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Heat Illness/Hyperthermia Victor Politi, M.D., FACP Medical Director – St. Johns University-Physician Assistant Program.

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Presentation on theme: "Heat Illness/Hyperthermia Victor Politi, M.D., FACP Medical Director – St. Johns University-Physician Assistant Program."— Presentation transcript:

1 Heat Illness/Hyperthermia Victor Politi, M.D., FACP Medical Director – St. Johns University-Physician Assistant Program


3 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

4 Heat Illness Classification Heat Rash Heat syncope Heat cramps Heat exhaustion Heat stroke


6 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

7 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

8 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

9 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

10 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

11 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

12 Heat Exhaustion: Diagnosis Vague malaise, fatigue, headache Core temperature often normal; if elevated less than 104 0 F 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 !!


14 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

15 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 !

16 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


18 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

19 Hyperthermia Splanchnic vasoconstriction Rhabdomyolysis Disseminated intravascular coagulation Thermal injury Diminished renal blood flow Renal Failure Glomerular damage Myoglobinuria Hyperuricemia & urinary acidification

20 A catastrophic life-threatening medical emergency --- HEAT STROKE

21 Heat Stroke Diagnosis Exposure to heat stress, endogenous or exogenous Signs of severe CNS dysfunction (coma, seizures, delirium Core temperature usually 41 0 C (105.8 0 F) or more, Dry, hot skin frequent, Marked elevation of hepatic transaminases


23 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

24 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

25 Exertional Heat Stroke Like classic heat stroke- occurs during hot,humid weather Occurs sporadically - effecting young, healthy persons engaged in strenuous physical activity

26 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

27 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

28 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)

29 Treatment of early complications of Heat Stroke Shivering Convulsions Myoglobinuria Acidosis Hypokalemia Hypocalcemia


31 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

32 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

33 Fluid intake is the most critical variable Heat Illness Prevention


35 Questions ?

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