|Year : 2014 | Volume
| Issue : 2 | Page : 85-88
Sunkara Venkateswara Kumar
Professor, Department of Surgery, Principal, Andhra Medical College and Assoc. King George Hospital, Visakhapatnam, Andhra Pradesh, India
|Date of Web Publication||11-Aug-2014|
Sunkara Venkateswara Kumar
Professor, Department of Surgery, Principal, Andhra Medical College and Assoc. King George Hospital, Visakhapatnam - 530002, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Blast injuries due to explosions remain the leading cause of death and injury to military personnel. Explosive devices have also been a preferred weapon of terrorists as they are cheap to manufacture and can cause lots of casualties. Multiple system involvement including burns to partial to full traumatic amputations can even tax the advanced trauma centers. Death is often the result of combined blast, ballistic and thermal effect injuries (Multi dimensional injuries).
Keywords: Injuries, multiple system involvement, small entry wounds
|How to cite this article:|
Kumar SV. Blast injuries. J Mahatma Gandhi Inst Med Sci 2014;19:85-8
| Introduction|| |
Blast injuries due to explosions are the primary cause of death and injury to combatants and civilian population. Blast injuries primarily result in burns and amputations. The management of blast injury casualties is complex due to presentation in mass-casualty events, the presence of multiple penetrating wounds and the possibility of co-existing primary, secondary, tertiary and/or quaternary injuries. Blast exposure has the potential to derange multiple body systems and each having implication for early treatment [Figure 1].
| Recent Blasts in and Around Visakhapatnam City, Andhra Pradesh, India|| |
- Hindustan Petroleum Corporation Limited, Visakhapatnam refinery blast on August 23 rd 2013 resulted in death of 29 personnel: The accident occurred due to sparks that originated from welding near a pipeline, which lead to collapse of cooling towers. Majority of the victims suffered burn injuries. Seven of the victims were airlifted to National Burns Center, Mumbai, for better treatment. This is a classic example of quaternary injuries and also partly tertiary injuries (structural collapse).
- Visakhapatnam Steel Plant blast on June 13 th 2012 led to death of 23 personnel: Explosions in the oxygen unit of the plant was the cause for the accident. Most of the victims suffered 80-90% burn injuries, which was the major cause for mortality. This is again another classical example of quaternary injuries.
- National Thermal Power Corporation, Visakhapatnam plant blast on July 1 st 2012 Scores (large number) injured: This mishap occurred due to explosion in conveyor belt leading to multiple injuries.
The physics behind an explosion
The blast wave that contains most of the energy, is released by the explosion. About 2000-6000°C temperature is attained within few milliseconds. Due to the blast, gas molecules become heated and highly pressurized. The heated gas expands in to the surrounding air at speeds higher than light, compressing air and producing shock wave. 
Injuries from blasts are classified into primary (due to direct effect of blast), secondary (due to projectiles from blast), tertiary (due to structural collapse, violent displacement and entrapment) and quaternary injuries (due to burns, inhalation injuries and exacerbation of pre-existing medical conditions such as chronic obstructive pulmonary disease [COPD], coronary artery disease [CAD] etc.). The blast waves destroy living tissues by spalling, implosion, acceleration-deceleration and pressure differential mechanisms. 
Primary blast injuries
The pressure differentials upon tissues of heterogeneous densities, i.e., air filled organs are mainly responsible for these primary injuries. The tympanic membrane (TM) is known to be the first organ to get affected by the blast and as little as 5 psi (Pounds per square inch) of pressure is enough to cause damage. An intact TM doesn't indicate the lack of pulmonary injury.  In blast lung, alveoli become flooded with fluid and cellular debris. Mild traumatic brain injury (mTBI) results from free radical release and neuronal cell death.
Secondary blast injuries (SB)
These are more common than primary injuries and result from objects that have been energized by the explosion to become projectiles. These SB injuries are the real killers of explosions. Injuries sustained to head, neck or chest may carry high mortality. Close proximity injuries can result in decapitation, dismemberment and extreme tissue devastations.
If the local pressure exceeds 100 psi, projectiles can cause 20-25 times far greater degree of soft-tissue derangement and cavitation larger than the size of fragment itself.
Tertiary blast injuries
Structural collapse, violent displacement and entrapment cause tertiary injuries. This mechanism has the potential to kill a large number of victims at the scene.
The thermal effects of blast exposure and other environmental factors are responsible for these injuries. These comprise of burns, inhalation injuries and exacerbation of pre-existing medical conditions like COPD, CAD etc.
| General Guidelines of Management|| |
The management of these complex multiple wounds is challenging with triage and scene safety being of utmost importance. Penetrating blast injuries to the head, neck, face and chest cause most fatalities after an explosion. A thorough clinical examination is an important part of initial assessment.
The first priority is securing the airway, once the patient is transferred to a safe location. To minimize significant blood loss tourniquets should be applied to the extremity injured, as first resort but not as last resort. Treatment of hemorrhagic shock is a central theme in those who do not succumb immediately. In patients requiring massive transfusions a 1:1 ratio of packed red blood cell units to plasma units is achieved. Early pain control with morphine, after excluding head injury, also helps to decrease the incidence of post-traumatic stress disorders. Since the TM is most sensitive to the blast pressure wave, the absence of rupture would greatly decrease the risk of blast injury to lung, bowel or brain. If TM rupture is present, further efforts to rule out injury to the above organs should be undertaken. TM rupture in most cases can be treated conservatively.
