Thermal Injuries

Written by Dr. D. Rao


A burn is an injury which is caused by application of heat or chemical substances to the external or internal surfaces of the body, which causes destruction of tissues. The minimum temperature for producing a burn is about 44oC for an exposure of about 5 to 6 hours or about 65oC for two seconds are sufficient to produce burns.

Varieties of Burns: The external appearances of burns vary according to the nature of the substance used to produce them.
  1. A highly heated solid body or a molten metal, when applied to the body for a very short time may produce only a blister and reddening corresponding in size and shape to the material used. It will cause destruction, or even charring of the parts, when kept in contact for sometime. The epidermis may be found blackened, dry, and wrinkled. The hair may be singed or distorted.
  2. Burns produced by flame may or may not produce vesication, but singeing of the hair and blackening of the skin are always present. Hair singed by the flame becomes curled, twisted, blackish, breaks off or is totally destroyed. Roasted patches of skin or deeper parts may be seen.
  3. Burns caused by kerosene, oil, petrol, etc. are usually severe and produce sooty blackening of the parts and have a characteristic odour.
  4. Burns caused by explosions in coal mines or of gunpowder are usually very extensive and produce blackening and tattooing due to driving of the particles of the unexploded powder into the skin.
  5. Burns due to X-ray and radium vary from redness of the skin to dermatitis, with shedding of hair and epidermis and pigmentation of the surrounding skin. Severe exposure may produce burns with erythema, blistering or dermatitis, or ulceration with delayed healing and ill-formed scars. Fingernails may show degenerative changes and wart-like growths. Infra-red rays may cause necrosis of the skin.
  6. Burns caused by ultraviolet rays (the sun or mercury vapour lamp) produce erythema or acute eczematous dermatitis.
  7. Burns from corrosive substances show ulcerated patches and are usually free from blisters’ hair is not singed and red line of demarcation is absent. They show distinct coloration and are usually uniform in character. Strong acids produce dark leathery burns upon the skin. Strong alkalis cause the skin to slough and leave moist, slimy, grayish areas. Hydrofluoric acid and bromine cause necrosis of the skin and tissues.
  8. Electrical burns.

Degree of Burns: Dupuytren divided burns into six degrees, but they were merged into three degrees by Wilson. The precise depth of a burn can be measured by a high frequency ultrasound device.
  1. Epidermal: (first and second degree Dupuytren).
  2. Dermo-epidermal: (third and fourth degrees Dupuytren).
  1. Deep: (fifth and sixth degrees, Dupuytren): In this, there is a gross destruction not only of the skin and subcutaneous tissue, but also muscles and bones are destroyed, and as such the burns are relatively painless. The appearances are similar to those of the second degree, but in a more severe form. The burnt part is completely charred.

Effects: The effects depend on:
  1. The degree of heat: The effects are severe, if the heat applied is very great. The body of an adult does not burn completely in a burnt house, as the temperature usually does not exceed 650oC. For purpose of cremation, a human body has to be incinerated for one and half hours at 1000oC. The ashes weigh 2 to 3 kg., and contain bone fragments which can be identified as human.
  2. The duration of exposure: The symptoms are more severe if the heat is applied for a long time.
  3. The extent of the surface: The estimation of the surface area of the body involved is usually worked out by the “rule of nine”, 9% for the head and each upper limb; 9% for the front of each lower limb; 9% for the front of chest; 9% for the back of chest; 9% for the front of the abdomen; and 9% for the back of abdomen, 99% of the body. The remaining 1% is for the external genitalia. Involvement of 50 percent of the body surface will prove fatal even when the burns are only of the first degree.
  4. The site: Burns of the head and neck, trunk or the anterior abdominal wall are more dangerous.
  5. Age: Children are more susceptible, old people less.
  6. Sex: Women are more susceptible.

