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

Thermoregulation

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

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)

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

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