Heat Stress

With Sydney temperatures consistently reaching the high 30’s and early 40’s recently it is perhaps timely to revise heat related illness. It is also worth considering the steps we can take to keep ourselves cool in the same environmental conditions.

Heat related illness covers a spectrum which, at the most extreme end, includes heat stroke. This is defined as hyperthermia >40 degrees, associated with neurological dysfunction. The neurological dysfunction can manifest in many ways including ataxia, delirium, seizures and coma. The patient may also be tachycardic and hypotensive (echo may show either a hypodynamic or hyperdynamic LV). Sweating may be absent. Unrecognised heat stroke carries a mortality of up to 30%.


Aggressive cooling in the field can prevent a cascade of organ dysfunction and significantly improve prognosis. Initial management and cooling methods will be dictated by resources and environment but consider:

  • Moving the patient into the shade
  • Using pack equipment to create some shade e.g. the warming blanket could be used as a canopy if bystanders are able to hold it aloft.
  • Remove the patients clothing
  • Place wet towels or sheets over the patient (road crew may have some)
  • Place ice packs in axillae, groin, neck
  • Try to create some airflow over the patient if possible (not always practicable in the prehospital environment)
  • Stop cooling at approximately 38-38.5 degrees core temp to avoid overshoot hypothermia.
  • Paracetomol is ineffective

Don’t forget standard resuscitation measures:

A = RSI if patient is obtunded and unable to protect airway

B = Ventilate as required. Be aware that pulmonary oedema and ARDS may accompany heat stroke if you are having difficulty ventilating

C = iv fluids may be needed but don’t equate hyperthermia with hypovolaemia. Depending on clinical circumstances, the patient may be either mildly or profoundly volume depleted. Be aware of dilutional hyponatraemia in endurance athletes consuming lots of sports drinks. This can be an important differential for altered LOC and seizures.

Inotropes may be required if shock is refractory to fluid resuscitation but be aware that adrenaline and noradrenaline will cause vasoconstriction that may impair cooling.

D = Benzodiazepines for seizures, don’t forget to check a BSL

Self Care

Self-care is important on these missions as crew members are being exposed to the same environmental conditions as the patient and may have had to exert themselves to get there (winch, bush walk etc.) Make sure you are well hydrated pre mission and carry additional water. Urine colour is the best guide to your hydration status. Ice packs are available in the ready room and can be used by crew if needed. Consider your uniform sunhat if your head is exposed. Sun cream is also available in the ready room. If you are feeling unwell due to heat, communicate this immediately to your crew.

Heat stress

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