Causes of Death: (1) Primary (neurogenic) shock due to pain, etc. (2) More than half of deaths from burns occur within the first 48 hours usually from secondary shock, due to fluid loss from burned surface. (3) Toxaemia, due to absorption of various metabolites from the burnt tissue persists up to 3 to 4 days. (4) Sepsis is the most important factor in deaths occurring 4 to 5 days or longer after burning. (5) Biochemical disturbances, secondary to the fluid loss and destruction of tissue, e.g., hypokalemia. (6) Acute renal failure, due to lower nephron nephrosis occurs on the third or fourth day. (7) Gastrointestinal disturbances, such as acute peptic ulceration, dilation of the stomach, haemorrhage into intestines. (8) Oedema of glottis and pulmonary oedema due to inhalation of smoke containing CO and CO2, if the person dies in a burnt house. (9) Accident occurring in an attempt to escape from a burning house or by injuries due to falling masonry, timber or other structures on the body. (10) Pyaemia, gangrene, tetanus, etc. (11) Fat embolism is rare. (12) Pulmonary embolism from thrombosis of veins of the leg due to tissue damage and immobility.

Post-mortem Appearances:

External: The clothes should be removed and examined for the presence of smell of kerosene, petrol, etc. They should be put into airtight bottles and sent for chemical analysis. It is difficult to determine the time of death as body temperature, post-mortem hypostasis and rigor mortis cannot be assessed. The burnt areas will be found reddened and blistered or charred. Blisters may be present either in the main burn or as islands beyond the periphery. The whole of the burned area may form one large blister or be confluence of blisters. The degree of burning in each area should be assessed. Hair is singed, or completely burnt. In lesser degrees of burns, ends are bulbous at intervals. Heat rigor may be observed in the muscles. Portions of the body where clothing is tight, e.g., under the belt, shoes, brassier or buttoned collar are often comparatively unaffected. Sometimes, skin and hair in the armpits and the gums are spared. The colour of light hair changes on exposure to heat. At about 120oC for 10 to 15 minutes, brown hair becomes slightly reddish. There is no change in the colour of the black hair. The face swollen and distorted. The tongue protrudes and may be burnt due to the contraction of the tissues of the neck and face. Froth may appear at the mouth and nose due to pulmonary oedema caused by heat irritation of the air-passages and lungs. In the hands, the skin detaches as glove, including the fingernails. By removal of the superficial layers of the skin by wiping  or rubbing, tattoo marks become visible. The blisters of a second degree burns cannot be distinguished from blisters seen in CO poisoning, deep coma, ante-mortem and post-mortem gasoline exposure and peeling of the skin seen in the early stages of putrefaction. When these various types of blisters burst, they leave a pale, moist, raw surface which becomes yellow, tan and finally dark brown and leathery as it dries.

Pugilistic Attitude (boxing, fencing, or defence attitude): The posture of a body which has been exposed to great heat is often characteristic. The legs are flexed at the hips and knees, the arms are flexed at elbows and wrists and held out in front of the body, all fingers are hooked like claws, contraction of paraspinal muscles often causes a marked opisthotonus, in an attitude commonly adopted by boxers. This stiffening is due to the coagulation of proteins of the muscles and dehydration which cause contraction. The flexor muscles being bulkier than extensors contract more. It occurs whether the person was alive or dead at the time of burning.

Heat Ruptures: If the heat applied is very great, skin contracts and heat ruptures occur, either before or after death. They are produced by splitting of the soft parts. These splits may be anywhere, but are usually seen over extensor surfaces and joints. These ruptures or splits in the skin may be several centimeters in length, and superficially they may resemble lacerations or even incised wounds. They can be differentiated by: (1) Absence of bleeding in the wound and surrounding tissues, since heat coagulates the blood in the vessels. (2) Intact vessels and nerves are seen in the floor. (3) Irregular margins. (4) Absence of bruising or other signs of vital reaction in the margins.

Sometimes, the charred skin cracks easily when an attempt is made to remove the body from a house destroyed by fire. These tears are commonly seen around joints, especially the elbows, shoulders and knees.

“Flash burns” refer to thermal burns due to sudden, brief exposure to flame. This type of exposure is common in explosions, or ignition of fine particulate material or upon ignition of highly inflammable liquids. All exposed surfaces are burned uniformly. If clothing is ignited, a combination of flash and flame burn occurs.

