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Heat Illness/Hyperthermia Victor Politi, M.D., FACP Medical Director - SVCMC 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 Heat Heat Heat Heat Heat Heat Rash syncope tetany edema cramps exhaustion 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 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 Edema 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 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 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 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 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 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 Causes of HyperthermiaDisorders of diminished heat production Heatstroke (classic) Occlusive dressings Dehydration Autonomic dysfunction Anticholinergics Neuroleptic malignant syndrome Causes of HyperthermiaDisorders of Hypothalamic Function Neuroleptic malignant syndrome Cerebrovascular accidents Encephalitis Sarcoidosis and granulomatous infections Trauma Hyperthermia Splanchnic vasoconstriction Thermal injury Rhabdomyolysis Disseminated intravascular coagulation Diminished renal blood flow Glomerular damage Myoglobinuria Hyperuricemia & urinary acidification Renal Failure 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 Exertional Heat Stroke Predisposing factors include acclimatization to the heat, lack of cardiovascular conditioning, heavy clothing and dehydration 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 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 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 ?
