Hypo & Hyper thermia
Transcript of Hypo & Hyper thermia
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Hypo & Hyper Thermia
Dr. Mohammed Saleh Madadin
Forensic Medicine
College of Medicine – university of
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Thermal Injuries
Exposure To cold
Exposure to
Heat
Generaleffects
Localeffects General
effectsLocaleffects
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Definitions
Thermal Death
Internal Heat
Enviromental Heat
Heat Load ( gain)
Heat Loss
1 C = 33.8 F
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Heat loss and Heat gain
Heat is gained:
by conduction from warm air surrounding the body
by the body’s metabolic activity ( liver & muscles)
Heat is lost:
by conduction and radiation to cold air (or water)
by evaporation of sweat from the body surface
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Mechanism Of regulation of
body Temp.Whenever the heat load exceeds the heatloss body heat rise and body start loss heat
How body decrease temp:
1-vasodilation of bl.v due to inh. Of symp.centre in post.hypothalamus
2-sweating
3- decrease heat production ( inhibitchemical thermogenesis)
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How body increase temp .?
1- V.C due to stim. Of post.hypothalamus
2- piloerection due to stim. Of sympathetic sys.
3- increase heat production by promoting shivering
Internal heat maintained despiteenviromental variations bythermoregulatory mech.
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nerves
Less heat generated
More water covers theskin.
More evaporation
Skin arteries dilateMore blood to the
skin.More radiation &conduction of heat
Muscles of
skin arteriolewalls relaxSweatglands
increasesecretion
Musclesreduceactivity
Core bodytemperature
>37°C
Hypothalamus
Thermoreceptors
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nerves
More heat
generated
Less water covers theskin.
Less evaporation
Skin arteriesconstrict
Less blood to theskin.
Less radiation &
conduction of heat
Muscles of
skin arteriolewallsconstrict
Sweatglands
decreasesecretion
Musclesshivering
nerves
Core bodytemperature
<37°C
Thermoreceptors
Hypothalamus
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Hyperthermia
Systemic hyperthermia
Endogenous \ Febrile hyperthermia
Exogenous\ non-febrile hypothermiaHeat Cramps
Heat Exhaustion ( Heat prostration)
Heat Syncope ( Heat collapse)
Malignant hyperthermia
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Heat Stroke
Increase in body temp. above 41C inpresence of environmental heat.
ability to cool the body can no longercompensate for the heat load
life-threatening conditionhot, dry skin, altered sensorium,tachycardia, hypotension ,
hyperventilation
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Predisposing Factors:
alcoholism, dehydration, obesity,preexisting disease (cardiac and
neurological), diuretics and majortranquilizers such asphenothiazines,tricyclic antidepressants,and monoamine oxidase inhibitors ,sympathomimitic e.g cocain and amphet..Relative humidity , DM
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Obese individuals show a greatersusceptibility to heat stroke ….. Why ?
This is due to :(1) Increased adipose tissue creates
an greater demand on the heart
(2) the fat provides extra insulationfor the body, preventing loss of heat
(3) since metabolic heat is produced
in proportion to the bulk of the tissue
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Heat stroke is generally seen in twosettings
1- that involving relatively youngindividuals exposed to high
temperatures while undergoingextreme exertion — military recruitsand football players in training
2- a prolonged heat wave. In this lattercircumstance affected individuals are
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also occur in children left unattendedin automobiles for long periods of timein the summer
Symptoms of heat stroke may come on
suddenly or be preceded by prodromicsymptoms — nausea, vomiting,vertigo, muscle cramps, dyspnea, afeeling of warmth.
increase in heart rate Paresthesias
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Complication:
If lives short time after acute insult :
PneumoniaTub. Necrosis of kidney
adrenal Hmg
hepatic necrosis
myocardial fiber necrosis &
subendocardia HMG
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If the diagnosis of heat stroke has not
been made prior to death, thediagnosis is often circumstantial basedon history, exclusion of other causes of death
If an individual’s time of death is
known and if a rectal temperaturetaken shortly thereafter showshyperthermia, a diagnosis of heatstroke can be made
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Cause of death in hyperthermia
Cardiac dyasarrythmia and collapse
seizures
Shock
Autopsy finding:not specific
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Heat acclimatization
tolerance to exercise in heat
Due to Subsequent to repeated bouts
of exercise in a hot environment The 1ry benefit evident as a reductionof the incidence or severity of symptoms of heat illness, andincreased work output concurrent withreduced cardiovascular, thermal, andmetabolic strain.
in metabolic biochemical
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Saunas
Exposure to hot & dry environment
60- 120 C
10 – 30 min.