Central tenet - The aim of central tenet is to avoid the deadly triad of hypothermia, coagulopathy and metabolic acidosis. Each condition worsens the rest of the components present in the triad.
Wound management - primary treatment
It can be difficult to initially appreciate the entire zone of some large blast injuries. Repeated debridement every 24-48 h may be indicated. , Primary closure of blast wounds greatly increases the likelihood of infection. Wounds should be left open until they are clean and granulation tissue has appeared. The wound should be ready for delayed primary closure, skin grafting or other coverage 4-6 days after primary surgery. , If repair of damaged tendons and nerves is deemed possible, they may be tagged with sutures. , Alternatively, they can be left untagged in situ for secondary surgery. 
The use of silver impregnated dressings in blast injuries
Blast injuries may cause human tissues within the tertiary injuries to become impregnated with fecal matter and other foreign bodies. Use of anti-microbial silver in conjunction with topical negative pressure greatly reduces the chances of developing sepsis or systemic inflammatory response syndrome. 
| Specific Injuries and their Management|| |
Blast lung is rare but insidious presentation is more common. Decrease in oxygen saturation or frothy sputum and inability to oxygenate may be the initial clinical picture. Subcutaneous emphysema also suggests severe pulmonary injury. High flow oxygen with endotracheal intubation and judicious fluid administration are main lines of treatment. 
Secondary penetrating injuries to the chest are frequently fatal because of the high energy and multiplicity of wounding.  Tube thoracostomy for mild degrees of hemo or pneumothorax and rarely formal thoracotomy may be required for these injuries.
Also known as blast abdomen and include abdominal hemorrhage and abdominal organ perforation. The most common organ in the abdomen to be injured is small bowel (48%), spleen (21.5%), kidney (20%) and liver (15.3%). Computed tomography (CT) scan is used for stable patients and focused assessment sonography for trauma is helpful for unstable patients. 
The clinical manifestations include abdominal or testicular pain, tenesmus, rectal bleeding, nausea and vomiting and may require primary anastomosis or repair in majority of patients. 
There is a high incidence of extremity injuries in patients who survive the initial event. , The majority of the extremity injuries are caused by penetrating secondary effects and are generally associated with severe soft-tissue and bony destruction. The primary goals of management being preservation of limb length and viable tissues for later coverage.
Mild traumatic brain injury (mTBI)
mTBI/Concussion after improvised explosive devices exposure is increasingly recognized as a sequel of primary blast injury. Altered consciousness, headache, dizziness, nausea and vomiting and difficulty in concentration are the common presenting symptoms.
Diffuse axonal injury is primarily responsible for mTBI, though contusion and subdural hematoma may contribute to the clinical picture. 
In the vast majority the symptoms of mTBI are self-limited and symptomatic treatment is all that is necessary.
When a patient present with profound shock without signs of hemorrhage, other common causes for hypotension, cardiovascular dysfunction should be suspected.  Associated lung injury is common and inotropic support may be provided.
A skeletal muscle which is compressed may release myoglobulin, urates, phosphates and potassium from the cells. Cellular death results in renal dysfunction and ultimately cardiac arrest.The main stay of treatment is aggressive hydration, alkalinization of the urine and forced diuresis.
Special considerations and care must be exercised in pregnancy, children, elderly, disabled, under water blasts and explosions in a confined space. Psychological issues must also be considered.
- Pregnancy: Injuries to the placenta are possible such as placental abruption. Hence, continuous fetal monitoring along with an expert obstetrics and gynecological consultation are the best line of management. Maternal survival takes priority and ionizing radiation to the developing fetus by investigation like CT scan is of no concern. 
- Children: History of event or complaints may be difficult to obtain in children. Pulmonary contusion is one of the most common injuries from blast thoracic trauma. Referral to specialized pediatric trauma center may be required.
- Elderly: There is a high risk of mortality and in hospital stay may be more prolonged and complicated. Orthopedic injuries may be more prevalent and blunt chest trauma should be of special consideration.
- Associated Medical Conditions: Priority should be given to patients with pre existing medical conditions and it may be stressed that untreated or inadequately treated fractures may lead to severe and long lasting morbidity.
- Underwater blast:  If a blast occurs underwater, there is a compounding effect of the energy as blast wave attempts to pass through water, which is greater in density than air. However, it also dissipates more quickly and the shrapnel travels a short distance as friction reduces its velocity. Greater blast energy is imparted on the abdomen than the lungs resulting in more abdominal injuries.
- Explosion in a confined space/vehicle: Here blast wave gets repeatedly reflected from the walls, ceiling and floors producing complex blast wave.  There is higher incidence of primary blast injuries, which are more severe in nature causing in greater mortality.
- Psychological Issues: The common sequel from an explosive event includes anger, frustration, helplessness and desire to seek revenge and may require psychological counselling.
| Conclusion|| |
Patients with blast injuries are difficult to manage because their most obvious injuries may not be the most likely to contribute to their mortality. Blast injuries may cause lots of casualties with lots of injuries. SB trauma is the biggest killer. Blast injury survivors may present with graphic injuries, from full thickness burn to full or partial amputation. These patients are best managed in advanced trauma centers.
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