Chapter 21: Effects of Cold and Heat

21.1: Introduction

• Thermal injury — defined as an injury to the body %%resulting from localized or generalized exposure to extremes of temperature%% due to various etiological factors.
• Heat load is the %%sum of heat generated by the oxidation of metabolic products%% and heat acquired from the environment around. It has three mechanisms:
  • Conduction
  • Radiation
  • Evaporation
• Heat loss by evaporation has further two more mechanisms.
  • Insensible heat loss – this is due to the %%continued diffusion of water molecules%% through the skin and respiratory surfaces regardless of the body temperature.
  • Heat loss by sweating: In cold weather, the sweating is essentially zero, while in hot weather it is maximum.

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21.2: Hypothermia

• Hypothermia — when an individual’s body temperature is below 95°F (35°C). This will occur when the %%loss of body heat exceeds heat production%%.
• Trench Foot — due to exposure to cold (5-8 C) %%coupled with dampness and there will be no tissue freezing%%.
• Frostnip and Frostbite — due to exposure to cold below 2.5-0°C. Here there will be tissue freezing.
  • Frostnip: The skin %%turns white and waxy or gray in color and mottled%%, but feels normal to touch.
  • Frostbite follows then when no treatment is given at the initial phase of frostnip. Ice crystals are then formed in the skin and deeper tissues, which can exert osmotic force, causing water to move from intercellular space.
• Exposure to low temperature: the most common incidence of hypothermia.
  • Frostbite commonly occurs in soldiers in winter warfare hiding in the trenches or in a shipwreck in Antarctic waters, etc.

Factors Modifying Effects of Cold

• Adults are able to bear cold better than very young and old. Children have a high body surface-to-weight ratio and lose heat rapidly.
• The longer the duration of exposure, the more severe are the effects due to the evaporation of body heat.
• Fatigue, exhaustion, intoxication, and starvation hasten the effects of cold.
• Degree of thyroid deficiency, even clinical myxoedema, which predisposes to low body temperature, may predispose to hypothermia.
• Taking phenothiazine drugs also predisposes to hypothermia.

Pathophysiology of Cold

When a healthy person is exposed to extreme cold, the following changes may occur and they are:

• Reduction of heart rate and respiration.
• Impairment of tissue respiration due to failure of dissociation of oxygen from hemoglobin, resulting in tissue anoxia.
• Lowering of body metabolism.
• Slowing of body enzymatic process.
• Fall of body temperature resulting in cessation of vital functions.
• Vascular response of the body to excessive cold includes.

Frost Bite

• Frostbite — a %%syndrome complex comprising of local tissue necrosis%%.
• It commonly occurs in soldiers in winter warfare hiding in the trenches or in a shipwreck in Antarctic waters, etc.
• Causes: Vasospasm; Paralysis of vasomotor control of blood vessels.

Clinical Findings

• Skin will be ice-cold, showing erythematous patches on distal and exposed parts such as ear, nose, fingers, and toes.
• Generalized muscular stiffness.
• Feeble pulse and low heart rate with low blood pressure.
• Depressed reflexes.
• Lethargy feels heavy, and drowsiness.
• Stupor, delirium, coma, and death are gradually due to a reduction in oxygen supply to tissue, due to its inability to dissociate from oxyhemoglobin.

Treatment

• Gradual restoration of body warmth by putting the victim on a warm bed, hot water fomentation, hot coffee or tea, and stimulants like — digitalis, alcohol, strychnine, etc. orally.
• Warm saline may also be given intravenously.

21.3: Hyperthermia

• Hyperthermia — an acute condition that occurs when the %%body produces or absorbs more heat than it can dissipate%%. It is usually due to excessive exposure to heat.

• Body temperatures above 40°C (104°F) are life-threatening. This compares to the normal body temperature of 36-37°C (97-98°F).

• At 41°C (106°F), brain death begins, and at 45°C (113°F) death is nearly certain.

• Internal temperatures above 50°C (122°F) will cause rigidity in the muscles and certainly, immediate death.

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• Trauma and death from hyperthermia or heat is due to the exposure to heat, derived from:

  • Natural sources such as the heat derived from the sun
  • Artificial sources such as industrial furnaces, huge baking ovens, etc.
  • Poorly ventilated or closed rooms or a factory wherein the temperature is high and the air is moist.

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• Three conditions may result due to high environmental temperature:

  • Heat cramps — no rise in body temperature.
  • Heat prostration — subnormal body temperature.
  • Heat hyperpyrexia — rectal temperature above 41 degrees.

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• The following factors are considered predisposing to the effects of hyperthermia:

  • Malnourishment
  • Overexertion
  • Fatigue
  • Chronic alcoholism, hunger, lack of sleep, etc.
  • Mental depression.

