Heat Illness/Hyperthermia
Victor Politi, M.D., FACP
Medical Director –
St. Johns University-Physician
Assistant Program
Risk factors for heat illness
Obesity
Fatigue
Drugs
Alcohol
Sunburn
Unacclimatized
Fluid deficit
Previous history of heat injury
Many medical conditions
Febrile illness
Cystic fibrosis
Diabetes
Malnutrition
Heat Illness Classification
• Heat Rash
• Heat syncope
• Heat cramps
• Heat exhaustion
• Heat stroke
Minor Heat Illness Heat Cramps
• Brief, intermittent, often severe muscular cramps
typically occurring in muscles that are fatigued by
heavy work
• Usually occur after exertion
• Copious hypotonic fluid replacement during
exertion
Minor Heat Illness Heat Cramps
• Related to salt deficiency
• Victims exhibit -hyponatremia,
hypochloremia, low urinary sodium and
chloride levels
• Usually rapidly relieved by salt solutions
Minor Heat Illness
Heat Syncope
• Individuals at risk should be warned to
move frequently, flex leg muscles
repeatedly whenever standing
• Scintillating scotomata, tunnel vision,
vertigo, nausea, diaphoresis, and weakness
are prodromal symptoms of syncope
• Adequate oral volume replacement may
prevent some conditions
Minor Heat Illness - Prickly Heat
AKA miliaria rubra, lichen tropicus, heat rash
• Acute phase – Produces intensely pruritic vesicles on an
erythematous base
– Rash confined to clothed areas
– Effected area completely anhydrotic
• – may persist for weeks
– chronic dermatitis -frequent complication
Heat Exhaustion - two types classically
described
– Water depletion heat exhaustion
• inadequate fluid replacement by persons in heat “
voluntary dehydration”
• weakness, fatigue, frontal headache, impaired
judgement, vertigo, nausea/vomiting, occasional
muscle cramps,sweating, body temperature near
normal
• orthostatic dizziness/syncope may occur
• results in progressive hypovolemia
• Untreated can progress to heat stroke
Heat Exhaustion - two types classically
described
• Salt depletion heat exhaustion
– takes longer to develop than water depletion
form
– systemic symptoms occur
– hyponatremia, hypochloremia, low urinary
sodium and chloride concentrations
– Symptoms similar to water depletion type, body
temperature remains near normal
Heat Exhaustion: Diagnosis
• Vague malaise, fatigue, headache
• Core temperature often normal; if elevated less
than 1040F
• Mental function essentially intact; no coma or
seizures
• Tachycardia, orthostatic hypotension, clinical
dehydration (may occur)
• Other major illness ruled out
• If in doubt, --- treat as heat stroke !!
Heat Exhaustion - Treatment
• Rest
• cool environment
• Assess volume status (orthostatic changes,
BUN, hematocrit, serum sodium)
• Fluid replacement
• Consider admission if patient is elderly, has
significant electolyte abnormalities or
would be at risk of recurrence if d/c
Hyperthermia
A patient presents to the ED with elevated
body temperature 1st thought ??
? Infectious etiologies/severe infection
but some patients with elevated temperature,
including some with extreme pyrexia, do
not have fever at all, they have
hyperthermia !
Fever versus Hyperthermia
• Body temperature can become elevated
through either of two very different
processes
• In fever, thermoregulation remains intact
while hyperthermia represents
thermoregulation failure
Causes of HyperthermiaDisorders of excessive heat production
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Exertional hyperthermia
Heatstroke
Malignant hyperthermia of anesthesia
Neuroleptic malignant syndrome
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Thyrotoxicosis / Pheochromocytoma
Salicylate intoxication / Delirium tremens
Cocaine, amphetamines, other drugs of abuse
Status epilepticus /Generalized tetanus
Hyperthermia
Splanchnic
vasoconstriction
Thermal injury
Rhabdomyolysis
Disseminated intravascular
coagulation
Diminished
renal blood flow
Glomerular
damage
Myoglobinuria
Hyperuricemia &
urinary acidification
Renal Failure
A catastrophic life-threatening medical
emergency ---
HEAT STROKE
Heat Stroke Diagnosis
• Exposure to heat stress, endogenous or
exogenous
• Signs of severe CNS dysfunction (coma,
seizures, delirium
• Core temperature usually 410C (105.80F) or
more,
• Dry, hot skin frequent,
• Marked elevation of hepatic transaminases
Classic Heatstroke
• Occurs primarily in epidemics during
summer heat waves
• Most likely to effect the elderly and patients
with serious underlying illnesses
• Infants also at risk
• Typical victim confined at home w/no fan
or A/C
• Dehydration - predisposing factor
Classic Heatstroke
• Other risk factors - obesity, neurologic or
cardiovascular disease, use of diuretics,
neuroleptics, or medications with
anticholinergic properties that interfere with
sweating
• Alcohol use may be a risk factor
Exertional Heat Stroke
• Like classic heat stroke- occurs during
hot,humid weather
• Occurs sporadically - effecting young,
healthy persons engaged in strenuous
physical activity
Initial Treatment of Heat
Stroke
• Immediate cooling
• Protect airway (intubate if comatose or
seizing)
• IV line with 0.9% NaCl or Ringer’s lactate
• CVP or Swan Ganz catheter in hypotensive
patients
• Foley catheter; monitor output
Initial Treatment of Heat
Stroke
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Rectal probe - monitor temperature
Oxygen, 5-10L/min
ABGs
Labs - CBC, electrolytes, BUN, glucose, SGOT,
LDH, CPK, calcium phosphate, lactate, PT/PTT,
fibrin degradation products
• Check glucose by dextrostix method & treateadminister D50 if hypoglycemia present
Cooling Modalities to lower body
temperature in heat stroke
• Ice-water immersion
• Evaporative cooling using large circulating fans
and skin wetting
• Ice packs
• Peritoneal lavage
• Rectal lavage
• Gastric lavage
• Cardiopulmonary bypass
• Alcohol sponge baths (caution)
• Phenothiazines (caution)
Treatment of early complications of
Heat Stroke
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Shivering
Convulsions
Myoglobinuria
Acidosis
Hypokalemia
Hypocalcemia
Heat Illness Prevention
• A Crucial issue
• Counsel persons with any risk factors
regarding symptoms of heat stroke
– Elderly persons
– persons with chronic diseases
– those on medications predisposing them to heat
illness
Heat Illness Prevention
• Exertional heat stroke is most likely to
strike young, healthy persons involved in
strenuous physical activity
– many of these people have risk factors for heat
illness -commonly obesity,diarrhea,febrile
illness
– other variables to consider- hydration,salt
intake, clothing, and climatic conditions
Heat Illness Prevention
• Fluid intake is the most critical variable
Questions ?