Environmental heat diagnoses

Background

Types of heat dissipation

  • Conduction: heat exchange between two surfaces in contact (placing ice pack in axilla)
  • Convection: heat exchange between a surface and a fluid (fanning)
  • Radiation: transfer of heat between body and environment through electromagnetic waves (reliant on temperature gradient)

Heat Illness Etiology

All types are due to inadequate thermoregulation

  1. Classic Heat Illness
    • Occurs without physical exertion
  2. Exertional
    • Preceded by physical activity

Clinical Features

Heat Illness Types

  1. Heat cramps
    • Muscles cramps due to electrolyte depletion
  2. Heat syncope
    • Prolonged standing +vasodilation + volume loss → decreased central venous return → decreased CO→ decreased cerebral profusion pressure
  3. Heat exhaustion (temperature usually < 40°C)
    • headache, n/v, weakness, vertigo, no CNS dysfunction
    • Water depletion: inadequate fluid replacement to match fluid loss (sweat)
    • Salt depletion: large volume of fluid loss is replaced with water (with inadequate salt)
  4. Heat stroke (temperature usually > 40°C)
    • Similar to heat exhaustion plus CNS dysfunction (seizure, AMS), transaminitis, DIC, rhabdomyolysis

Differential Diagnosis

See also hyperthermia

Environmental heat diagnoses

Evaluation

Management

  1. Heat cramps
    • Mild: oral electrolyte solution
    • Severe: IV NSS
  2. Heat syncope
    • Supine position
  3. Heat exhaustion
    • Mild: oral fluid replacement
    • Severe: IV fluid replacement and replete electrolytes as needed
  4. Heat stroke
    • ABCs
    • Rapid cooling
    • IVF, replete electrolytes
    • Benzos: for seizures and shivering

Disposition

See Also

References

Authors:

Ross Donaldson