Core Temp begin to rise 1-3 min. ,constant increase rate
Once outside temp back to normal (
30 min.)
Sweating the only way to cooling
Pt with severe heart dis. At risk
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Hypothermia
In the past, injury and death from theeffects of low temperature wasthought to occur almost exclusively
among those subjected to extremes of climate out of doors.
Now, generally appreciated that
hypothermia was a common andwidespread danger in temperateclimates and indoors.
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Case
In Germany , December 2002 , mancalled a police , reporting he found hisdisabled GirlFriend lying dead on the
living room Floor.
She lives alone
DecemberDisabledLive alone
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Either :
1- General2-Localized
Dry or in water
Considered hypothermia when templess 35C
External parts of body : enviromentalDependentInternal part : constant temp. ( core
Temp.)
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Case
In December 2002 , man called apolice , reporting he found his disabledGirlFriend lying dead on the living
room Floor.
She lives alone , last time seen last 2days
Crime scene Inv.:
The floor was flooded with water
The ambient temp. was 19C
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Loss of heat in water faster than in air
The aged and the infants are mostvulnerable
Very high mortality of hypothermia in firstfew weeks of life ( relation of surface areato mass and heat regulation centreimmature)
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Pathophysiology of hypothermia
Internal temp. regulated by
- Heat production :metabolism , muscular activity
- Heat loss :
increasing blood flow through skin or
sweating
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Brown fat play role in chemicalthermogenesis by increase rate of metabolism
in children heat production up to 100%while in adult no brown fat ( 10-15%heat production)
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Circumstances of hypothermia :
- exogenous : environmental (less 10C)
- Endogenous : dis. Of endocrine glands ,drugs (barb. , diazepam) , mental dis.
- Other :
Age and physiqueSocial and financial factors
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LOW ENVIRONMENTALTEMPERATURE:
Critical temp. of air to maintain eqili.
25 CNo specific figure , depend on otherfactors
10 C consider to be danger to causehypothermia
External winds will worse the effect
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HYPOTHYROIDISM
Myxoedema , women , over 70
DrugsImipramine , chlorpromazine ,diazepam , barb.,alcohol
clothing
Women tolerate cold better due tothick layer of s.c fat
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Alcohol tend to aggravate the loweringof body temp rather than rising ( theheat generated by alcohol is due
internal combustion which thereforelowers the temperature of inner core of the body)
Cutaneous diltation of peripheralvessels (loss of heat and warm flush
feeling)
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Alcohol have a secondary effectcausing incapacity and immobility.
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Mechanism of death
As temp. falls decrease indissociation of oxyheamoglobin lesssupply of O2 to tissue (most affected
nervous tissue)
utilizing capacity of tissue is reducedat lower temp., all these depress the
oxidative process in the tissue andleading to tissue hypoxia
Therefore the immediate cause of
death is circulatory failure
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Clinical Manifestation
36°C -32°C: feeling of being cold,shivering and constriction of bloodvessels
32°C -24C :dulling of consciousness, afall in respiration and heart rate, and alowering of blood pressure
Loss of reflexes , cold necrosis ,
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Hypothermia can causeheamoconcentration by:
1- cold diuresis (15C) trigger diuresis
2-leaking of plasma into ECF ( coldedema)
Hyperglycemia :caused by action of glucocorticoid , and epinephrine on liver
which resultant depletion of glycogen.
Case
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CaseIn December 2002 , man called a police , reporting he foundhis disabled GirlFriend lying dead on the living room Floor.
