Heat Illness/Hyperthermia

Victor Politi, M.D., FACP

Medical Director –

St. Johns University-Physician Assistant Program

Risk factors for heat illness

ObesityFatigueDrugsAlcoholSunburnUnacclimatizedFluid deficitPrevious history of heat injuryMany medical conditionsFebrile illnessCystic fibrosisDiabetesMalnutrition

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

• Related to salt deficiency

• Victims exhibit -hyponatremia, hypochloremia, low urinary sodium and chloride levels

• Usually rapidly relieved by salt solutions

Minor Heat Illness - Heat Cramps

Minor Heat IllnessHeat 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

• 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 - two types classically described

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

Thermoregulation: Effects of EnvironmentalConditions

Causes of Hyperthermia- Disorders of excessive heat production

– Exertional hyperthermia– Heatstroke – Malignant hyperthermia of anesthesia– Neuroleptic malignant syndrome

– Thyrotoxicosis / Pheochromocytoma– Salicylate intoxication / Delirium tremens– Cocaine, amphetamines, other drugs of abuse– Status epilepticus /Generalized tetanus

Hyperthermia

Splanchnic vasoconstriction Rhabdomyolysis

Disseminated intravascularcoagulation

Thermal injury

Diminishedrenal blood flow

Renal Failure

Glomerulardamage

Myoglobinuria Hyperuricemia &urinary acidification

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

• 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

Classic Heatstroke

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

• 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 & treate- administer D50 if hypoglycemia present

Initial Treatment of Heat Stroke

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

• 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

• 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

Heat Illness Prevention

Questions ?