heat illness

Bouchama's definition: temp>40C, hot+dry skin and neurological s/s (coma, delirium, seizures)

Exertional: syndrome associated with a raised core temperature and disordered thermoregulation which occurs on a spectrum of severity, ranging from mild to life threatening during or immediately after physical activity
Etiology 'Classic' heatstroke = non-exertional.

Heat exhaustion - systemic disorder; sweating++
Heat stroke - associated with SIRS → multiorgan problems including encephalopathy
Epidemiology Risk factors:
- medications - cholinergic; SSRIs, etc.
- extremes of age
Clinical presentation C: hypovolaemic shock, dry skin
D: focal neurology
E: Rhabdomyolysis, ATN, low phosphate, high CK
Pathogenesis Direct cell damage likely due to protein denaturation → ↑ vascular permeability
Activation of pro-inflammatory pathways
Dehydration → renal failure
Translocation of gut flora → inflammatory response
Diagnostic investigations FBC, U+E, LFT, CK... looking for end organ damage and other exertional badness eg hyponatraemia
Management FPHC: "S3F" - shade, strip, spray, fan
Cool before transporting/before core temp
Cold water immersion most effective for EHI - target core temp 38.5C
- risk of rebound hyperthermia
- contraindicated with arrhythmia, cardiogenic shock
- should be done with core temp monitoring
"Immediately active cool using whole body (from neck down) water immersion technique (1-26 °C) until core temperature < 39°C. Where water immersion is not available, use any technique that provides the most rapid rate of cooling." - Resus Council

Fluid resuscitation
- no evidence for cool IV fluids prehospital