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Thermal Injuries

Tissue damage due to application of heat is termed as a thermal injury.

Types of Thermal Injuries

1. Dry heat burns (Direct heat application)

By application of hot substances and by flames

2. Moist heat burns or Scalds(Hot fluid application)
3. Radiation burns

Due to X-rays, UV rays, radium, laser, etc.

4. Electric burns

Due to electric contact, electric spark, flashes of lightning

5. Chemical burns or corrosive burns

Extent of Thermal Injuries

They may range from mild erythema (redness) to total incineration of body tissues.

Severity of Thermal Injuries

Severity of thermal injuries depends upon:

  1. Temperature
  2. Duration of contact

In children 20% body surface burns are considered life threatening, whereas in adults 40% or more are generally fatal.

Rule of Nines

The estimation of burnt surface areas in adults is usually worked out by the rule of nine. In children, estimation of burnt surface is worked out by use of Lund and Browder chart.

Area of body Percentage
Head and neck 9%
Front 18%
Back 18%
Arm 9%
Front of Leg 9%
Back of leg 9%
Genitals 1%

Dry Heat Burns (Wilson’s three stage classification)

First Degree Burns (Epidermal)

There is erythema and blistering without loss of epidermis. Healing is excellent without scarring.

Second Degree Burns (Dermo-epidermal)

There is destruction of full thickness of the skin. Injury does not heal without scarring.

Third Degree Burns (Deep tissues involved)

Tissues deep to the skin are also burned. Even the whole limb may be completely burnt.

Causes of Death in Burns

Immediate Causes

  1. Asphyxia (due to smoke, CO)
  2. Primary neurogenic shock (due to pain, fear)
  3. Accidental injuries (falling structures)

Late Causes

  1. Secondary hypovolemic shock (due to serum exudation)
  2. Fat embolism
  3. Acute tubular necrosis
  4. Sepsis of burns –silver nitrate is used to prevent burn sepsis
Post Mortem Appearances

These depend upon:

  1. Degree of burns
  2. Duration of burning

External Postmortem Findings

  1. Burnt area may be reddened, blistered or charred
  2. Blisters contain albuminous fluid with high chloride content and RBCs
  3. Deposits of carbonaceous material on the body
  4. Portions of the body with tight clothing may escape burns e.g. belt area or strangulated neck
  5. Hypostasis is cherry red (due to CO)
  6. Pugilistic attitude or boxer like attitude
  7. Heat splits of skin; may be confused with incised or cut wounds
  8. Heat fractures
  9. Heat hematomas

Internal Post-mortem Findings

  1. Internal organs resist burning due to insulation
  2. Soot and smoke residues are found in trachea and lungs when burnt alive
  3. Blood is thick and cherry red (due to CO)
  4. Carbon monoxide can be demonstrated by Kunkel’s test on blood
  5. Internal organs are looked for other evidence or injuries
Forensic Significance
  1. Identity of deceased
  2. Whether the burns are post mortem or ante mortem?
  3. Whether the burning is actual cause of death?
  4. Accidental, suicidal or homicidal>
  5. Peri-mortal injuries are those which have occurred a few minutes before death. They do not show inflammation. They may or may not be the cause of death. These injuries cannot be assigned as ante-mortem or post-mortem injuries.
  6. First degree burns due to hot liquids show no effect on hair and thus can be differentiated from burns due to dry heat.
  7. Internal organs are usually preserved due to insulation and high body water content. Thus helping in identification of a person for sex. A person dying of MI and then later on burnt, will have evidence of MI. Stab wounds may be visible I internal organs if not through external examination.
  8. Despite severe burning of the exterior of the body, the teeth are often well preserved, enabling identification.
  9. Tongue, trachea and main bronchi show soot, if the person is breathing whilst caught in fire. Histologically carbon particles are found in bronchioles.
  10. Pugilistic Attitude

Pugilistic attitude involves heat flexures of the limbs. The elbows, knees and wrists are strongly flexed due to coagulation of proteins.

Moist Heat Burs (Scalds)

  • The responsible liquid may be seen over clothes or the body. Trickle marks are present.
  • Only superficial layers of skin are affected.
  • No singeing of hair or charring is seen.
  • Usually accidental but may be caused by intent.

Classified into three degrees:

  1. Redness
  2. Blistering
  3. Necrosis of the dermis

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