Heat Related Illness Richard Dionne MD - PowerPoint Presentation

Slide1

Heat Related Illness

Richard Dionne MDEmergency Medicine – University of OttawaMarch 2013

Slide2

Heat Related Illness

Goals & ObjectivesDiscuss the thermoregulation differences between hyperthermic

entities and fever

Discuss the differences between Heat Exhaustion and Heat Stroke and their target organ injuries

Identify the differential diagnosis and the proper investigation in the ER

Discuss the acute management in the ER

Slide3

Basics

Severe illness secondary to overwhelming heat stressDehydration – electrolytes – thermoregulation dysfunction – MOF

Increase temperature – increase O2 consumption and metabolism

Failure of

Oxydative

Phosphorylation

and certain enzymes > 42 °C

Slide4

Classification

1

-

Hyperthermic

Diseases

A -

Minor

Cramps / Edema / Syncope / Prickly HeatB - MajorHeat ExhaustionHeat Stroke2- Hyperthermic EntitiesA - Malignant HyperthermiaB - Neuroleptic Malignant Syndrome 3- Febrile Illnesses

Slide5

Hyperthermia

«

Auto-Regulation

»

Peripherical

& Central Thermistors

Central Thermostat(Anterior Hypothalamus)Modulation ResponsePeripherical Adaptation Mechanism(vasodilation & sweating)

Slide6

Hyperthermia

vs Fever

Hyperthermia

…

T

hermoregulatory

mecanism are surpassed … Peripherical mechanism dont suffice, The Hypothalamic « set point » is normal …Fever… Cytokins reaches Anterior Hypothalamus Resets the Thermostat... new

«

set point

»

Peripherical mechanism are intact...

Slide7

Heat Exhaustion

Core T < 40° CFluid & electrolyte depletionThermoregulation is maintained

CNS function is preserved

Slide8

Heat Stroke

Core T > 40.5 CLoss of thermoregulation, severe CNS dysfunction & MOFTriad:

Hyperthemia

/ CNS /

Anhydrose

Classic

Exertional

Slide9

Heat Stroke

Classic Heat Stroke (non-exertional)Compromised thermoregulation

(cannot remove from source)

Days

Severe dehydration

Warm & dry skin

Slide10

Heat Stroke

Exertional Heat StrokeYounger / athletic with combined environmental &

exertional

heat stress

Internal heat production overwhelms dissipating mechanisms…

Sweating may be present at beginning

Slide11

Heat Cramps

Secondary to excessive sweating and sodium lossCramps in heavily exercised musclesPrimarily in lower extremitiesDuring or after exercise

Slide12

Prickly Heat

Blockage of sweat glands leading to a maculopapular rash over clothed area …

Slide13

Heat Edema

Swelling of dependent areas of body (usually lower limbs)Resolves with acclimatization & rest

Slide14

Etiology

Pre-existing conditions:Age extremes Dehydration

Cardiovascular disease

Obesity

Hyperthyroidism

Febrile Illness

Skin disease that interferes with sweating (psoriasis / eczema)

Slide15

Etiology

Pharmacologic:Sympathomimetics

LSD / PCP

MAO inhibitors

Anticholinergics

Antihistamines

B-blockers

Diuretics

Drug & alcohol withdrawal

Slide16

Etiology

Physical / Environmental:Prolonged exertionLack of mobility

Lack of air conditioning

Excessive humidity

Lack of acclimatization

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Heat

Exhaustion

«

labs

»

Possibly normal



Hematocrit

 / natremiaHypoglycemia ? BUN / CreatinineConcentrated urine

Slide18

Imaging

ECG: cardiac risksCT-scan Head: r/o CNS primaryChest X-ray: ARDS?

