Sattin RW, Hunt RC, Krohmer J |title=Blast lung injury |journal=Prehosp Emerg Care |volume=10 |issue=2 |pages=165–72 |year=2006 |pmid=16531371 |doi=10.1080/10903120500540912 |url=] It is the most common cause of death among people who initially survive an explosion.cite journal |author=Born CT |title=Blast trauma: The fourth weapon of mass destruction |journal=Scandanavian Journal of Surgery |volume=94 |issue=4 |pages=279–285 |year=2005 |pmid=16425623 |doi= |url=] Secondary injuries are due to bomb fragments and other objects propelled by the explosion. These injuries may affect any part of the body and sometimes result in penetrating trauma with visible hemorrhage (bleeding). At times the propelled object may become embedded in the body, obstructing the loss of blood to the outside. However, there may be extensive blood loss within the body cavities. Shrapnel wounds may be lethal and therefore many anti-personnel bombs are designed to generate shrapnel and fragments. Tertiary injuries result when a person becomes a missile and is thrown against other objects. The injuries sustained are then similar to those that are sustained by blunt trauma, including bone fractures and coup contre-coup injuries. Quaternary injuries are all other injuries not included in the first three classes. These include burns, crushing injuries and respiratory injuries.

Neurotrauma

Blast injuries can cause hidden brain damage and potential neurological consequences. Its complex clinical syndrome is caused by the combination of all blast effects, i.e., primary, secondary, tertiary and quaternary blast mechanisms. It is noteworthy that blast injuries usually manifest in a form of poly-trauma, i.e. injury involving multiple organs or organ systems. Bleeding from injured organs such as lungs or bowel causes a lack of oxygen in all vital organs, including the brain. Damage of the lungs reduces the surface for oxygen uptake from the air, reducing the amount of the oxygen delivered to the brain. Tissue destruction initiates the synthesis and release of hormones or mediators into the blood which, when delivered to the brain, change its function. Irritation of the nerve endings in injured peripheral tissue and/or organs also significantly contributes to blast-induced neurotrauma.

Individuals exposed to blast frequently manifest loss of memory for events before and after explosion, confusion, headache, impaired sense of reality, and reduced decision-making ability. Patients with brain injuries acquired in explosions often develop sudden, unexpected brain edema and cerebral vasospasm despite continuous monitoring; however, the first symptoms of blast-induced neurotrauma (BINT) are latent, occurring months or sometimes years after the initial event.fact|date=June 2008 The broad variety of symptoms includes weight loss, hormonal imbalance, chronic fatigue, headache, and problems in memory, speech and balance. These changes are often debilitating, interfering with daily activities. Because BINT in blast victims is underestimated, valuable time is often lost for preventive therapy and/or timely rehabilitation.fact|date=June 2008

ee also

*Battlefield medicine
*Bomb
*Explosive
*Suicide bombing
*Chest trauma

External links

* [http://www.bt.cdc.gov/masscasualties/surgecapacity.asp "In a Moment’s Notice: Surge Capacity in Terrorist Bombings"] US Centers for Disease Control and Prevention
* [http://www.bt.cdc.gov/masscasualties/bombings_injurycare.asp "Bombings: Injury Patterns and Care"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjuryfacts.asp "Blast Injuries: Fact Sheets for Professionals"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastessentials.asp "Blast Injuries: Essential Facts"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjury-prehospital.asp "Injury Care: Prehospital"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastlunginjury_prehospital.asp "Lung Injury: Prehospital Care"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastlunginjury.asp "Lung Injury"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjury-radio.asp "Radiological Diagnosis"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjury-crush.asp "Crush Injury and Crush Syndrome"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjury-postexposure.asp "Post Exposure Prophylaxis for Bloodborne Pathogens"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjury-abdominal.asp "Abdominal Injuries"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjury-extremity.asp "Extremity Injuries"] US Centers for Disease Control and Prevention
* [http://www.bt.cdc.gov/masscasualties/blastinjury-ear.asp "Ear Injuries"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/Blastinjury-eye.asp "Eye Injuries"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjury-thermal.asp "Thermal Injuries"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjury-pediatraics.asp "Pediatrics"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjury-olderadults.asp "Older Adults"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjury-bombings-mentalhealth.asp "Bombings and Mental Health"] US Centers for Disease Control and Prevention

