Burn injuries are tissue injuries caused due to the application of heat of any form to the external or internal body surface. The injuries can be minor or sometimes severe and life-threatening. Burns sometimes happen when in contact with naked flame or a heated element of an electric wire/glass/hot metals. The worst burns in domestic circumstances are those due to the ignition of clothing that accidentally comes in contact with coal, gas, stove.
The application of the heat that causes burns may be in the form of dry or moist heat, mechanical injuries causing friction like brush burns or friction burns, burns due to corrosives, burn due to lightning/electricity, burns due to radiation, X-rays, UV rays, radium, laser, etc. In case of first-degree burns then it affects the epidermal layer and erythema and blisters can be seen. In second-degree burns, deep layers of skin get affected, and hence healing leaves a scar.
The depth of the injury depends on temperature applied, duration of contact, thickness of the skin, blood flow. Techniques like clinical assessment, biopsy and microscopy, vital dyes, ultrasound, fluorescent fluorometry, laser doppler flowmetry, thermography, light reflectance method, MRI scan, and radioactive isotopes are used to estimate the depth of the burns.
The immediate cause of death can be Neurogenic shock, hypovolemic shock, inhalation of smoke, inhalation of carbon monoxide, laryngeal edema, injuries sustained while trying to escape, etc. the delayed cause of death might be a septicemic shock, toxemia, renal failure, ARDS, fat embolism, pulmonary embolism.
Patho-Physiology of Burn Injuries
Burn injuries can cause coagulative necrosis of the epidermis and the underlying tissues. It will bring in cellular damage primarily by the transfer of energy thus inducing coagulative necrosis. In addition to the heat, direct injury to the cell membrane can be caused by chemicals or electricity. The burn injury of the skin has been divided into three zones of coagulative necrosis.
- The Zone of Coagulation is where the damage caused is irreversible. This is the necrotic area of the burn.
- The Zone of Stasis has a moderate degree of cellular insult with decreased tissue perfusion. Depending on the severity of the causative agent and body environment the cells may survive or go on to coagulative necrosis. Vascular damage and vessel damage can be seen in this zone.
- The Zone of Hyperemia is characterized by vasodilation from the inflammation. The cells are not severely damaged and hence will have viable tissues from which the healing process begins.
Types of Burn Injuries
- Suicidal Burns: In India, these are commonly seen in the domestic environment and are mostly seen in females. Inflammable material like kerosene or petrol is used. At times superficial burns may be inflicted over the accessible parts of the body for false accusation against the enemy.
- Accidental Burns: These happens when a victim gets trapped in a burning vehicle or a building/room. Another situation is when the clothing catches fire while cooking, sitting, or working near a stove or gas, or open lighted kerosene lamps.
- Homicidal Burns: These are the cases where a person tries to hurt someone or murder someone by burning the victim with fire. These types of burns are caused by criminal intent.
- Moist Heat Burns: These are also known as scalds resulting from the application of hot liquid above 60℃ or due to steam. In this mostly the superficial skin layers are affected. But if the liquid is in the form of an oil, syrup, hot tar, then the injury can be comparatively deeper.
- Dry Heat Burns: These occur due to contact with a dry heat source such as fire or a hot object.
Age of Burn Injury
- Erythema appears immediately after the burns
- Vesication usually develops within 2-3 hours after death.
- Inflammatory reaction intensifies, polymorphonuclear cell infiltration, epidermis coagulation can be seen within 6-12 hours.
- The exudate begins to dry in 12-24 hours and within 24-72 hours it forms a dry, brown crust and the inflammatory zone begins to disappear.
- If infection happens, then pus is formed in 2-3 days but not before 36 hours.
- Superficial sloughs usually separate from the 4th to 6th day and deeper sloughs take about 2 weeks.
- During fortnight granulation tissue covers the surface and healing occurs from the periphery
- Within a few weeks to months small areas start to heal with scar formation, the large area sees the formation of cicatrix and deformity.
Difference Between Antemortem and Postmortem Burns
|Features||Antemortem Burns||Postmortem Burns|
|Carboxyhemoglobin in blood||Present||Absent or low level|
|Cyanide in blood||Present||Absent or low level|
|Carbon/soot in Respiratory Passage||Present||Absent|
|Blisters||Present and will contain serous fluid rich in protein and chlorides The base is red, inflamed with raised papilla||Absent. If present will contain air and clear fluid. The base is Dry, pale, or yellow, hard.|
|Line of redness||Present around the burn area||Absent|
It is important to understand the features and types of burn injuries. The autopsy findings will help in understanding whether it was a suicidal, homicidal, or accidental burn. In India, cases of bride burns and dowry death are common.
In the case of burn injuries, it is necessary to identify the cause of death, whether the burns are antemortem, or postmortem and whether the antemortem injuries or burns were sufficient to cause death.
Understanding the age of burn injuries will help to understand the estimated time and date of the occurrence of the event. If burns involve face with charring then it will be difficult to identify the victim.