Human bodies burn readily, especially when the subcutaneous fatty tissues have ignited. Often, some parts of the body are preserved, if they are protected from the flames. In sitting persons, the buttocks may be spared; if the head falls forward between the knees, the abdomen is spared. The hands and feet may drop off if the burning is sudden and intense, and they may be preserved with slight damage because they fall away from the source of fire. Flexion of the limbs by heat may cause tumbling of a burnt body from a bed or chair to the floor, if the body was not well balanced. Partial burning of the abdominal wall associated with gas expansion within the intestines may produce rupture of the abdominal wall, in the charred burnt victim. The intestines may protrude through this defect. Flame burns usually have a patchy distribution and vary in size and shape. Sometimes, the body may be covered with a black or brown layer of smoke which does not penetrate into skin creases. On straightening the flexed neck or limb, the paler skin in the crease is exposed which may mimic a ligature mark. In severe burns, the skin may be stiffened, yellow-brown and leathery. Drying after death leaves a stiff, parchment-like surface. Muscles under the burnt area are pale, brownish and part-cooked. This occurs after death due to heated environment. Black, brittle masses are found in the tissues merging into cooked dry muscle beneath. Brunt bone has a gray-white colour, often showing a fine superficial network of heat fractures on its cortical surface. The soft tissue of the face may be completely burnt exposing the skull. The outer tables of the exposed cranial vault may show a network of fine criss-crossing heat fractures. If the flame is unchecked, the body will be reduced to a shapless, carbonaceous mass and finally to heap of grey and yellow ashes.

Establishment of Identity: In a charred body, the weight and stature are unreliable, as they are greatly altered due to drying of the tissues, skeletal fractures, and pulverization of intervertebral discs due to the heat. The stature may be less by several centimeters and weight loss may be up to 60%. The features are changed due to contractions of the skin. Moles, scars and tattoo marks are usually destroyed. Dental charts should be prepared and X-rays of the jaws taken, which can be compared with previous charts of the suspected person. Complete X-rays of the body of the victim are useful to locate possible old fractures, bony abnormalities or foreign bodies. In a badly charred or incinerated body, the sex can be determined by finding the uterus or prostate which resist fire to a marked degree, and by pelvic bones, and age by teeth and by observing centers of ossification in the bones and the condition of the epiphyses. If the whole body is destroyed, personal effects such as keys, watch, buttons, belt-buckle, cuff-links, etc., may help in identity.

Internal: Heat haematoma occurs when the head has been exposed to intense heat, sufficient to cause charring of the skull. It has the appearance of extradural hemorrhage, but is not accompanied by any signs of injury by blunt force. It consists of a soft, friable clot of light chocolate color, and may be pink, if the blood contains CO. The clot has a honeycomb appearance. The thickness of the clot varies from 1.5 to 15mm, and the volume up to 120 ml. The adjacent brain shows hardening and discoloration from the heat. The distribution of the clot follows closely the distribution of the charring of the outer table of the skull. The parietotemporal region is the most common site of such hemorrhage. The mechanism of its development is obscure. Possibly, the blood, may come from the venous sinuses or the diploic veins by the shrinkage of the brain due to heat.

The skull fractures occur most commonly in areas where the skull has been severely burned. There are two types of thermal fractures of the skull. (1) Intracranial increase of steam pressure causes separation of ununited sutures or an intracranial explosion occurs, producing fractures with gaping defects and widely separated bony margins. (2) The fracture occurs due to rapid drying of the bone with contraction, and only involves the outer table of the skull. In this type there is no displacement, and the lines of fracture are frequently stellate. Skull fractures are usually seen on either side of the skull above the temples. They consist of several lines which radiate from a common centre. Heat fractures usually do not involve the sutures of the skull even in young persons with un-united sutures. Heat fracture may cross a suture line. Peculiar, characteristically curved fractures are often seen in bones of extremities exposed to very high temperatures.

