Medicine - heat, electricity and cold

Question 1

Heat - local effects - burns

Answer 1

o Dry – BURNS
 Severity
* 1st degree – reddening and blistering
* 2nd degree – destruction of skin
* 3rd degree – destruction of soft tissue
 Extent
* Rule of nines – used to estimate how much fluid needs to be given to replace fluid lost from burns

Question 2

Heat - local effects - scald

Answer 2

 Liquid > 55 degrees
 Similar to burns but no charring
 Reddening; blistering
 Fluid levels
 Effect of clothing
* Clothing stuck to skin and holds hot fluid against the skin making scold worse – could cause pattern in the scold
 Children

Question 3

Importance of burns/scalds

Answer 3

 Accidental vs Inflicted vs Negligent
 Can be serious and sometimes fatal injuries
 Children (old people)
* Dependant individuals – often happens when only one other there, in private with no other witnesses
 Common issues include
* Causation
o Accident vs Inflicted vs negligent
* Time Needed
o > 60 degrees – few seconds only
o > 44 degrees – over several hours
o Time halves with each degree
o Normal body temp is 37 degree C

Question 4

Heat - systemic effects - direct effect

Answer 4

o Direct – Hyperthermia
 Heat exhaustion
 Heat stroke

Question 5

Heat - systemic effect - indirect effects - FIRE

Answer 5

• Very Variable (heat, smoke, explosion)
• Causes of death
  o Smoke inhalation (carbon dioxide poisoning)
  o Heat and flame
  o Fluid loss (from burns)
  o Infection (of burns or pneumonia)

Question 6

Heat - systemic effect - indirect effects - SMOKE

Answer 6

• Carbon monoxide
  o House Fire -> 0.5-2% CO in air
  o Car exhaust fumes -> 5% CO
  o CO + Hb -> COHb
   Carboxyhaemoglobin – carbon monoxide binds to haemoglobin meaning oxygen can no longer bind
  o CO poisoning causes the blood to change colour

Question 7

Medicolegal issues of fire/CO

Answer 7

• Medico-Legal Issues
  o Cause of death
  o Negligence (CO Poisoning)

Question 8

Electrical injury - local effects

Answer 8

o Burns – usually enters through fingers and out through feet
o Other lesions
 Blister
 Spark Burn

Question 9

Electrical injury - systemic effects

Answer 9

Electrocution
Usually cardiac arrest
Most important factor – current
A = V/R
Other Factors
Time current passes
Route of current
10mA – pain and twitching
30mA – muscle spasm
50mA – cardiac arrest
AC > DC -> arrhythmia
More resistance, means less current passes through body
Thick dry skin – resistance of 1,000,000 ohms
Wet skin – resistance of 1,000 ohms
Mode of death
Ventricular fibrillation (respiratory paralysis)

Question 10

Electrical injuries - Lightning

Answer 10

o Duration – 0.001 seconds
o Current – 10-200,000 amps
o 1/3 people killed
o Effects
 Electrocution
 Burns
 Explosion
* Ears
* Eyes
* Unconscious

Question 11

Medicolegal issues of electrical injuries

Answer 11

o Establishing the diagnosis
 Difficult or impossible
 May only have only tiny burn on finger on post-mortem so hard to establish facts – must look at surrounding circumstances instead

Question 12

Hypothermia - local effects

Answer 12

o Frost bite – tissue killed by cold

Question 13

Hypothermia - systemic effects (causes, age, maintenance of body temperature, post-mortem findings)

Answer 13

o Systemic hypothermia – core body temperature 35 degree or below
o Causes
 Exposure to cold
* Dry
* Wet – e.g. falling in river - conduct heat away much more quickly
 Alcohol/Drugs
* May wear less clothing
* Effects people’s behaviour
 Natural Disease
* Underactive thyroid makes more susceptible to hypothermia

o Age
 Young infants
 Young adults
* Largely due to alcohol and misbehaviour
 The old
* Often economic reasons – not putting heating on
* Could be from medical issues

o Maintenance of body temperature
 Controlled by the brain
* Vasoconstriction in skin and muscles – body shuts down supply of blood to skin or muscles keeping warm blood in centre of body supplying organs such as heart, brain
* Shivering
o Not something you can control – muscles contracting to generate heat

o Post-Mortem Findings
 Red patches on trunk and limbs
 Acute pancreatitis – inflammation from shut off of blood supply
 Gastric ulceration/haemorrhage
 No findings

Question 14

Medicoloegal issues in hypothermia

Answer 14

o Misdiagnosis of death
 Person may appear to look dead but actually are not
o Negligence
 Not wrapping baby up etc
o Making the diagnosis at PM
o Bizarre behaviour
 Paradoxical undressing