Exertional Heat Illness

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Exertional Heat Illness
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Response to Heat Stress

• Thermoregulation is very efficient
• 1C change in core temperature for every 25 to
  30C in ambient temperature
• For every 0.6C 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

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Thermoregulation

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

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Physiology

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

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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

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Heat Illness Spectrum
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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

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Definitions

• Heatstroke - core body temp gt 40C (104F)
• 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

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Heat Illness Spectrum
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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?

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Exertional Rhabdomyolysis

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

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Exertional Rhabdomyolysis

• Novel Exertion -gtToo much, too fast
• Rhabdo in Football two a days
• GG Ehlers et al, Journal of Athletic Training
  200237151-6
• Muscle Meltdown
• Medical Journal of Australia 1990
• 5 mile fun run, hot(88F) hilly
• Rhabdohind quarter amputation

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Exertional Rhabdomyolysis

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

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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

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Exertional Rhabdomyolysis

• Recognition
• gt 5 times the normal serum CK level
• Absolute height does not severity
• Levels Peak _at_ 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

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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 gt50,000 CK, increased creatinine ?or
  myoglobinuria present
• RTP at serum CK of 2-3,000 if asymptomatic

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Heat Illness Spectrum
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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?

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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

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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

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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?

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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 gt600m
• No timed miles
• No stadium steps to exhaustion
• Regular fluids
• Stop at first cramp

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Are there different concerns for different sports?

• Football
• Full practice gear
• New NCAA guidelines

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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