Even in cases of severe external charring, the internal organs are usually well preserved, as the tissues of the body are poor heat conductors. Sometimes, brain, liver, lung, etc., may be cooked, i.e., hardened and discoloured. In death due to burns, the CO levels in the blood will be more than 10% and may reach 70 to 80%, though children and old person die at levels of 30 to 40%. The blood is cherry-red, which may change to brownish due to heat. The level of CO saturation of the blood is dependant on concentration of CO in the inhaled air, the duration of exposure, the rate and depth of respiration, the haemoglobin content of the blood and the activity of the victim. CO may be absent in blood due to various reasons, such as rapid death, convection air currents, low production of CO, flash fire (as in the conflagration of a chemical plant.), inhalation of superheated air resulting in death by suffocation, in warfare, or in an explosion when death is instantaneous. If death has occurred from suffocation, aspirated blackish coal particles are seen in the nose, mouth, larynx, trachea, bronchi, esophagus and stomach and blood is cherry-red. Such particles are embedded in frothy mucus which covers the congested mucosa. The presence of carbon particles in the terminal bronchioles on histological examination is absolute proof of life during the fire. The soot is better seen by spreading a thin film of mucus on a clean sheet of white paper. The amount of soot in the air-passages depends on the type of fire, the mount of smoke produced and the duration of survival in the smoke-contaminated atmosphere. Presence of carbon particles and an elevated CO saturation together are absolute proof that the victim was alive when the fire occurred. If the mouth is open, some passive percolation of soot may be found at the back of the pharynx, but it cannot be carried beyond the vocal cords, and also it is not found in the lower esophagus and the stomach. In absence of CO in blood and soot in the airways, death may result possibly due to poisoning with CO2 and/or O2 deficiency. Poisonous gases like cyanide and oxides of nitrogen are produced due to burning of plastic and synthetic material. Burning of nitrogen containing substances, e.g. nitrocellulose film may liberate nitrogen oxide and nitrogen tetroxide. Burning of wool or silk liberate ammonia, hydrogen cyanide, hydrogen sulphide and oxides of sulphur. All these gases contribute to death. depending on the materials burning in the fire, various levels of cyanide are found in the blood, but the levels are usually less than 0.3 mg.%. Cyanide can be produced in significant concentration by decomposition of the body. Blood should be preserved by fluoride for analysis of cyanides. If flame or superheated air is inhaled, burns are seen in the interior of the mouth, nasal passages, larynx and air-passages with destruction of vocal cord epithelium and acute edema of the larynx and lungs. Death may occur rapidly by shock or acute respiratory insufficiency. The interior of the larynx, trachea and main bronchi may be thickened and blanched, or reddened. If the victim survives for a few days, inflammatory changes occur in the larynx, with sloughing of mucosa, ulceration and secondary infection.

Haemoconcentration is present, and frequently there is some tissue edema and excess of fluid in the serous cavities. The brain is usually shrunken, firm and yellow to light-brown due to cooking. The dura matter is leathery. The dura may split and the brain tissue may ooze out, forming a mass of frothy paste. The pleurae are congested or inflamed. The lungs are usually congested, and show marked edema; they may be shrunken and rarely anaemic. The vessels of the lungs may contain a small amount of fat due to a physico-chemical alteration of fat already present in the blood. Visceral congestion is marked in many cases. Petechial haemorrhages are usually found in the pleurae, pericardium and endocardium. The heart is usually filled with clotted blood. There may be inflammation and ulceration of Peyer’s patches and solitary glands in the intestines. Occasionally, ulcers are produced in the duodenum (Curling ulcers), about the tenth day in extensive burns of the body. Curling’s ulcers are usually sharply punched-out mucosal defects, which may be superficial or deep. Petechiae of stomach and duodenum, often with erosions, occasionally acute ulcers, is a more common finding. The large boel may also be involved. The spleen is enlarged and softened. The liver may show cloudy swelling. Fatty liver is not due to burns, but due to treatment with tannic acid. Jaundice may occur. The kidneys may show cloudy swelling, capillary thrombosis and infarction. The adrenals may be enlarged and congested. When more than 30%  of the skin surface is burnt, haemoglobinuria occurs. Depending on the materials burning in the fire, various levels of cyanide are found in the blood but the levels are usually less than 0.3 mg%.

