Deaths caused by abnormal temperatures
These injuries may be due to exposure to cold (hypothermia),
high environmental temperatures (hyperthermia) or hot objects coming into
contact with the body (burns). All these deaths are unnatural.
Hypothermia or low body temperature is defined
as a condition where the central or core body temperature is 35 8C or lower.
Hypothermia is a common complication where individuals are exposed to low
environmental temperatures. This often occurs amongst mountaineers and other
adventurers exposed to the environment. Although the environmental temperature
as such plays an important role, it is also important to remember that movement
of air (wind) lowers the temperature even further (wind factor).
Exposure to cold water, for instance after
shipwrecks, increases the risk of hypothermia. Should an intoxicated person
fall into cold water, hypothermia will be worse, as alcohol causes
vasodilatation, which increases heat loss (see study unit 11).
The elderly and the young are at greatest risk
to develop hypothermia in the domestic situation.
Within certain temperature ranges, hypothermia
has a protective effect on certain vital organs, like the brain, as it
decreases the energy needs (including oxygen) of the organs. This is one of the
reasons why the body temperature is usually lowered during open-heart surgery
to protect the brain. Cooling down and rewarming of the body in these
circumstances are of course strictly controlled to prevent complications.
Local changes due to hypothermia include
frostbite, which can lead to loss of fingers, toes or even parts of the face.
The post-mortem findings are often nonspecific.
Typically the hypostasis has a pink to rose-pink discoloration. It tends to be
present over the extensor surfaces and large joints. Pulmonary oedema, acute
gastric erosions and acute pancreatitis as well as perivascular haemorrhages
and small micro-infarcts (small foci of necrosis) may also be present.
Hypothermia can cause confusion and irrational
behaviour; sufferers can even take off their clothes due to a false perception
that it is hot. This then creates the impression that the person was assaulted
or even raped. These people often hide away from sight, the so-called
``hide-and-die'' syndrome.
Hyperthermia is a condition which occurs when
the internal body temperature rises above 40,5 8C, and is usually seen in the
following two situations:
Exposure to high environmental temperatures. In mines the temperature and humidity are often
very high. Physical activity in these circumstances may cause hyperthermia in
individuals who have not acclimatised beforehand. It can be aggravated by
drugs, that cause constriction of the blood vessels in the skin, for instance
drugs that decrease mucus secretion during a common cold (eg ephedrine). The
capacity for giving off heat is lost and the patient can become ``overheated''.
The post-mortem findings are often nonspecific,
with signs of heart failure (ie pulmonary oedema), internal haemorrhages due to
clotting abnormalities, and renal failure.
Malignant hyperthermia. This condition occurs in individuals who are genetically susceptible to
certain anaesthetic agents, especially if halothane is used in conjunction with
a muscle relaxant (succinylcholine). Professor Harrison of the University of
Cape Town developed an antidote, Dantrolene, years ago. This resulted in a
significant drop in the mortality rate. In addition to the high body
temperature the patient develops an increased potassium level and other
metabolic abnormalities. Microscopic examination of the muscles shows myopathy
(muscle abnormality) with a moth-eaten appearance and with the nuclei located
centrally in the cells.
Strictly speaking frostbite is also a form of
thermal injury, but it was discussed under hypothermic injuries. This
discussion will therefore focus on the injuries resulting from the application
of local heat to the body.
Burns are a common problem in South Africa
because the majority of the population use open fires for the preparation of
food and heating. As was said in the study unit on carbon monoxide poisoning,
these open fires in enclosed spaces are a major cause of death due to the
production of carbon monoxide.
Deaths due to thermal injuries can be
instantaneous or almost immediate if severe, or can occur later due to
complications, for instance infection. The inhalation of smoke and toxic
substances found in smoke can also cause death from damage to the airways (heat
inhalation syndrome). This may even occur without any external thermal injuries
to the body.
