Exertional Heat Illness

1. Exertional Heat Illness

2. Response to Heat Stress • Thermoregulation is very efficient • 1*C change in core temperature for every 25* to 30*C in ambient temperature • For every 0.6*C increase in core temperature there is a 10% increase in basal metabolic rate • Hypothalamus controls thermoregulation • Ability to dissipate heat to control your core temperature

3. Thermoregulation • Four processes at work • Conduction - transfer • Convection - current • Radiation - dissipation • Evaporation - sweat

4. Physiology • Heat illness occurs when the heat generated by the body and its environment overwhelms its regulatory systems

5. Role of the GI & Immune Systems • In order to bring more blood flow to the skin to dissipate heat, the body compensates by shunting blood away from the gut • Epithelial damage causes release of endotoxins (ACSM 2003) • Exaggerated immune response • Heat shock proteins generated • Release of INF, TNF, IL1, IL6, IL2r

6. Exertional Rhabdomyolysis Heat exhaustion Heat stroke Heat cramps Heat syncope Heat Illness Spectrum

7. Definitions • Heat cramps - cramping of muscles • Profuse sweating • Etiology: sodium depletion (?controversial?) • Heat Exhaustion • Heat cramps, sweating, nausea, vomiting, headache, malaise, lightheadedness, confusion, oliguria, poor coordination • Sodium depletion or water depletion • Heat Syncope • Fainting • Inability to maintain cardiac output from peripheral blood vessel dilation

8. Definitions • Heatstroke - core body temp > 40*C (104*F) • GI and CNS effects during or after exercise • Continue to perspire • Nausea, vomiting, headache, hypotension, confusion, irritability, delirium, seizure • Complications: rhabdomyolysis, shock, DIC, cerebral edema, death

9. Exertional Rhabdomyolysis Heat exhaustion Heat stroke Heat cramps Heat syncope Heat Illness Spectrum

10. Exertional Rhabdomyolysis • Injury to skeletal muscle resulting in lysis of cell with subsequent leakage of contents into plasma • Known to be a complication of vigorous exercise • What predisposes an athlete to develop this condition?

11. Exertional Rhabdomyolysis • Predisposing factors • Overweight or unfit • Fever, diarrhea viremia, or heat stress • Drugs • Novel overexertion • Inherited muscle enzymopathy • Sickle Cell Trait??

12. Exertional Rhabdomyolysis • Novel Exertion ->Too much, too fast • Rhabdo in Football two a days • GG Ehlers et al, Journal of Athletic Training 2002;37:151-6 • Muscle Meltdown • Medical Journal of Australia 1990 • 5 mile fun run, hot(88F) & hilly • Rhabdo:hind quarter amputation

13. Exertional Rhabdomyolysis • Muscle enzymopathy • Inherited disorders implicated in recurrent exertional rhabdomyolysis or ongoing rhabdomyolysis • McArdles or Myotonic dystropy • Treem 1987, Argov and Dimauro 1983

14. Exertional Rhabdomyolysis • Sickle Cell Trait • 1 in 12 African Americans • Generally benign with no anemia • Cramping & hyperventilation due to lactic acidosis • Sickling collapse in all-out exertion • Over 80 cases; 10 deaths in college football • Unlike heatstroke: • Collapse early in 1st few minutes running • Athlete can talk after they hit the ground

15. Exertional Rhabdomyolysis • Recognition • > 5 times the normal serum CK level • Absolute height does not = severity • Levels Peak @ 24-36 hours • Failure to decline indicates and ongoing process • Myoglobinuria increases risk of ARF • Urine dip: positive for blood • Urine micro: no red cells seen

16. Exertional Rhabdomyolysis • Treatment • Maintain vital signs • Get to ER fast • IV fluids to maintain urine flow • Can give 50% of sodium as bicarb • Corrects acidosis, controls hyperkalemia, makes myoglobin more soluble • Consider mannitol and furosemide • Dialyze as necessary for ARF • Hospital at >50,000 CK, increased creatinine ?or myoglobinuria present • RTP at serum CK of 2-3,000 if asymptomatic

17. Exertional Rhabdomyolysis Heat exhaustion Heat stroke Heat cramps Heat syncope Heat Illness Spectrum

18. Prevention in Athletic Competition • What factors increase the risk? • Is water enough? • What is safe for competition? • Are there different consideration for different athletes? • Are there different concerns for different sports?

19. Risk Factors for Heat Illness • Drugs: alcohol, ephedra • Poor nutrition: eating disorders • Poor hydration or dehydration • Chronic diseases: Diabetes, HTN, sweat gland dysfunction • Acute illness: URI, gastroenteritis, sunburn

20. Dehydration Debate • Is water enough to overcome risk factors? • Noakes: argues that people still develop this condition even why they exercise in a fully hydrated state • ACSM: 150-300 ml of water or sports drink every 15 minutes • Avoid preoccupation with H2O intake

21. What is safe for competition? • More emphasis on acclimatization • Work-rest cycles during different heat loads • Monitor daily weights in an athlete • When should an event or practice be cancelled?

22. Are there different considerations for different athletes? • Sickle cell trait • Should we be screening for the condition? • Precautions • No one day fitness test • No sprinting >600m • No timed miles • No stadium steps to exhaustion • Regular fluids • Stop at first cramp

23. Are there different concerns for different sports? • Football • Full practice gear • New NCAA guidelines

24. Final Points • Maintain a high index of suspicion in an athlete playing under extreme conditions • Appropriate monitoring of athletes by medical personnel is important in preventing heat illness • Daily weights • Consider risk of sickle cell trait • Water is not the only answer • Slower is better than dead • Graded training programs • Work- Rest cycles