Laryngeal Oedema: It may be caused by allergic anaphylactic reactions, infections, tumors, inhalation of flame or superheated air, inhalation of irritant gases, etc. the amount of oedema will decrease with post-mortem interval and only wrinkling of mucous membrane may be present. Microscopically, eosinophils may be seen.

Blood should be obtained from the heart or major vessels and placed in a tightly stoppered container. It need not be collected or kept under oil. If blood is clotted, the clot should be preserved.

Age of Burns: The ageing of the burns is very inaccurate and depends upon the agent, the extent, and their depth. Redness appears immediately, and vesication in about an hour. The exudates beings to dry in 12 to 24 hours and forms a dry, brown crust within 2 to 3 days. The red inflammatory zone disappears in 36 to 72 hours, and pus may form under sloughs. Superficial sloughs fall off in 4 to 6 days, and deeper sloughs within two weeks. After this, granulation tissue covers the surface and a scar is formed after several weeks.

Ante-mortem and Post-mortem Burns: In ante-mortem burns, a zone of hyperaemia (line of redness), which varies in width, but is usually 5 to 20 mm. is present at the edge of the burnt area, except in cases of immediate death. it is due to oedema of tissues and capillary dilatation and merges with the edge of the burn which may shows blistering or charring. It involves whole thickness of true skin. It is permanent and persists after death. if the whole body is burnt, line of redness will be absent. The ante-mortem blister appears as a raised dome and contains gas or fluid. The base and periphery show reddening with swollen papillae. Post-mortem blister is dry, hard and yellow. The protein content of serous fluid is not of much value to differentiate ante-mortem and post-mortem burns. In ante-mortem burns, the skin adjacent to burnt area shows an increased reaction for SH groups in all layers, and increase in enzyme reaction. Acid mucopolysaccharides are present in the superficial zone of burnt area. Burns produced shortly before or after death cannot be distinguished either by naked eye or by microscopic examination.

Circumstances of Death: The distribution of burns on the clothing may indicate the manner in which it was ignited, the posture of the victim at the time, the path taken by flames and to discover that unburnt cloth was saturated with some inflammable material. Splash patterns burnt into the floor and floor coverings, holes in the floor, particularly holes of the ‘tongue and groove’ type and the characteristic odour of petroleum fuels and solvents are all useful indicators of the use of inflammable material. Differentiation is mostly a matter for the police investigation. The inhalation of CO often causes severe muscular in coordination, weakness, and confusion due to which the victim is unable to escape and dies of asphyxia, the body being burnt after death.

Accident: Large numbers of deaths are accidental. Infants, children, epileptics, intoxicated or drugged persons or helpless from other causes may fall into a fire. When an intoxicated person goes to bed smoking, and drops a lighted cigarette, he may die due to burns. Lamps or stoves may explode and set fire to the clothes. Clothes of women may catch fire accidentally while cooking. In such cases, burns are usually found on the front of thighs, abdomen, chest and face. There may be severe burning of the hands due to the victim trying to extinguish the fire by beating out the flames. The feet and ankles are usually not burnt. Multiple deaths from burns may result from plane crashes or automobile accidents. In industry, burns may be caused by explosions from inflammable liquids and by flashes from furnaces. The skin resting on the surface is well preserved.

Suicide: Occasionally, women commit suicide by pouring kerosene on their clothes before setting fire to themselves due to domestic worries, disappointment in love or acute or chronic disease. Extensive burns are seen over the whole of the body; only the skin folds, such as the axillae and the perineum being spared. Sometimes, a person may keep a piece of cloth in her mouth to suppress her cries. Sometimes, suicidal burning is a mode of public protest. In case kerosene, petrol, etc. is found on the body including head hair in high amounts, it is likely to be either suicide or homicide.