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Signs and Symptoms

• Heat prostration/heat exhaustion is characterized by mental confusion, muscle cramps, and often nausea or vomiting.

• Victims may become confused, may become hostile, often experience headaches, and may seem intoxicated.

• Blood pressure may drop significantly from dehydration, leading to possible fainting or dizziness, especially if the victim stands suddenly.

• Heart rate and respiration rate will increase (tachycardia and tachypnoea) as blood pressure drops and the heart attempts to supply enough oxygen to the body.

• The skin will become red as blood vessels dilate in an attempt to increase heat dissipation.

• The decrease in blood pressure will cause blood vessels to contract as heat stroke progresses, resulting in pale or bluish skin color.

• Eventually, as body organs begin to fail, unconsciousness and coma will result.

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Clinical Manifestations

• Heat cramps: The victim here complains of severe painful spasms in the voluntary muscles of the body %%due to excessive perspiration and loss of body electrolytes%%.

• Heat Exhaustion:

  • Prostration
  • Peripheral vascular collapse
  • Pallor (due to poor venous return)
  • Hypotension (due to poor venous return)
  • Flushing of the face, throbbing temples, scanty perspiration
  • Collapse

• Heat stroke — it is due to the %%impairment of the heat regulation mechanism in the body%%, especially resulting in the death of the victim due to the paralysis of medullary centers.

  • An acute form with sudden onset without any prodromal symptoms.
  • A gradual onset forms with definite prodromal symptoms.

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Treatment

1. First Aid
   • Heat stroke is a medical emergency requiring hospitalization, and the local emergency system should be activated as soon as possible.
   • The body temperature must be lowered immediately.
   • Both passive and active cooling is helpful.
2. Passive Cooling: The victim should be moved to a cool area (indoors, or at least in the shade) and clothing removed to promote heat loss (passive cooling).
3. Active Cooling
   • The person is bathed in cool water, a hyperthermia vest can be applied, or the person may be wrapped in a cool wet towel.
   • Cold compresses to the torso, head, neck, and groin will help cool the victim. A fan may be used to aid in the evaporation of water.
   • The use of ice and very cold water may lead to hypothermia; hence they should be used only when there are means to monitor the victim’s temperature continuously.
   • Immersing a victim in a bathtub of cold water (immersion method) is a recognized method of cooling.
4. Hydration
   • Hydration is of paramount importance in cooling the victim. This is achieved by drinking water. Commercial isotonic drinks may be used as a substitute. Alcohol and caffeine should be avoided due to their diuretic properties.
   • The victim’s condition should be reassessed and stabilized by trained medical personnel.
   • The victim’s heart rate and breathing should be monitored, and CPR may be necessary if the victim goes into cardiac arrest.
   • The victim should be placed into the recovery position to ensure that their airway remains open.
5. Prevention
   • Avoid overheating and dehydration.
   • Light, loose-fitting clothing will allow perspiration to evaporate.
   • Wide-brimmed hats in bright colors keep the sun from warming the head and neck; vents on a hat will allow perspiration to cool the head.
   • Avoid strenuous exercise during daylight hours in hot weather.
   • Be aware of humidity in presence of direct sunlight which causes the heat index to be 10°C (18°F) hotter than the atmospheric temperature shown in the thermometer.
   • Persons in hot weather need to drink plenty of liquids to replace fluids lost by sweating.
6. Susceptible Populations
   • Heat illness most seriously affects the poor, urban dwellers, young children, those with chronic physical and mental illnesses, substance abusers, the elderly, and people who engage in excessive physical activity under harsh conditions.

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21.4: Scalds

• Scalds — trauma resulting from the application of moist heat commonly involving only superficial layers of the skin.

• Moist heat is generated in the following forms:

  • Hot water or oil or any liquid at or near boiling point.
  • Superheated industrial steam.

• Clinically scalding is classified into three degrees:

  1. Erythema: This is the reddening of the skin which appears at once as the moist heat is applied.
  2. Vesication: Also called blister formation is chiefly due to increased capillary permeability, and this needs a few minutes to develop.
  3. Necrosis of dermis: This results when deeper layers of skin are involved.

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Medicolegal Importance

• Usually scalds are accidental due to splashing or pouring of fluids while cooking or bathing, etc.
• The accident is common in children or in elderly.
• Boiling water may be thrown with malicious intent.
• Deliberate scalding by hot water is common in child abuse.
• Suicide and homicide by scalding is extremely rare.
• Scalding could be either antemortem or postmortem.

