Heat Illnesses

1. Heat Illnesses

2. Scenario You are one of the doctors on duty at the Great North Run. It is an unusually hot, humid and still day (temp 18 degrees) for the time of year. A participant collapses after nearly 8 miles. He is brought to your facility which is only 20 yards away.

3. He looks and feels hot. • How do you determine if he has a heat illness? • If so why might this have occurred? • If so how will you further assess and manage him?

4. Heat illnesses • Heat exhaustion • Heat stroke

5. Factors affecting heat stress • Temperature • Humidity • Movement of air or lack of air movement • Clothing • Physical activity

8. Remember… • One case of a heat illness means: • Other cases may be heading your way • You may become affected if you’re in the same environment • You need to review what you/others are doing • Prevention better than cure: keep drinking • Sodium concentration should be 50mmol/litre • Thirst signifies dehydration • Lack of thirst does not signify hydration

9. Heat Exhaustion: Time Running Out • Most commonly encountered form of heat illness • May result from physical exertion in hot environments – cardiovascular system cannot meet combined requirements of muscular, visceral and thermoregulatory blood flow. • Increased demand for cardiac output • Reduced ECF volume • Usually both salt and water deplete • The skin is cool and clammy with sweat. • Body temperature may be normal: <39 even if collapse • No organ damage (though may be dysfunction through underperfusion)

10. Heat Exhaustion- Treatment • Check orientation – if casualty disorientated treat as heat stroke • Rest in the shade or cool place • Monitor temp and treat as heat stroke if keeps rising • Drink plenty of salt solution or electrolyte fluids • Parenteral fluids only if vomiting • Remove/loosen clothing to allow body to cool • Wetting skin aids cooling (if let water evaporate) • If unsure if heat exhaustion or heat stroke manage as if heat stroke

11. Heat Stroke – Out of time • This is an emergency!! • If you suspect someone is suffering from heat stroke act immediately • Their condition will rapidly deteriorate without treatment • Brain damage and death are possible

12. Heat Stroke • Serious medical condition that requires emergency medical attention (without prompt and effective treatment, mortality nearly 80%) • Sweating is often diminished or absent (anhidrosis more likely in classic than in exertional heat stroke), which makes the skin hot and dry • Body temperature is very high (41C and rising) • There is organ damage in heat stroke • In “right” environment: • If core temp > 40 and CNS dysfunction causing delirium or convulsion, the casualty has heat stroke • If core temp > 39 and patient unconscious, the casualty has heat stroke

13. Phases of heat stroke • Hyperthermic • Haematological and enzymatic • Renal and hepatic

14. 1. Hyperthermic phase • CNS disturbance • GI disturbance (D&V) • Hyperventilation and respiratory alkalosis

15. 2. Haematological and enzymatic phase • Leukocytosis • Clinical evidence of bleeding diathesis • Abnormal clotting • High CK and myoglobinuria

16. 3. Renal and hepatic phase • Renal impairment and failure • Hypokalaemia early, hyperkalaemia late • Casts in urine • Elevated liver enzymes

17. Organs damaged • Brain • Coagulation/haemostatic • Muscle • Liver (and therefore hypoglycaemia) • Kidneys

18. Mental confusion Delirium Chills Dizziness Loss of consciousness Convulsions or coma A body temperature of 41C or more Hot, dry skin that may be red, mottled or bluish Tachycardia Heat Stroke Signs and Symptoms

19. Differential diagnosis • Infection (esp. meningococcal sepsis, falciparum malaria) • Pontine bleed • Drug intoxication (cocaine, MDMA) • Thyroid storm

20. Heat Stroke - Treatment • ABCDE • Airway protection often needed • Go easy on the fluids: 1 – 1.5 litres enough initially – give more based on urine output (or lack of) • D stands for degrees • Cool cool cool – can start this on scene • Outcome relates to magnitude and duration of high temp • Evaporative methods usually best • Treat fits aggressively (they raise temp further) • Suppress shivering (chlorpromazine) • Avoid antipyretic

21. Parris Island Protocol For Treating Suspected Exertional Heatstroke In field, ice packed around the groin and axillary areas, and patient immediately transported to clinic on stretcher. Stretcher placed above water and ice, with carrying handles sticking out at both ends. • Sheets are dipped into icy water and used to cover and drench patient: frequently rewetted. • Copious ice added to top of sheet, and skin massaged to improve blood flow. • Head constantly irrigated with ice water and fan directed at patient. • GCS & other vital signs assessed, blood taken for laboratory analyses. • One litre of normal saline administered intravenously, as a bolus. • Potassium not administered until electrolytes determined. If temperature not lowered sufficiently, patient immersed into ice and water. Temperature usually falls to 39.5°C within 15 to 20 minutes.

22. Heat stroke • After ABC and rapid cooling intensive care may be needed for the multisystem problems that can develop • Work up needs to assess haemostasis, liver, renal function and CK • CNS dysfunction common – ALWAYS look for and treat hypoglycaemia

23. Scenario You are one of the doctors on duty at the Great North Run. It is an unusually hot, humid and still day (temp 18 degrees) for the time of year. A participant collapses after nearly 8 miles. He is brought to your facility which is only 20 yards away.

24. He looks and feels hot. • How do you determine if he has a heat illness? • If so why might this have occurred? • If so how will you further assess and manage him?