Homicide: Murder by burning is rare. If an inflammable fluid such as kerosene, petrol, etc., is poured on a person lying on his back and then burnt, there will be burning of the sides of the neck, sides f the trunk, between the thighs and other areas, especially if the clothing is absent in those areas, as the fluid runs downwards. Sometimes, fire, hot metals, boiling water and corrosive substances are used with criminal intent. A drunken man may push or throw his wife or child on the fire, and sometimes lighted lamps may be used as missiles. Burns may be inflicted on the pudenda of women as a punishment for adultery. Attempts may be made to burn a body after homicide with the object of concealing the crime. In such cases, the body should be examined for marks of violence, e.g., stab wounds, bullets, strangulation, etc. In cases of Individual dying due to Extensive burns  under  Alcohol intoxication/influence of drugs no accidental nature should be specifically ruled out.

Self-inflicted Burns: Burns are sometimes self-inflicted in order to support a false charge.

In some instances, burnt bones and ashes are forwarded to the forensic  pathologist for inspection, if the police suspect some foul play after a body is partially or completely burnt. In an ordinaryhouse fire, the temperature seldom exceeds 1200oC. It is, therefore, unlikely that the body of an adult will burn so completely as to leave no trace. If the body is not completely consumed, fragments of bones left would afford sufficient evidence to indicate whether they were human or not. The combustion of a body is rarely so complete as to reduce it to ashes. Hence, by shifting the ashes through sieves, fragments of bones can be collected and identified by a careful study.

Incineration of an adult human body for the purpose of cremation requires 1 ½ hour at 1600-1800oC, and the resultant ashes weigh about 4-6 kg. Such human ash contains bone pieces which may still be identified.

Todd and Krogman working on a body burned in an auto, concluded:

When the soft tissue around the bones are small in amount (thin) the bones show sharp heat induced fractures of the skull and limb-bones (usually transverse), charring, calcining and splintering, while with thick soft tissue, e.g., in femur, pelvis and nuchal areas of skull the substance of the bones shows the molten or guttered condition characteristic of fusion by heat.

A bone is white in appearance when burnt in the open, and black or ash grey when burnt in the closed fire. A burnt bone preserves its shape, but falls to powder when pressed between the fingers. It is said that it will be reduced to charcoal if treated with hydrochloric acid, but this is not necessarily true. If it is burnt to such an extent that organic matter is destroyed, no charcoal will be left on adding acid. When exposed to very high temperature, characteristically curved fractures may be produced in long bones and skull. A bone becomes so brittle and friable on prolonged exposure of the fire victim to such intense heat, that it is readily fractured during transport of the body, or its being moved, or during examination. A hyoid bone may similarly break on manipulation. A forceful stream from a fire-hose can fragment a bone like the femur, rendered brittle by exposure to such high temperatures. The skull bursts due to the formation of steam within the skull cavity as a result of intense heat. Such explosive post-mortem fractures are accompanied by gaping defects and separation of non-united sutures and protrusion of brain matter. Intense heat can lead to desiccation of skull, with the production of post-mortem thermal linear fracture, commonly located on either side of the skull, above the temples. They usually consist of several lines which radiate from a common centre. If the appearance is not typical, distinction from an ante-mortem skull fracture may be difficult. Besides, post-mortem mechanical fracture of any bone, due to the fall of a wall or a beam can also occur. It is important, therefore, to distinguish between post-mortem thermal fracture and post-mortem mechanical fracture.

In cases of suspected poisoning by some mineral, eg, arsenic, all the available ashes and burnt bones should be preserved for chemical analysis. This is because, despite its volatility, it is possible to detect arsenic in large pieces of burnt bones mixed with ashes in cases of arsenic poisoning, for the following reasons.

