Heat illness or heat-related illness is a spectrum of disorders due to environmental heat exposure. There are two major categories: minor heat illness

[heat edema, prickly heat, heat syncope, heat cramps, and heat exhaustion] and major syndromes [heat stroke].

Heat Cramps

  • Involuntary, spasmodic contractions of skeletal muscles, usually of the calves, occasionally the thighs and shoulders.
  • Self-limited, no significant morbidity, patient’s chief complaint will be pain.
  • Due to relative deficiency of sodium, potassium, and fluid at a cellular level.
  • Treat with fluids and salt replacement PO or IV.
  • Complications: rarely rhabdomyolysis secondary to diffuse and protracted muscle spasm
  • Prevented by maintaining adequate salt intake and drinking commercial electrolyte beverages.

Heat syncope

  • Variant of postural hypotension resulting from the cumulative effect of relative volume depletion, peripheral vasodilatation, and decreased vasomotor tone.
  • Occurs in nonacclimatized individuals during the early stages of heat exposure.
  • Evaluation includes exclusion of metabolic, cardiovascular, and neurologic disorders that produce syncope.
  • Treat with rest, removal from the heat source, PO or IV rehydration.

Heat Exhaustion

  • Acute heat illness that reflects significant volume depletion and may or may not have an elevated core temperature.
  • Symptoms: weakness, malaise, lightheadedness, fatigue, dizziness, nausea, vomiting, frontal headache, and myalgias.
  • Clinical manifestations: orthostatic hypotension, sinus tachycardia, tachypnea, diaphoresis, and syncope, core temp can range from normal to 40°C.
  • Mental status remains normal.
  • Treat with volume, electrolyte replacement and rest.
  • Complications: can progress to heat stroke.

Heat Stroke

  • Core temperature higher than 40°C, CNS dysfunction, and anhidrosis.
  • High mortality rate, multiple organ system involvement.
  • CNS dysfunction can include: irritability, confusion, bizarre behavior, combativeness, hallucinations, seizures, or coma, ataxia.
  • Neurologic abnormalities can include plantar responses, decorticate and decerebrate posturing, hemiplegia, seizure.
  • Differential:
    • NMS.
    • Serotonin syndrome.
    • Infections: sepsis, meningitis, encephalitis, tetanus, typhoid.
    • Endocrine: DKA, thyroid storm.
    • Neuro: status epilepticus, hemorrhage.


Technique Advantages Disadvantages
Evaporative Simple
Readily available
Easy patient access
Difficult to maintain monitoring electrodes in position
Can be messy
Immersion Noninvasive
Logistically difficult to access
Difficult to maintain monitoring electrode and temp probes
Ice packing Noninvasive
Readily available
Poorly tolerated
Strategic ice packs Noninvasive
Readily available
Can be combined with other techniques
Poorly tolerated
Medium efficiency
Cold gastric lavage Available Invasive
Labor intensive
Water intoxication
May require airway protection
Limited human experience
Cold peritoneal lavage Theoretically beneficial Invasive
Limited human experience