* [http://www.bt.cdc.gov/masscasualties/blastinjury-RDD.asp "Radiological Dispersal Devices and Radiation Injury"] US Centers for Disease Control and Prevention

References

* [http://www.bt.cdc.gov/masstrauma/explosions.asp#blast Explosions and Blast Injuries: A Primer for Clinicians] from the CDC
* McSwain N. E. & Frame S., 2003, PHTLS Basic and Advanced Prehospital Trauma Life Support, 5th ed., Mosby, St. Louis
*Benzinger, T. (1950). Physiological effects of blast in air and water. In German Aviation Medicine, World War II (Vol. 2, pp. 1225-1229). Washington DC: Department of the Air Force.
*Cernak, I., Savic, J., Ignjatovic, D., & Jevtic, M. (1999). Blast injury from explosive munitions. J Trauma, 47(1), 96-103; discussion 103-104.
*Cernak, I., Savic, J., Zunic, G., Pejnovic, N., Jovanikic, O., & Stepic, V. (1999). Recognizing, scoring, and predicting blast injuries. World J Surg, 23(1), 44-53.
*Cernak, I., Savic, V. J., Kotur, J., Prokic, V., Veljovic, M., & Grbovic, D. (2000). Characterization of plasma magnesium concentration and oxidative stress following graded traumatic brain injury in humans. J Neurotrauma, 17(1), 53-68.
*Cernak, I., Savic, V. J., Lazarov, A., Joksimovic, M., & Markovic, S. (1999). Neuroendocrine responses following graded traumatic brain injury in male adults. Brain Inj, 13(12), 1005-1015.
*Cernak, I., Wang, Z., Jiang, J., Bian, X., & Savic, J. (2001a). Cognitive deficits following blast injury-induced neurotrauma: possible involvement of nitric oxide. Brain Inj, 15(7), 593-612.
*Cernak, I., Wang, Z., Jiang, J., Bian, X., & Savic, J. (2001b). Ultrastructural and functional characteristics of blast injury-induced neurotrauma. J Trauma, 50(4), 695-706.
*Chiffelle, T. L. (1966). Pathology of direct air-blast injury. In Technical Progress Report DA-49-146-XY-055. Washington DC: Defense Atomic Support Agency, Department of Defense.
*Clemedson, C. J. (1956). Blast injury. Physiol. Rev., 36, 336-354.
*Dedushkin, V. S., Kosachev, I. D., Tkachenko, S. S., & Shapovalov, V. M. (1992). [Rendering medical care and the volume of the treatment of victims with blast injuries (a review of the literature)] . Voen Med Zh.(1), 13-18.
*Owen-Smith, M. S. (1981). Explosive blast injury. Med Bull US Army Eur, 38(7/8), 36-43.
*Phillips, Y. Y., & Zajtchuk, J. T. (1989). Blast injuries of the ear in military operations. Ann Otol Rhinol Laryngol Suppl., 140, 3-4.
*Rice, D., & Heck, J. (2000). Terrorist bombings: Ballistics, patterns of blast injury and tactical emergency care. The Tactical Edge Journal, Summer, 53-55.
*Rossle, R. (1950). Pathology of blast effects. In German Aviation Medicine, World War II (Vol. 2, pp. 1260-1273). Washington DC: Department of the Air Force.
*Saljo, A., Bao, F., Haglid, K. G., & Hansson, H. A. (2000). Blast exposure causes redistribution of phosphorylated neurofilament subunits in neurons of the adult rat brain. J Neurotrauma., 17(8), 719-726.