She lives alone , last time seen last 2 days
Crime scene Inv.:
The floor was flooded with water
The ambient temp. was 19CWomen rectal temp. was 16 C
The tap water temp was 16 CAutopsy :Rigor fully developedHypostasis pinkFrost erythema on her kneesMultiple erosion spots on
gastric mucosa
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Autopsy
There may be no signs at autopsy
history may be all-important
If pt admitted to hospital and 'warmed-up', death may supervene at any timeup to a few days later.
signs of hypothermia: patches of pinkto brownish pink discoloration may beseen
The color of hypostasis cherry red or
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extremities may be cyanosed or theymay be white
Sometimes the feet are blue to theankles, above which is pale.
Oedema may be seen
blistering of the skinSigns of pre-existing disease
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Lesions with hypothermia
ACUTE GASTRICEROSIONS(Wischnevsky’s Gastriclesion):
The stomach mucosa have numerousshallow ulcers, the floor of eachcontaining a dark brown plug of alteredblood
the stomach contents sometimescontain dark acid-affected blood.
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PULMONARY OEDEMA: common butnot specific
PENVASCULAR HAEMORRHAGES:
in the brain, especially in the walls of the third ventricle, they are notparticularly specific
Microinfarcts are common in manyorgans in hypothermia.
Case
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CaseIn December 2002 , man called a police , reporting he found his disabledGirlFriend lying dead on the living room Floor.
She lives alone , last time seen last 2 daysCrime scene Inv.:
The floor was flooded with water
The ambient temp. was 19C
Women rectal temp. was 16 C
The tap water temp was 16 C
Autopsy :Rigor fully developedHypostasis pinkFrost erythema on her kneesMultiple erosion spots on gastric mucosa
Toxicology And Histology
toxicology : -veHistology : Wischnevsky’s spots
Diagnosis Made as Fatal
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THE 'HIDE-AND-DIE'SYNDROMEAlso called terminal burrowingbehavior
In some cases of hypothermic death inthat it is associated with the victimundressing and hiding away from sight
The signs of hypothermia are usuallypresent
problem then arises as to whether thevictim became hypothermic first,which led to mental confusion that
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Paradoxical undressing
Perimortem act in wich the victimremoves his clothing
Due to
- Terminal hallucination
- Physiologically when failure of V.C
lead to warm blood flow back to theskin lead to burning sensation
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Biochemical markers of hypothermia
catecholamines appear in the bloodand then urine in the early stages, butthen decline, as the adrenals becomeexhausted.
- There is a variation in theadrenaline:noradrenaline ratio, allthese changes being manifestations of
stress induced by low temperature
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Hypothermia in Water
70-90 min. to die if immersed in water4-9C and in 30 min at 0 C
Critical temp. of water to maintaineqili. 35 C
Thickness of individual S.C fat is mostimp. Factor
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Cause of Death
Sudden cooling of the skin const. of bl.v reflex stim. Of heart incr. blpressure and C.O Sudden increase inwork of Lt vent Vent. fibrillation (bothatrial and vent. Ectopic beat common
during 1st few min. of cold imerssion)reflex disturbance of breathing:involuntary Controlled breathig lead to
inhl. Of water
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Post immersion Death
Occur following rescue from cold water
Conc. When taken out
Because of continuous drop of temp.for period of time even if rewarmed
Cause of death : cardiac arrest
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LOCAL INJURY DUE TO COLD
There are a number of different clinicallesions caused by the effect of
prolonged cold on the extremities.
1- 'Immersion foot' and 'trench foot'
refer to damp cold damage lead tonecrosis and gangren
- ' '
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Case # 2
In Japan , a morning in January, amale in his early sixties was founddead in an outdoor parking area.
The minimum temperature during thenight before he was found dead wasestimated to be 4.0°C.
Autopsy revealed the pinkness of hypostasis, slight abrasions andbruises on the face and the
extremities, collapse of the lungs, and
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Expalanation
Hyperacetonemia : occurin hypothermia
Ubiquitin: one of the
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