Temperature-Related Emergencies

1. Temperature-Related Emergencies David A. Caro, MD

2. Temperature-Related Emergencies • Introduction Temperature Control/Physiology Mechanisms of Heat Dissipation Temperature Measurement

3. Temperature-Related Emergencies • Heat Illnesses Heat stress Heat exhaustion Heat stroke

4. Temperature-Related Emergencies • Cold Illnesses Frostbite Hypothermia

5. IntroductionHeat Control Physiology • Normal human temperature 96.8 to 100.4oF (36 -37.8oC) • Temperature can reach 104oF during strenuous exercise • Preoptic Hypothalamus – responsible for temperature control via thermoregulation

6. Temperature Emergencies • A rise in core temperature above the normal range (hyperthermia) or a decrease below the normal range (hypothermia) is the consequence of an imbalance between heat production and heat loss.

7. Heat Production Ambient Heat Temperature Heat Loss to environment

8. Skin Receptors Hypothalamus Core Receptors Thermoregulation

11. Thermoregulation Veins Hypothalamus Sweat Glands Behavior

12. Hot Cold

13. Introduction Heat Dissipation Mechanisms • Radiation - electromagnetic dissipation - 65% • Evaporation - transfer of heat to make liquid a gas - 25% • Convection - heat transferred to air and water in close proximity to skin - 8% • Conduction - direct heat transfer - 2%

14. Radiation AIR EM Radiation The body at the higher temperature emits more energy than the one at the lower temperature, and the net transfer of energy (heat) is down the temperature gradient.

15. Convection AIR MOVEMENT SKIN

16. Evaporation • . For every ml of water evaporated from the surface of the skin, 0.58 Kcal are removed from the body. • Insensible - skin, respiratory • approximately 600 ml/day • Sensible - sweat • up to 3 liters/hr

17. Temperature Measurement • Axillary - most inaccurate • TM - wide variability • Oral - affected by ventilation • Rectal • Bladder, Esophageal, PA catheter - in ICU setting

18. Heat Illnesses • Heat Stress • Heat Exhaustion • Heat Stroke

19. Heat Illness • Heat Stress Heat Cramps Heat Tetany Heat Edema Heat Syncope Prickly Heat

20. Heat Exhaustion • Syndrome of weakness, fatigue, headache, nausea, vomiting, vertigo, orthostasis, and impaired judgement • NO major CNS symptoms (seizures, coma)

21. Heat Stroke • Thermoregulatory Failure • Profound CNS dysfunction • Classic vs. exertional

22. Heat Stroke • CNS dysfunction • CV dysfunction • Hepatic dysfunction • Renal failure • Hematologic complications

23. meningitis encephalitis status seizures falciparum malaria thyroid storm medications DTs typhoid fever hypothalamic hemorrhage Heat stroke - Differential diagnosis

24. Heat stroke treatment • ABCs • Cooling • remove from heat; remove clothing • spray water/fan • ice packs/cooling blankets • lavage (NG, bladder, thoracic) • Dialysis/CP bypass

25. Heat stroke treatment • Benzos for seizures, shivering • IV fluids • replace deficits • treat rhabdomyolysis • Treat coagulopathy

26. Cold Illnesses • Hypothermia • Frostbite

27. Hypothermia • 92-95oF - Mild • 87-92oF - Moderate • < 87 oF - Severe

28. Frostbite • Spectrum - similar to burns • Mild (analagous to 1o burn) • Moderate (2o burn) • Severe (3o burn to gangrene)

29. Treatment - Mild Hypothermia • Remove wet clothing; replace with dry clothing/blankets • Ambient warming • Warmed oral fluids

30. Treatment - Moderate Hypothermia • Remove wet clothing; replace with dry • Monitor cardiac, respiratory status • Radiant/heat blanket warming • Warmed IV, oral fluids • Warmed, humidified oxygen • Warmed IV bags to groin, axillae; ? immerse

31. Treatment - Severe Hypothermia • All of the above • Careful movement; may induce V Fib • Intubate as needed • Warmed NG, Foley lavage • Warmed pleural/peritoneal lavage • Dialysis, Bypass