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Forensic medicine > Thermal, Electrical and Lightning Injuries > Flashcards

Thermal, Electrical and Lightning Injuries Flashcards

1
Q

Different types of physical burns

A

Flames, Radiating, Steam and Heated liquids

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2
Q

What is a physical burn?

A

The application of a thermal force on the body

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3
Q

What are the classificationsfor thermal burns?

A

The depth of the skin injury, the extent of body surface area and the type of injury (e.g., a flame burn)

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4
Q

1st degree burn

A

not classified, fiery red hot and very painful but not blistered

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5
Q

2nd degree burn

A

Partial thickness. Extend though the epidermis to the dermis of the skin. healing occurs by regeneration: full function and appearance is fully recovered

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6
Q

3rd degree burn

A

Full thickness. Extends though the dermis and may penetrate the subcutaneous tissue. hair follicles, sebaceous and sweat gland are irreversibly damaged and destroyed. healing occurs through scar formation and re-epithelialization.

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7
Q

4th degree burn

A

Complete burn.Extend into the subcutaneous gland to the muscle, fascia and bone. They may generate systemic toxic rxns or rapidly lead to infection or sepsis

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8
Q

What other factors affect the appearance and extent of injury?

A

Length of exposure and Degree of heat applied.

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9
Q

What is Scalding?

A

Thermal burn from heated liquids or steam

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10
Q

Common occurrences in Scalding

A

1st and 2nd degree burns
common in children
no singeing of hair
no charring of the skin
presence of clothing produces a more severe injury due to heat retention.

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11
Q

Typical occurrences in Flame burn and Radiant heat

A

Partial and Complete thickness burns
Depending on the severity of the injury, all cutaneous variety of injury can be seen : charring, singeing and blistering
Destruction of Identifying features
Typically observed in shack fire victims
Smoke inhalation and airway trauma

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12
Q

Autopsy of Burn victim

A

Establish ID
Determine COD and wheher victim was alive or dead when burnt
Recognize and ID heat artefacts
Collect evidence

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13
Q

Establish ID for Burn victim

A

External examination
X-ray (prosthsis, bullet and weapons etc)
Teeth for forensic odontology
Personal stigmata- tattoos, scars and deformities
Clothing
Fingerprints
Internal organ and internal Surgical artefacts e.g presence of uterus to sex the victim

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14
Q

Determine COD, was victim alive or not?

A

CO levels less than 10% indicative of death before burn
Evidence of smoke inhalation
Fat embolism and antemortem injuries

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15
Q

Unusual Autopsy Artefacts?

A
  1. burn Extradural hemorrhage:
    - mimics antemortem BFT to head
    - excessive heat causes brain shrinkage
    -perforating blood vessels stretched and ruptured
  2. Heat fractures
    Charred bone may fracture d/t intense heat
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16
Q

Special investigations in a Burn Autopsy

A

BAC level
CO level (<10% saturation)
DNA
HISTOLOGY(MICROSCOPY): evidence of smoke inhalation and fat embolism
TOXI – drug essays (blood and vitreous humor)

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17
Q

Thermo-regulation

A

Body temperature tightly controlled by CNS to prevent changes in body core temperature.

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18
Q

Hyperthermia

A

Excessive heat absorption and production

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19
Q

Hypothermia

A

Excessive heat loss and impaired heat production

20
Q

Temperature Control

A
  1. Accumulation vs Dissipation(mainly through evaporation through sweat mechanism and vasodilation)
  2. Heat source (endogenous-metabolic breakdown of lipids and sugar and exogenous –environmental temperature)
21
Q

Factors affecting Temp Control

A
  1. Temperature diffs between environment and the body
  2. Pre-existing pathology
  3. Age and physical size
  4. Integrity of the skin
  5. Air movements
  6. Moisture content of surrounding air
  7. Amount of sub-cutaneous fat present
  8. Physical activity/exertion
  9. Clothing
  10. Acclimatization and physical fitness
22
Q

