HEAT EXHAUSTION / STROKE Presented by –Capt Manish Khandare RMO, 1STC Chairperson – Lt Col P V Padman Cl spl (Med)

HEAT EXHAUSTION / STROKE

Presented by –Capt Manish Khandare RMO , 1STC

Chairperson – Lt Col P V Padman Cl spl (Med)

HIGH TEMP. + HIGH HUMIDITY + PHYSICAL WORK = HEAT ILLNESS.

When the body is unable to cool itself through sweating , serious heat illness may occur.

The most severe heat induced illnesses are heat exhaustion and heat stroke . If left untreated heat exhaustion could progress to heat stroke and possible death.

Normally the body temperature undergoes a regular circadian fluctuation of about 0.6*C being lowest in the morning and highest in the evening.

Body temperature is controlled by the hypothalamus.

Preoptic anterior and posterior hypothalamus receives two kinds of signals

1 – from peripheral nerves – reflects warmth / cold receptors.2 -- from the temperature of the blood bathing the regions.

Thermoregulatory center of the hypothalamus integrates these signals to maintain normal temperature.

A normal body temperature is ordinarily maintained , despite environmental variations , because the hypothalamic thermoregulatory center balances the excess heat production derived from metabolic activity in muscle and the liver with heat dissipation from the skin and the lungs.

The mean oral temperature is 36.8*+/-0.4*C ( 98.2*+/-0.7*F).

Heat disordersCirculatory instability

Heat syncope Heat edema

Heat induced skin disorders

Prickly heat (milaria rubra)

Water and electrolyte imbalance

Heat cramps Water depletion heat exhaustion Salt depletion heat exhaustion

Hyperthermic failure of thermoregulation

Heat stroke

Heat syncope

Orthostatic dizziness and fatigue Precipitated by prolonged standing Maybe a prelude to more serious heat effects due to

peripheral vascular pooling Collapse of venomotor tone

Heat oedema

Unacclimatized people in tropics due to cutaneous vasodilatation Venous stasis Expansion of ECF space

HEAT CRAMPS:

MUSCLE SPASMS USUALLY 1 TO 3 minsMAY RECUR UPTO SEVERAL HOURSDUE TO : MILD WATER INTOXICATION SALT DEPLETION

PRICKLY HEAT:PRICKLY HEAT:

ACUTE OR CHRONIC BLOCKAGE OF SWEAT DUCTS DUE TO ACUTE OR CHRONIC BLOCKAGE OF SWEAT DUCTS DUE TO MACERATION OF STRATUM CORNEUM.MACERATION OF STRATUM CORNEUM.

Manifests as erythematous , pruritic ,maculopapular rash.Manifests as erythematous , pruritic ,maculopapular rash.

Core temperature is less than 40*C (104*F)

No evidence of CNS dysfunction though some patients may be anxious or irritable.

HEAT EXHAUSTIONCLINICAL FEATURESincreased thirstweaknessfatiguefrontal headacheimpaired judgmentvertigonausea, vomitingmuscle crampsincreased core temp upto 40 degrees C (104 degree F )

Move patient to a cold room.

Remove clothes.

Cold sponging with cold water

Replacement of fluids and electrolytes.

HEAT STROKE

Triad of - hyperpyrexia (core body temperature >41.1*C /106*F )

- CNS dysfunction (delirium, convulsions or

coma)

- Hot dry skin

Heat stroke

Classic heat stroke: exposure to high

environmental temp in sedentary persons.

Exertional heat stroke: from strenuous physical

exercise in hot climate in healthy persons.

Non exertional heat stroke: Alcohol ,

MAOIs,amphetamines and by illicit use of

phencyclidine , lysergic acid diethylamide

(LSD).

Pathogenesis

Heat stroke: a syndrome of

multi organ dysfunction in which

encephalopathy is a dominant

feature.