  1. Much of the arsenic in bones is converted into arsenates, partially replacing the phosphates of the bones. Arsenates are non-volatile; hence arsenic can be detected in the bones even after strong heating for a long time.
  2. Even if all the arsenic were present in the bones in the form of arsenic trioxide or some other volatile form, all the arsenic is not likely to be lost during the process of cremation, as complete combustion of a body does not, as a rule, occur in India. Hence, some of the volatilized arsenic is liable to be condensed on the cooler parts of the unburnt funeral pyre, where its presence may be detected.
When arsenic trioxide is heated with salts of sodium or earth group, part of the arsenic is converted into arsenite and becomes non-volatile.

The medico-legal investigation of a death from burns should be aimed at answering the following questions.

  1. Was the person alive before fire started?
  2. Did the burns cause death
  3. If death was from causes other than burns, did the burns contribute to death?
  4. Were there any natural diseases or injuries that could have caused death or contributed to
  5. Were the burns sustained accidentally or did the person commit suicide?
  6. Was the death of crime?
  7. Was there any attempt to conceal crime?
  8. What was the cause of the onset of fire?
  9. What evidence was found to identify the decedent?
Occasionally, with multiple fatalities, one may be asked who died first.

Examination of scene may reveal information regarding the cause of fire and may also in the site of origin of the fire. The overall study of the circumstances of death at the scene may information concerning the manner of death.

From the scene of death all personal belongings such as keys, watch band, bell buckle, button cuff links and pieces of unburned clothing should be collected. These can be helpful in established the identity of the decedent.

Three clinical conditions any result from exposure to high environmental temperature: (1) heat cramps, (2) heat hyperpyrexia, and (3) heat prostration.

  1. Heat Cramps: (miner’s cramps, stoker’s cramps, or fireman’s cramps): They are caused by a rapid dehydration of body through the loss of water and salt in the sweat. It is seen in workers in high temperature when sweating has been profuse,. The onset is usually sudden. Severe and painful paroxysmal cramps affecting the muscles of the arms, legs and abdomen occur. The face is flushed, the pupils dilated and the patient complains of dizziness, tinnitus, headache and vomiting. Intravenous injection of saline gives rapid relief.
  2. Heat Hyperpyrexia or Heat Stroke: Heat stroke is a condition characterized by rectal temperature greater than 41oC; and neurological disturbances, sucha s psychosis, delirium, stupor, coma, and convulsions. The term thermic fever or “sunstroke” is used when there has been direct exposure to the sun. High  temperature, increased humidity, minor infections, muscular activity, and lack of acclimatization are the principal factors in the initiation. Where there is 100% humidity, a temperature of 32oC in the environment may lead to heat stroke. Other factors are old age, pre-existing disease, alcoholism, use of major tranquilizers, obesity, lack of air movement and unsuitable clothing. Failure of cutaneous blood flow and sweating, the factors which control body temperature, leads to a breakdown of the heat regulating centre of the hypothalamus.

Clinical Features: The onset is usually sudden, with sudden collapse and loss of consciousness. In some cases, prodromal symptoms of headache, dizziness, nausea, vomiting, weakness, mental confusion, muscle cramps, restlessness and excessive thirst occur. The temperature rises to 40oC to 43oC or more. The skin is dry, hot and flushed, with complete absence of sweating. The pupils are contracted,. The pulse is rapid (usually more than 130 p.m.) and later becomes irregular. The breathing is rapid, (usually above 30 breaths p.m.) deep and of Kussmaul type. Blood pressure is low. Convulsions occur and the patient becomes delirious or comatose. The fatal period is 5 minutes to 3 days.

Post-mortem Appearances: They are not specific. The temperature remains high after death. C.N.S: The brain is congested and edematous and petechial hemorrhages are seen in the white matter . cerebral hemispheres are increased in weight and show flattening of the convolutions. Cellular changes with pyknotic nuclei, swollen dendrites, chromatolytic changes, degeneration of neurons and diffuse proliferation of mocroglia are seen. Changes occur in cerebellum rapidly which are more striking and consistent and consist of oedema of the Purkinje layer and swelling, disintegration and reduction of the Purkinje cells. If the person survives for 24 hours, complete degeneration of the Purkinje layer and gliosis are seen. Rarefaction of the granular layer occurs with prolonged survival. Hypothalamus shows oedema of the nuclei. Respiratory system: Trachea and bronchi contain frothy hemorrhagic fluid. The lungs show oedema, congestion and hemorrhages. Heart: Dilation of right auricle, flabbiness of muscle, petechial or confluent subepicardial and subendocardial hemorrhages and degeneration of myocardium. Liver: Congestion and centrilobular necrosis. Kidneys: Congestion, oedema and increase in weight. In case of longer survival, haemoglobinuric nephrosis is common. Adrenals: Pericapsular hemorrhages, engorgement of sinusoids and cortical degeneration. General: Petechial and confluent haemorrhages are seen in most organs.

