Exertional Heat Illness

1. Exertional Heat Illness Sports Injury Management

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 • New NCHSAA Conditioning Guidelines

24. HOT WEATHER GUIDELINES & FOOTBALL CONDITIONING NCHSAA 2011 DAY 1 & 2: Helmet, shorts, and football shoes; 3 hour limit Optional: 1 hour walk-through, 3 hours must separate DAY 3 – 5: Helmet and shoulder pads; 3 hour limit Optional: 1 hour walk-through, 3 hours must separate DAY 6 – 8: Full gear and contact Optional: Double Practice 3 hours max per practice, max of 5 combined; must be separated by 3 “cool” hours OR Single Practice 3 hours maximum, 1 hour walk-through; 3 “cool” hours must separate NOTE - Double practice days must be followed by a single practice day (with 1 hour walk-through option) Double practice day followed by an OFF DAY allows for following day to be a double practice day All double practice days limited to 3 hours per practice, but no more than 5 total hours of both practices 3 “cool hours” must separate a double practice and 1 hour walk-through

25. HOT WEATHER GUIDELINES & FOOTBALL CONDITIONING NCHSAA 2011 Continued….. Day 9: Full gear and contact 1st available scrimmage 7 hours of pre-season scrimmage time is allowed Day 9 -14: Follow double practice / single practice rotation options NOTE: Beginning with day 6 - 14, or up to the beginning of the 180 day school year – whichever occurs first – the double practice/single practice option must be followed REMINDERS: - Walk-through’s can be no more than 1 hour in length; no equipment can be used (helmets, shoulder pads, etc. ) - Double practice days must be followed by a single practice day (with 1 hr walk- through) - Double practice days followed by an OFF DAY allows for the following practice day to be a double practice day - Double practices and 1 hour walk-through’s must be separated by 3 “cool” hours - Warm-up, stretching, cool-down, walk-through, conditioning, and weight room activities are part of practice limits.

26. 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

27. Thanks to…. • Spencer Elliott, MA, LAT, ATC Carolinas Medical Center Concord, NC (There’s no reason to re-invent the wheel!)