Exertional Heat Illness

Sports Injury Management

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

Thermoregulation

• Four processes at work– Conduction - transfer

– Convection - current

– Radiation - dissipation

– Evaporation - sweat

Physiology

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

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

Heat Illness Spectrum

Heat cramps Heatsyncope

Heat exhaustion

Heat stroke

Exertional Rhabdomyolysis

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

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

Heat Illness Spectrum

Heat cramps Heatsyncope

Heat exhaustion

Heat stroke

Exertional Rhabdomyolysis

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?

Exertional Rhabdomyolysis

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

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

Exertional Rhabdomyolysis

• Muscle enzymopathy– Inherited disorders implicated in recurrent

exertional rhabdomyolysis or ongoing rhabdomyolysis

• McArdles or Myotonic dystropy

• Treem 1987, Argov and Dimauro 1983

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

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

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

Heat Illness Spectrum

Heat cramps Heatsyncope

Heat exhaustion

Heat stroke

Exertional Rhabdomyolysis

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?

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

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

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?

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

Are there different concerns for different sports?

• Football– Full practice gear– New NCAA guidelines– New NCHSAA Conditioning Guidelines

HOT WEATHER GUIDELINES & FOOTBALL CONDITIONINGNCHSAA 2011

DAY 1 & 2: Helmet, shorts, and football shoes; 3 hour limitOptional: 1 hour walk-through, 3 hours must separate

DAY 3 – 5: Helmet and shoulder pads; 3 hour limitOptional: 1 hour walk-through, 3 hours must separate

DAY 6 – 8: Full gear and contactOptional: 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 practices3 “cool hours” must separate a double practice and 1 hour walk-through

HOT WEATHER GUIDELINES & FOOTBALL CONDITIONINGNCHSAA 2011

Continued…..

Day 9: Full gear and contact

1st available scrimmage7 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.

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

Thanks to….

• Spencer Elliott, MA, LAT, ATC

Carolinas Medical Center

Concord, NC

(There’s no reason to re-invent the wheel!)