Old people and children are especially
susceptible to thermal injuries. In elderly people the skin is less sensitive,
and they do not realise in time that they are in contact with a hot object. For
example hotwater bottles often cause burns. Children sometimes pull containers
with boiling water over themselves, as they are inquisitive and cannot see what
is happening on the stove.
Deaths due to burns may thus be an accident, a
homicide or a suicide.
A post-mortem examination of a severely charred
body is often difficult as it might be almost impossible to identify the
person.
An important factor to be determined is whether
the person was alive at the time the fire started, or whether he or she was
already dead at that time (sometimes fires are started to conceal a murder).
These aspects will be discussed later.
Classification of thermal wounds
Burn wounds are classified according to depth
First degree
- only the epidermis is involved
- often
painful
- sunburn a possible cause
- heal
without scar tissue formation
Second degree
- the
epidermis and part of the dermis are involved
- sometimes blisters may be present on the skin
- painful
- heal
without scar tissue formation, except
when complicated by infection
Third degree
- the
epidermis and the full thickness of the dermis are involved
- usually painless due to the destruction of the
nerve-end fibres in the skin
- heal
with scar tissue formation
Some authors describe fourth-degree burns as
charring of part of the body.
Skin burns may further be graded according to
the percentage of skin surface involved. In certain areas, for instance the
face and perineum (genital region) there is a high risk of complications.
·
Local complications. The most important is sepsis due to infection of
the open wounds containing dead (necrotic) tissue. Over the flexor aspects of
joints, for instance the elbow and knee, fibrosis forms scars, which can cause
loss of movement. This is also known as a contracture.
·
Systemic complications. This is usually the result of fluid and
electrolyte loss through the raw and injured surface of the skin. In addition
lung complications can occur due to inhalation of hot air. Pulmonary
thrombo-emboli due to immobilisation of the patient, and stasis, may also occur.
The post-mortem findings will depend on the
degree of charring. In cases where charring did not occur, open, raw areas are
seen. The pathologist must give an estimate of the percentage of the body
surface damaged by the burns. In third-degree burns physicians often make
incisions in the skin to release the tension of the contracted skin on the
underlying soft tissue (escharotomies). This must not be confused with incised
wounds.
With inhalation injuries the airways will show
signs of damage, and the lungs will be congested in the initial stages. Signs
of diffuse alveolar damage or shock lung will be found at a later stage.
In cases of charring the body will be in the
so-called pugilistic or boxer stance (see study unit 3) due to shortening of
the muscles as the proteins break down and coagulate as result of the heat. The
flexor muscles have a larger mass and are therefore stronger than the extensor
muscles. The flexor muscles will therefore dominate if all the muscles are
shortened. The elbows and knees will bend and the body will assume the stance
of a boxer.
The skull bone can fracture and a bloody fluid
can ``cook up'' from the bone into the extradural space. This is known as
extradural burn haematoma. It must not be confused with injuries of the skull
and extradural haemorrhage due to trauma in the ante-mortem period. The skin
and soft tissue can also tear, due to shortening of muscles (heat tears). This
is not an indication of ante-mortem injuries.
If a body is totally charred, X-rays for
identification purposes as well as to locate possible projectiles and other
injuries are mandatory. Examination of the teeth is also indicated for
identification purposes. In aircraft accidents charring is a common problem and
correct identification often depends on dental records (forensic odontology).
The following signs could indicate whether the
person was alive when the fire started:
·
the carbon monoxide in the body (by determining the carboxyhaemoglo-bin
level [COHB]): a level of more than 5% in a nonsmoker and more than 10% in a
smoker indicates that the person was alive when the fire started
·
ash and soot in the airways, stomach and oesophagus
·
fat emboli in the pulmonary vessels (only indicated by some authors)
Boiling water and other hot liquids often cause
scald wounds in children. These wounds are characterised by the fact that the
intensity of the scalding decreases as the fluid runs over the body and cools.
The presence of clothes may also influence the extent and distribution of scald
wounds caused by boiling water.
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