Heat Illness/Hyperthermi

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Victor Politi, M.D., FACPMedical Director - SVCMC

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 tetany Heat edema 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 Hyperventilatoin not present in cool environment

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

Minimal edema - feet/ankles Not accompanied by any other significant

impairment in function Often resolves after several days of

acclimatization Brief diagnostic evaluation to rule out

thrombophlebitis, lymphedema or CHF is appropriate

Minor Heat Illness - Heat Edema

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 onan

erythematous base Rash confined to clothed areas Effected area completely anhydrotic

produnda stage- 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

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, but may be lower Dry, hot skin frequent, but sweating may

persist Marked elevation of hepatic transaminases

In 80% of cases - sudden onset Patient becomes delirious or comatose Nonspecific Prodromal symptoms lasting

minutes to hours occur in approximately 20% of cases - (reminiscent of heat stoke symptoms)

There are two types of heat stroke - classic and exertional

Both types characterized by extreme hyperthermia

and multiple metabolic, hemodynamic abnormalities

but arise in very different clinical settings

HyperthermiaA patient presents to the ED with elevated

body temperature - 1st thought ??

? Infectious etiologies/severe infectionbut 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 (exertional) Malignant hyperthermia of anesthesia Neuroleptic malignant syndrome Lethal catatonia Thyrotoxicosis / Pheochromocytoma Salicylate intoxication / Delirium tremens Cocaine, amphetamines, other drugs of

abuse Status epilepticus /Generalized tetanus

Heatstroke (classic) Occlusive dressings Dehydration Autonomic dysfunction Anticholinergics Neuroleptic malignant syndrome

Causes of Hyperthermia- Disorders of diminished heat production

Neuroleptic malignant syndrome Cerebrovascular accidents Encephalitis Sarcoidosis and granulomatous infections Trauma

Causes of Hyperthermia- Disorders of Hypothalamic Function

Hyperthermia

Splanchnic vasoconstriction Rhabdomyolysis

Disseminated intravascularcoagulation

Thermal injury

Diminishedrenal blood flow

Renal Failure

Glomerulardamage

Myoglobinuria Hyperuricemia &urinary acidification

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

Predisposing factors include acclimatization to the heat, lack of cardiovascular conditioning, heavy clothing and dehydration

Exertional Heat Stroke

Effects of Exercise in Heat

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 ?