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21.5: Death Due to Fire

• Deaths due to fire or burns usually result from the application of dry heat to the body.
• Incidences of burns could be due to building catching fire, clothes are worn catching fire, inflammable liquid fire explosions, industrial furnace burns, etc.
• Superficial Burns: These burns are usually red, moist, and very painful. The outermost layer of the skin is involved (the epidermis) and there may be blisters present.

Effects of Burns

• Scarring is usually more with burns due to dry heat. It would be present in cases involving the dermis. Burns involving only epidermis will heal without scar formation.
• Keloid formation is more common with corrosive burns.
• Curling’s ulcer is a rare sequel of severe burns, seen in the duodenum. It is due to tissue hypoxia and capillary endothelial damage.

Factors Modifying Effect of Burns

• The higher the intensity the more severe will be the effects.
• The more the duration, the more severe will be the effects.
• The depth of burn injuries is particularly important especially if the burn is causing decreased oxygen supply to the end digits of the body or difficulties with chest expansion and breathing.

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Thickness Burns

• Mid-dermal:

  • The outermost layer of skin is lost, as well as parts of the dermis (the next layer of skin).
  • The burn is pink in color, with small white patches.
  • The skin still blanches on pressure and is painful.
  • Healing occurs in 7-14 days depending on the degree of skin destruction.

• Deep-dermal burns:

  • Here there is deeper dermal destruction.
  • The burn appears white and does not blanched on pressure.
  • The skin is less sensitive and takes a longer period of time of heal, with scarring.

• Full-thickness burns — extend deep down into the dermis. The burn is leathery, ranges in color from white/grey/black, and is non-painful.

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Causes of Death Burns

• Death Occurring within Few Hours
  • Victim may die due to shock, coma and asphyxia. Each of these is discussed individually below:
  • Shock:
    • Primary (neurogenic) due to fear, severe pain, injury to, vital organs leading to death within 24 to 48 hours
    • Secondary (vascular) due to loss of serum from burnt area — developing depletion of blood volume and hypovolemic shock, leading to death within 24 to 48 hours.
  • Coma due to congestion of the brain and serious effusion into ventricles.
  • Asphyxia causes suffocation due to the inhalation of smoke or gasps of combustion.
• Death Occurring within Few Days
  • Inflammation of Internal Organs: These are inflammation leading to meningitis, peritonitis, pneumonia, bronchitis, pleurisy, enteritis, and Curling’s ulcer in the duodenum.
  • Gangrene: Complications connected with the ulcers produced by burn such as gangrene, erysipelas, tetanus, profuse hemorrhage on separation of the slough, etc.
  • Exhaustion due to severe pain and dehydration from loss of fluid.
  • Septic absorption from excessive suppuration. Suppurative case death may occur within 5 to 6 weeks or even after a long time.
  • Toxemia occurs due to the absorption of histamine formed as a result of the combustion of tissue.
  • Hepatorenal Syndrome: In every case of burns of any severity, absorption of altered protein occurs and this in turn leads to cellular damage to the liver and kidneys.

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Postmortem Appearances of Burns

External Appearances

• Clothing should be removed carefully and examined for the presence of kerosene, petrol, and other such inflammable and combustible substances.

• Any other articles such as keys, metallic rings, ornaments, etc., worn on the body should be removed and preserved. It may be useful in establishing identity.

• Face is usually distorted, swollen with tongue protruded out.

• Findings observed vary according to the nature of the substance used to produce burns:

  • Radiant heat-whitish
  • Explosions in coal mines or by gun-powder—blackening and tattooing of the parts.
  • Kerosene oil burns: characteristic odor and sooty blackening of the parts.
  • Degloving/destocking may be seen due to cuticular peeling

• The hair undergo a peculiar effect of heat called singeing.

• Pugilistic attitude — It is a condition wherein the body assumes a rigid position with the limbs flexed and resembles a boxer in defending position.

• Cracks and fissures resembling incised wounds may be seen in line with blood vessels exposed through them.

• Charring of the body depends on the degree of postmortem burns or burning of the body after death.

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Internal Appearances

• Skull bones may be fractured and burst open due to intense heat, along the skull sutures
• Brain and meninges
  • Congested
  • Blood is usually extravasated.
  • The brain is sometimes shrunken.
• The larynx, trachea, and bronchial tubes contain carbon and soot particles, and the mucosa is congested with frothy mucous secretions.
• Pleura is congested and inflamed with serous effusion.
• Lungs is congested and edematous.
• Heart is chamber full of blood, cherry red in color due to inhalation of carbon monoxide.
• Stomach may contain carbon-impregnated mucous membrane. It may be red.
• Spleen may be enlarged and softened.
• Liver is cloudy swellings and necrosis of the cells if death is delayed.
• Kidneys show signs of nephritis.

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