Slide19

Differential

Diagnosis

Sepsis

Meningitis

Malaria

Thyroid storm

Status Epilepticus

Cerebral Hemorrhage

Malignant HyperthermiaNeuroleptic malignant syndromeTetanusToxicologyASA / PCP / stimulants / Anticholinergic

Slide20

Heat

Stroke

Classical

Exertionnal

predisposing

factors healthyolder youngersedentary exerciseanhidrosis

diaphoresis

heat

wave

sporadic

mild

CPK



rhabdomyolysis

mild

coagulopathy

DIC

mild

acidosis

marked

lactic

acidosis

oliguria

acute

renal

failure

Slide21

Treatment

Slide22

Heat

Exhaustion

«

Treatment

»

Rest

/

Shade

/ Cooling methodsRehydration … PO … 0,1% NaCl solution IV … 0,9% NS ( modest to avoid overhydration)Peds 20 cc/KgShivering & seizures:

Benzos

Danger : Sodium

levels

Slide23

Cooling measures

EvaporativeVery effectiveSpray with fine mist

Airflow with fans

Prevent shivering

Conductive

Ice pack groin /

axilla

& neck

Immersion not practical ad risk if seizures“Stop cooling at 39°C to risk hypothermia!”

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«

Mecca

Body

Cooling

Unit

»

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Not

this way ?

Slide26

Heat

Stroke

« Complications »

Rhabdomyolysis & Renal Failure

Hypoglycemia /

 Na

/

 K /  CaSevere Hepatocellular damage AST/ALT can be in the 1000 ’s < 24hCoagulopathy / DIC / hemorrhageRefractory Hypotension

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Bad

Prognosis

Coagulopathy

Lactic Acidosis (classical)

T° > 42.2°C & prolonged hyperthermia

Prolonged coma > 4 hrs

Hypotension

Acute Renal Failure

HyperkalemiaAST > 1000 U/L

Slide28

Hyperthermia

Hepatic

Clotting

Fibrinolysis

Endothelial

Megakaryocyte damage factors damage damage Depletion DIC Thrombolysis Thrombocytopenia clotting factorsHemorrhage

Slide29

Hypotension



CVP &



CVP &



CVP &  Cardiac Output  Cardiac Output  Cardiac Output

Hypovolemic

Hypodynamic

Hyperdynamic

Fluids

Fluids

&

Pressors

Cooling

&

fluids

NS 250-500 cc

then

slowly

(

rarely

)

modest

300 cc/h NS

correct BP > 90/60 or CVP N

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Prevention

1-

Rely

not on

thirst

2- Drink on

schedule

3-

Favor sports drinks4- Monitor weight5- Watch urine6- No caffeine or alcohol7- Key on meals8- Stay cool when you can

Slide31

Summary

Slide32

Malignant

Hyperthermia

Autosomal

Dominant condition

Severe

muscular

hypermetabolism produced by excessive release of calcium from sarcoplasmic reticulum in response to anesthetic agents …TreatmentDantrolene : 1-2 mg/Kg IV q 6h (max 10mg/Kg/24h) calcium release from sarcoplasmic reticulum

Slide33

Neuroleptic

Malignant Syndrome

Dopamine

receptor

blocade

at

Corpus Striatum Muscular Spasticity & Dystonia Heat ProductionTarget Organs (rhabdomyolysis, etc)Treatment : Dantrolene

Bromocriptine (Dopamine

Agonist

)

Slide34

Points to

remember ...

In

doubt

treat

as

«

Heat Stroke »ASA & Acetaminophen = no placeDantrolene & Steroids = no placeKeep away from : Levophed (alpha-adrenergics)vasoconstriction & no benefit to cardiac output

Atropine (

anticholinergics

)

inhibition of

sweating

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Remember

«

Heat

stroke

victims

should

be cooled as rapidly as possible. The more rapid the cooling, the lower the mortality. »« It

does

not

take

long to

either

boil

an

egg

or to

cook

neurons

. »

D Hamilton

Slide36

Heat Related Illness

Key ConceptsAntipyretics are ineffective and should not be usedDiaphoresis is common in

exertional

heat stroke

Rapid (convective) cooling should be initiated rapidly

Heatstroke can cause right-sided cardiac dilation and elevated CVP, resembling Pulmonary Edema, but requires crystalloid resuscitation

Slide37

Questions ?