Hyperthermic Syndromes

A
  1. Heat Stroke
  2. Malignant Hyperthermia
  3. malignant Hyperthermia of Anaesthesia
23
Q

Heat Stroke risk factors

A
  • Occupational heat exposure and sun exposure
  • underlying fever or use of pyrogenic drugs such as stimulants with physical exertion of body
  • increased incidence amongst alcoholics
24
Q

Heat Stroke Features

A
  1. Total breakdown of thermoregulatory mechanisms
  2. Medical emergency
  3. Core body temp >40.5 degrees Celsius
  4. lack of sweating with warm dry skin with Kussmal’s type of breathing
  5. CNS features: irritability and aggressiveness, delirium, stupor and coma
25
Q

Malignant Hyperthemia definition

A

Acute hypercatabolic state with upward loop of increasing body temperature and loss of thermo-regulatory control

26
Q

Malignant Hyperthemia factors

A
  1. High environmental temp
  2. High environemtal humidity
  3. Excessive physical exertion (e.g. endurance athletes)
27
Q

Malignant Hyperthermia of Anaesthesia definition

A

Acute hypercatabolic state with upward loop of increasing body temperature and loss of thermo-regulatory control

28
Q

Malignant Hyperthemia features

A
  1. Drug induced in genetically predisposed persons
  2. Genetically predetermined
  3. Mechanism of Death: uncoupling of oxidative phosphorylation with massive energy release and core body temp over 42 degrees Celsius
  4. Commonly implicated drug agents: halothane and succinylcholine
29
Q

Autopsy findings in Malignant Hyperthemia of Anaesthesia

A

CNS: Cerebral oedema, Congestion, disintegration and reduction of Purkinje layers
Lungs: pulmonary oedema with frothy hemorrhagic sputum
Heart: subendorcardial hemorrhage, right atrial dilation and epicardial hemorrhage
Liver: Centrilobular necrosis
Musculoskeletal: rhabdomyolysis
Renal: acute kidney injury

30
Q

Hypothermia definition

A

Core body temp below 35 degrees Celsius
Occurs when the heat production is insufficient to maintain core body temperature within normal physiological parameters.

31
Q

Hypothermia Pre-disposing factors

A
  1. exposure to cold environment
  2. Under influence of drugs or alcohol and exposed to the cold
  3. Accidental (locked in freezer)
  4. Hypothermic operative procedures
  5. Elderly and infants
  6. Inappropriately dressed for cold environment
32
Q

Predisposing factors of hypothermia

A
  1. Age
  2. Physique
  3. Hypothyroidism
  4. lack of adequate clothing, food and indoor heating
  5. Nutritional status - undernourished at risk d/t low fuel reserves and poor insulation to thin layer of fat pad
33
Q

Pathophysiological changes in Hypothermia

A
  1. Pulse rate slows down
  2. Initial BP increase, followed by subsequent fall
  3. Capillary constriction
  4. Initial rise in respiratory rate, with gradual decrease until complete cessation
  5. Cerebral blood flow and O2 supply finish rapidly
  6. at < 32, CNS depression, sensory loss, hallucinations, LOC and hypothermic anesthesia
  7. Atrial fibrillation, terminal ventricular fibrillation and progressive bradycardia
  8. Peripheral and pupil reflex diminish pogressively
  9. Microthrombi and embolus formation; paralytic ileus; diuresis
34
Q

Autopsy findings in Hypothermia

A

Non-specific:
extensor lividity,
peripheral cyanosis,
generalized oedema,
pulmonary oedema
congestive heart failure

Specific:
gastric erosions
acute pancreatitis
CNS perivascular hemorrhage 3rd ventricle)
mico-infarcts, frostbite and gangrene
pneumonia

35
Q

Electrocution definition

A

passing of an electrical current through the body, causing disruption to Cardiac, Respiratory and Neurological function

  • may or may not be fatal
    -physical marks found in 1/3 cases (herpen et al)
  • circumstantial evidence is CRITICAL e.g. recent thunderstorm, died while operating electrical machinery
36
Q

