14.7 Thermal Injuries Flashcards
Hypothermia
General
Factors involved
Presentation
Consequences and PM findings
- Can still happen in temperate climates (ie severely cold conditions not necessary)
- At risk- elderly and very young (infants)
- reversible (warm pt up)
Factors involved:
- Low environmental temperature
- Age and physique
- Thyroid function (hypothyroidism with dysregulation of temperature
- Lack of adequate food and clothing (eg vagrants)
Presentation
- Paroxysmal undressing can be found at scene
- Based on core temperature (rectal)
• 32-37°C- Subjective feeling of cold, shivering, vasoconstriction
• 24-32°C- Decreased LOC, bradycardia, hypotension, can lead to death here
• <26°C- Recovery here is rare
Hyperthermia types
1. Benign” conditions
- Heat cramps
• Excessive sweating with electrolyte loss and subsequent cramping of voluntary muscles
- Heat exhaustion
• Sudden collapse due to dehydration and loss of electrolytes
• Equilibrium re-established after a few minutes with cooling down and replacement of fluids
2. Heat stroke (Malignant condition)
- High temperatures and humidity (athletes, military personnel, children)
- Rectal temperatures >41°C, thermoregulatory mechanisms fail
- Patient is dry and hot to touch with flushed/pale skin, peripheral blood pooling
- muscles are breaking down
- Consequences include:
• Rhabdomyolysis due to muscle necrosis
• Disseminated intravascular coagulation
• Cardiac arrhythmias
3. Malignant hyperthermia
- Anaesthetic related condition associated with usage of suxamethonium or inhalation agents
- Genetic predisposition
- Very high temperatures and muscle rigidity
Thermal injury (heat)
Can be due to:
- Defect in regulation of body temperature
- External application of heat»_space;> factors
➡️The applied temperature (>44 degrees Celsius)
➡️Conduction ability of body surfaces (e.g. presence of clothes)
➡️Time period of application
Severity of burn injury
- Specific to individual cases
- Four factors influence this:
➡️Extent of area affected (TBSA : “RULE OF NINES”)
➡️Severity of burns (different classifications)
➡️The victim’s age
➡️Presence of inhalation injuries
How to you measure the extent of burn
- TBSA (Total body surface area %)
- RULE OF NINES
• Clinical classification
• 30-50% TBSA is seen as fatal
• Age dependent (Older people die at lesser percentage) - Children have different scoring system because of big head
Severity of heat classification
Wilson’s (newer): depth of tissue damage
- 1st degree: erythema and blistering without loss of the dermis. Heat causes capillary dilatation and transudation of fluid into tissues=swelling. Blister formation due to epidermal split (erythematous base, fluid center, pale skin cap), <1cm blister resorbs, >1cm bursts. Blister can form from within the thickness of the epidermis to the epidermal-dermal junction. Heals without scarring.
- 2nd degree: Full thickness destruction with coagulated/charred epidermis and central necrosis, surrounded by 1st degree burns and/or hyperaemia. Eventual sloughing of central necrosis occurs with and epithelial growth from the margins. If epithelial structures survives epithelialization can occur from islands within the burnt tissue. Heals with scarring (puckering and distortion of skin surface occurs due to contraction)
- 3rd degree: destruction and loss of tissue below the skin, any severity (subcutaneous>muscle>bone). Can actually be less dangerous to life if confined to a small area when compared to a larger area of superficial burns.
NB Systemic complications of burns
Toxaemia
- Death usually occurs within 24 hours due to absorption of denatured tissues (death due to extensive burn injuries)
Electrolyte disturbances
- 24-48hrs: Hypernatremia and hypokalemia
- >48hrs: Hyponatremia and hyperkalemia
Infections/Septicaemia
- Multi-organ failure secondary to septicaemia is the main cause of death in these cases
- Source of infection can start in the necrotic tissue or the lungs (esp if intubated, ventilated and immobile).
- Organisms are virulent and opportunistic.
- Involved organisms can include: Gram negative (Klebsiella, Eschericia, Proteus), Clostridia (C. perfringens, C. tetani), Pseudomonas, Staphylococci and fungi (Candida)
Lungs
- Bronchopneumonia: could be ventilator associated and a source of sepsis, at autopsy
lungs are heavy due to consolidation and brittle.
- Adult Respiratory Distress Syndrome
Thrombo-embolism
- Develop due to long periods of immobilization in these cases
- Sudden death can be due to pulmonary embolism (large saddle embolus)
Stress ulcers in the GIT
- Described by Curling in 1842 (acute peptic ulcers following burn wounds).
- Similar ulcers also occur in sepsis and cases of multiple injuries.
- Mostly found in the pre-pyloric part of the stomach and the distal part of the duodenum, but can occur anywhere in the GIT.
- Can be single or multiple
- Early changes can be noted in the stomach mucosa within 24hrs.
- Tend to haemorrhage (mortality >50%)
- Perforation in chronic ulcers> peritonitis
Shock
- Presents with all the manifestation of the shocked patient.
- Also a specific classification for burn victims: Burn shock
- Burn shock: not only due to fluid depletion with loss of intravascular volume but also due to loss of proteins
Inhalation injuries
- Acute laryngospasm can occur (irritation by heat/chemicals)>prevents deeper injuries.
- Secondary severe systemic infections and Adult Respiratory Distress Syndrome are very common after inhalation injuries.
Other systemic complications of burns
- Acute tubular necrosis
- Disseminating intravascular coagulation
- Fat embolism
- Hepatocellular necrosis
- Natural diseases not associated with burn injuries
Moist thermal damage (scalds)
- Due to hot liquids (usually water), but can also be caused by oils, steam, rubber, molten metals and chemicals.
- Does not cause charring, carbonization or singeing of surface hairs like dry heat does.
- Resembles a first degree dry burn with reddening, desquamation and blistering but differs in
shape (sharply demarcated edge corresponding to the limits of contact with the hot liquid). - Examples: immersion in a hot bath causes horizontal edge with some irregularity due to splashing, splashing or tipping causes trickle pattern (gravity) and posture can be estimated with the worst affected areas representing the point of contact.
- Children: accidental injuries (pulled on themselves) burnt areas are the face, neck, chest and arms with spared areas in the axillae and back.
- The red base may be covered by macerated, wrinkled epidermis and later the scalded skin might swell and exude serum.
- Superimposed infection of the burns may occur but when extensive damage exists the cause of death can be due to the effects of shock, electrolyte and fluid disturbance or chest infections.
- Severity depends on the temperature of the liquid, duration of skin contact and presence of clothing.
Electrical injury
- Current (measured in Ampère)(A):
- Strength and type can cause differences in injury
- Strength of current-
• 30mA-upper level of tolerance, 40mA- loss of consciousness, 100mA- fatal - Type of current-
• AC/DC- body 4-6 times more sensitive to AC than DC
• DC- batteries, defibrillators, AC- household, hold-on effect