  1. Heat Prostration(heat exhaustion; heat syncope, or heat collapse): Heat prostration is a condition of collapse without increase in body temperature, which follows exposure to excessive heat. It is precipitated by muscular work and unsuitable clothing. There is extreme exhaustion and peripheral vascular collapse. The patient feels suddenly weak, giddy and sick. He may stagger or fall. The face is pale, the skin cold, the temperature subnormal. The pupils are dilated, the pulse small and thready and the respiration sighing. The patient usually recovers if placed at rest, but death may take place from heart failure.



A scald is an injury which results from the application of liquid about 60oC or from steam. The destruction does not extend as deeply as in burns. Redness appears at once and blistering will take place within a few minutes. If blistered skin is removed, it will leave a pink raw surface and later the exposed dermis becomes brownish, hard and dry. Scalds show saddening and bleaching but do not singe the hair, and do not blacken or char the skin. Superheated steam soddens the skin which becomes dirty white colour.

Degrees of Scalds: (1) Erythema by vasoparalysis, (2) Blister formation due to increased permeability of the capillaries, (3) Necrosis of the dermis.

The injury is limited to the area of contact and is more severe at the point of the initial contact. Scalding can occur through clothing. Scalded areas are usually large, but may be small if caused by splashing. Streaks of liquid run downwards from the main area causing lines of blisters. Sticky liquids. Such as syrup, oils and tar cause more severe scalds than hot water. There is usually a sharply demarcated edge, corresponding to the limits of contact of the fluid. The scalded skin may swell and exude serum. Scars of scalds are much thinner than those of deep burns and cause less contraction and disfigurement. Blisters have an hyperaemic zone around them. There is a reddening and swelling of the papillae in the floor of the blister. The blister fluid contains white and red cells. A post-mortem blister does not show hyperaemia in the surrounding area and the floor is not red. If inflammable fluids are used, signs of trickling of the burning fluid will be present on some parts of the body, e.g. if kerosene is splashed on a body lying on its back and then ignited, runs of burning liquid will be seen on the sides of the neck, sides of the trunk, between the thighs, etc. Inhalation of steam may cause thermal injury of the respiratory tract, producing death by asphyxia due to obstruction to airway by the oedematous mucous membrane. Death usually occurs from shock, fluid and electrolyte disturbance and secondary infection.

Occurrence: Scalds are usually accidental due to bursting of hot water bottles, bursting of boilers, splashing of fluid from cooking utensils, or pulling over saucepans or kettles by children, etc. Occasionally, children suck the spouts of kettles, which causes severe steam scalds of the mouth and air-passages with oedema of the glottis. Suicide by scalding is rare. Boiling water ma be thrown with intent to injure. Murder scalding is rare.

Spontaneous combustion: Spontaneous combustion of the human body not occur. A body can never be consumed without the application of fire or flame and it cannot be reduced to ashes without the surrounding objects being set on fire.

Preternatural Combustion: This is very rare. During putrefaction, inflammable gases are produced in abdomen due to the action of microorganisms upon organic matter. These gases are ignited if a flame is nearby, and cause partial burning of the neighbouring soft tissues, but complete combustion of the body does not take place. It is not a valid scientific phenomenon.

During life, inflammable gases, such as hydrogen, hydrogen sulphide and methane may be formed in the alimentary tract. Such gases when belched or let off from the anus, may be ignited on the application of a flame and cause a burn at the site.