Outcomes of electrocution: Variables in current

A

Variables in current (Amperage, Voltage and Direction):

Voltage: low voltage may be more lethal than high- inducing potential fatal cardiac arrythmias

Amperage (amt of current flowing) more lethal than voltage e.g. high tension wires and heavy duty appliances

Direction (AC/DC)
AC 4x more lethal than DC
causes severe contractions as muscles and nerves more sensitive to frequencies > 10 000 Hz

37
Q

Variables in Contact

A

Resistance(insulation):
-clothing
-moisture on skin cause clothing to be blast off

Pathway and area: Passes through heart and/or CNS

Duration: prolonged contact will increase RISK OF ARRYTHMIA

38
Q

Electrical Marks

A
  1. Variable in appearance
  2. Depressed areas may be stained (brown, black or greenish) d/t to the carbonization of material from the conductor
  3. Areas surrounding the marks raised from contraction and peripheral oedema
  4. Skin erythema may be present
  5. Shape of mark often corresponds to the contact surface
  6. High amperage has an explosive effect and may produce injuies resembling BULLETS AND STABS/INCISED WOUNDS
  7. Balls of molten metal may be carried deep into the tissue
39
Q

Lightning Injuries

A
  1. Diffs in action potential in -ve and +ve charged particles of the atmosphere
  2. 100 strikes every second on earth
  3. 300KV wit 1-10 Billion joules of energy
  4. 1/3000 lifetime risk
  5. 70-90% victims survive as most energy is absorbed by the ground
40
Q

Direct or Indirect Strike consist of

A
  1. Blast waves
  2. Ignition of objects and clothing
  3. Electrical injuries to the body
41
Q

Blast Wave features

A
  1. 5kg TNT force with rapid extension of surrounding air at 50 m/sec
  2. Two types of Injuries:
    • rupture o damage to ear drum
    • blunt force impact-type injuries
    • penetrating injuries from PROPELLED shrapnel
42
Q

Ignition of Objects and Clothing

A

27 000C (5x hotter than sun)
1. flame burns from environment and clothing
2. contact burns from jewelry and metallic clothing items
3. magnetization of metallic objects
4. penetrating injuries from EXPLODING shrapnel

43
Q

Electrical- type injuries: Direct or Indirect strike?

A

DIRECT strike may instantly vaporize the body. May also coagulate the body mostly pass harmlessly through the body to the ground.

INDIRECT strike passes a massive current from the ground through the lower limbs of the body causes SYSTEMIC NEUROLOGICAL DAMAGE. may strike many individuals at once.

44
Q

Lightning injuries commonly observed

A

ELECTRICAL TYPE INJURIES
1. Cardiovascular: cardiac arrest (asystole) and fatal arrythmia
2. Fatal seizures/convulsions
3. Fatal direct brain injury
4. fatal spinal cord damage

LATE SEQUELAE(LONG TERM EFFECTS CHRONIC EFFECTS)
1. Cardiovascular: angina pectoris (months) and myocardial necrosis (days to weeks)
2. Chronic seizures/convulsions
3. Direct Brain Injury: Parkinson-like syndromes and High incidence of depression and suicide
4. Spinal cord damage: partial paralysis and focal neurological deficits

45
Q

Physical features in Lightning injuries

A
  1. body may not present any injuries and evidence of strike is often circumstantial
  2. metallic objects become magnetized
  3. arborescent dendritic or leaf like figure on skin - Lichtenberg marks
  4. Burns may appear as zig zag lines.
  5. lightning marks may simulate gunshot like perforations on skin
  6. clothing may ignite
46
Q

Lichtenberg marks

A
  • d/t rupture of dermal blood vessels along subcutaneous electrical path
  • arborescent dendritic or leaf like figure on skin
  • burns may appear as zig zag lines
47
Q

Clothing artefacts

A
  • Moisture on skin may be vaporized causing clothimng to blast off. victims are sometimes found nake w/o othr physical injuries.
  • body hair may be singed(melted), and clothing magnetized

Forensic medicine (2 decks)

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