Hyperthermia/Hypothermia



Hyperthermia/Hypothermia


Sanjay Mehta



Introduction



  • Heatstroke carries risk of significant mortality (14%), even with adequate treatment


  • Hypothermia may require prolonged resuscitation to allow adequate rewarming


Heat-Related Illnesses

Hyperthermia vs fever



  • Fever: elevation in hypothalamic set point


  • Hyperthermia: thermoregulatory dysfunction

Thermoregulation



  • Normal body temperature is 36.0-37.5°C


Hyperthermia


Predisposing Factors



  • Age: infants and elderly


  • Reactions (malignant hyperthermia), medications (anticholinergics, diuretics, β-blockers, Ca channel blockers), and drugs (alcohol, heroin, cocaine, amphetamines)


  • Fever and infection


  • Obesity, dehydration, skin abnormalities, cystic fibrosis


  • Lack of acclimatization, fatigue, clothing


  • Previous episode of heatstroke


  • Metabolic disorders (hyperthyroidism, pheochromocytoma)


Differential Diagnosis



  • Heat exhaustion


  • Heatstroke



  • Heat syncope


  • Dehydration


  • Cardiac syncope


  • Ingestion


Minor Heat Illnesses



  • Heat edema: cutaneous vasodilatation


  • Heat cramps: severe cramps of heavily exercised muscles



    • Usually calves, arms, shoulders, and abdominals after exertion


  • Heat syncope: syncopal episode during heat exposure in unacclimatized patient


Major Heat Illnesses



  • Heat exhaustion: precursor to heatstroke Temperature regulatory mechanisms intact


  • Heatstroke: life-threatening emergency Loss of thermoregulatory mechanism


Heatstroke


Exertional Heatstroke (e.g., Unacclimatized Athlete)



  • Rapid onset


  • Severe prostration


  • Sweating intact


Classic/Nonexertional Heatstroke (e.g., Secondary to Confinement)



  • More common in infants


  • Slower onset


  • Marked dehydration


  • Sweating may be absent


Management of Heatstroke



  • Give supportive care (e.g., oxygen) and cardiorespiratory monitoring


  • Cooling measures



    • Ice packs to axillae and groin



    • Cool water spray and fan


    • Antipyretics


  • Fluid resuscitation 20 mL/kg NS or RL



    • Consider dobutamine (myocardial contractility and vasodilatation)


    • Consider internal cooling (gastric/rectal/bladder/peritoneal lavage)


  • Investigations



    • Bedside glucose


    • CBC, electrolytes, Ca, PO4, Mg, renal and liver function, coagulation studies, CPK, arterial blood gas


    • Urinalysis (i.e., myoglobin)


    • ECG


  • Admit to monitored setting



    • Stop cooling when core temperature < 38.5-39.0°C






Table 54.1 Heat Exhaustion versus Heatstroke

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Jun 22, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on Hyperthermia/Hypothermia

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