Pathogenesis (contd)

Multi organ dysfunction is due to:

direct cytotoxic effects of heat

Inflammatory response of host

Direct cytotoxic effects of heat

Direct tissue injury: body temp 41.6-42oC (105*F-107*F) for 45 min to 8 hours

Attenuated heat shock response: decreased production of heat shock proteins (stress proteins)

PATHOGENESIS – HEAT STROKEHeatHeat

GIT(Gut ischaemia)Leakage of EndotoxinsMonocytes

Acute phaseresponse

TNF AlphaI L-1, 6, 10Endothelial cell activation

-- Interferes with thermoregulation-- Activation of coagulation-- Alters vascular-tone

Multi organfailure

Clinical manifestations

Hyperthermia and CNS dysfunction are the essential criteria for diagnosis

Hyperthermia: core temp -41*C (106*F)Hot dry man: absence of sweating

CNS dysfunction:Inappropriate behaviour, confusion, impaired

cognition, psychosis or coma

Clinical manifestationsTemperature – 106*F

Pulse – approx 130 beats /min is common

Blood pressure – usually hypotensive.

CNS – delirium , confusions ,delusions ,convulsions , coma.

Eye – may reveal nystagmus , pupils may be pinpoint or normal.

Clinical manifestations… GIT manifestations:

Diarrhoea, vomiting, GI hemorrhage, hepatic injury

Myocardial injury:Nonspecific ST-T changes on ECGElevated CK-MB enzyme

Renal – Acute Renal Failure is a common complication

37*C ( 98.6*F) – Normal body temperature.

38*C (100.4*F) – Sweating , feeling uncomfortable .

39*C (102.2*F) – Severe sweating , tachycardia and breathlessness.

40*C (104*F) – Fainting , dehydration , weakness , vomiting , headache ,dizziness , confusion , hallucination , delirium and drowsiness.

41*C (105.8*F) – condition worsens , palpitations may occur.

42*C (107.6*F) – May be comatosed , severe delirium , convulsions , tachycardia.

1. Complete blood count – elevated levels of WBCs as high as 40,000 /cu mm have been reported.

2. Serum electrolytes– hypokalaemia , hypocalcaemia and hypophosphataemia.

3. Blood sugar estimation – hypoglycemia usually seen.

4. Renal function tests – Elevation in serum uric acid levels , blood urea nitrogen , serum creatinine are common.

5. Hepatic function tests – Aminotransferases (AST/ALT) commonly rises in the early phases of heat stroke.

6. Cerebrospinal fluid analysis – CSF may show nonspecific pleocytosis , CSF proteins level may get elevated as high as 150mg/dl.

7. Muscle function test – Creatinine Kinase (CK) , Lactate dehydrogenase ( LDH ) , aldolase , and myoglobin are commonly released due to muscle necrosis. CK levels may exceed upto 100000 IU/ml.

Management

Principles

Rapid cooling of body

Support of failing organ systems

Heat stroke is an Medical emergency.Rapid reduction of core body temperature is the cornerstone of treatment.

Cooling of body

Two methods1. Ice water immersion

2. Evaporative cooling

Ice water immersionAdvantages:

Faster coolingNo sophisticated equipment

Disadvantages:

Vasoconstriction of skin vesselsCoronary spasmUncomfortable to patient

Evaporative coolingDone by spraying warm water over body and

blowing air

Advantages:No vasoconstriction of skin vessels

DisadvantageSlower cooling

i.v fluids initially 4 units of Normal saline in 1 hourfollowed by Ringer Lactate / D5%.

Inj. Paracetamol .1amp. IM stat.

Muscle relaxants such as Benzodiazepines and neuroleptic agents such as chlorpromazines used to inhibit shivering and as prophylaxis for seizures.

PREVENTION OF HEAT RELATED

ILLNESSES

ACCLIMATISATION2 WeeksShort periods of work every day to beginDuration and frequency lengthened after a

weekConstant vigilance during the processSevere tests of endurance avoided

Training

Always in consultation with med authPreferable in morning hrs

Clothing

Wear light , loose clothing ,made of wicking fibers. These fibers have tiny channels that wick the moisture from your skin to the outer layer of the clothing where it can evaporate more easily.

THANK YOU