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Dehydration and Heat Illness
Dehydration and Heat Illness
Sports MedicineMr. Smith
Sports MedicineMr. Smith
Today’s Objectives• Learn about how the body produces heat• Understand how heat is dissipated and transferred from the
body• Discuss the minor, moderate, and severe heat related
illnesses• Discuss how hyponatremia is involved with heat illness• Learn the risk factors associated with a heat illness• Review Dehydration and NATA’s Position Statement on
Water Replacement• Review how athlete’s can prevent and AT’s/coaches can
treat heat illness• Cold Injuries?!?! In AZ????
Heat Production• Thermodynamics-
– Law #1 states: “energy can neither be created nor destroyed”
– Heat production occurs as a result of muscle work• Muscles that produce heat are working 15-20 times
their resting rate– However, the human body only uses 15-30% as energy, the
other 70 to 85% is converted to heat and must be dissipated or the core body temperature will rise
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Heat Dissipation and Heat Transfer
• Because of Law #1 of Thermodynamics, the body’s core temperature is transient– Without our “internal thermostat”, heat
generated at rest would increase body temperature 1° C every 5 minutes!!
– Early in exercise• Heat production is greater than heat loss; even
more so in a hot environment….– Causes our core internal temp to rise quickly
• A rise in core temp is sensed and is regulated by thermodetectors, a.k.a- internal thermostat– Sends a message to our brain to initiate
sweating and increase peripheral blood flow
• Heat loss:– Nonevaporative vs. Evaporative
• Conduction• Convection• Radiation
Heat Dissipation and Heat Transfer cont.
Heat Dissipation and Heat Transfer cont.
Heat Dissipation
• Radiation and Convection– Dissipates most heat when temps are below 68° F
• Evaporation– Dissipates most heat when temps are above 68° F
Conductive• Is when a warmer body comes into contact with a cooler
body– The warmer body will result in transfer of heat to the cooler
body
– Example: • After track practice you are so hot that you lay on the cool floor in the E
building to cool down. In this process, you warm up the floor and you temporarily cool the part of your body that was exposed to the floor. Conduction is you warming the floor.
Convection
• Is a result of forced fluid flow (usually cooler) across a warmer relatively stationary surface– Superficial blood flow transfers heat by this method
• When dilated peripheral blood vessels come in contact with circulating air that has a direct contact with skin surface
– Also related to:• The amount of exposed skin• The speed of air circulation• Skin thickness! The thicker the skin the harder to cool the
body!
– Example: • Cool/warm wind blowing outside on a hot temperature body
Radiation• When energy (heat) flows from high temperature
to low temperature, results in heat transfer through electromagnetic waves
– Example:• Exposed human skin is a radiator. The more total area of
exposed skin, the more energy (heat) is radiated to the environment, assuming of course that the body is warmer than its surroundings.
– To minimize the amount of radiative heat lost to the environment make sure all exposed skin are covered. This includes the head, face, neck, and hands.
Evaporative Heat Dissipation• Occurs when a liquid turns into a gas
– Sweating usually begins when the body temperature is above 98.6° F
• Cooling as a result of sweating is related to:– Skin surface area– Velocity of air crossing the skin surface area– The sweat rate of the athlete
Problems with Heat Dissipation• Hot/Humid Climates
– Evaporative cooling is indirectly related to humidity– In dry and hot conditions, evaporation can account for 98% of heat
loss– In temps above 95° F, convection and radiation do not contribute
to heat loss, but sun radiation can cause heat gain
– In normal, heat acclimatized athletes:• Core temps during exercise can range from 98-104° F with normal
performance
– If these systems fail….• Core temps will continue to rise leading to dangerous levels of heat
stress on the body– To prevent the damage: reduce exercise, drink water and salt
replacement, improve nonevaporative heat loss
Minor Heat Illness
• Heat Edema– S/S: edema of hands and feet,
heat rash– Predisposition: unacclimatized
persons who exercise in hot environments
– Treatment: rest and/or elevation of the affected extremity. Generally resolves after acclimatization to heat
– Complications: Usually none
• Heat Cramps– S/S: Severe, spreading muscular tightening and spasm seen during or
after intense, prolonged exercise in the heat. Usually affects lower limb, larger muscles- but any muscle can be affected
– Etiology- Fluid loss, muscle fatigue, salt loss– Predisposing factors: Lack of acclimatization, salty sweaters, sickle cell
anemia– Treatment: Rest, cooling down, ice, massage, fluid and salt
replacement. If not improving within 30-45 mins call EMS because IV fluids may be needed.
– Prevention: Conditioning and heat acclimatization. Salty sweaters may need more salt consumption in their diet in hotter climates.
– Complications: Can lead to heat exhaustion if not treated. Rhabdomyolisis should be suspected if severe and prolonged episodes occur.
Minor Heat Illness cont.Minor Heat Illness cont.
Sickle Cell Anemia• Present in 5-8% of the
African American population• Normal and abnormal
shaped hemoglobin are produced. The abnormal
shaped hemoglobin carries less oxygen.
• With exercise the person doesn’t have enough oxygen to support their body– Especially true at higher
altitudes
Heat Exhaustion/ Exertional Hyperthermia
• Most common form of heat illness• S/S: Elevated (rectal) temperature (above 104° F),
decreased BP, increased pulse, profuse sweating, mild mental status change (mild confusion, mild agitation/ irritability, mild emotionality, mild uncoordination), fatigue, headache, nausea, vomiting, heat cramps, chills/goosebumps
• Etiology: Exertional heat stress and dehydration, which results in the body’s inability to adequately dissipate heat– Pure Na+ or water depletion forms of heat exhaustion are rare
in athletics… usually a combination of both.
Heat Exhaustion/ Exertional Hyperthermia cont.
• Treatment: Assess ABC’s, obtain/ monitor vitals, rest in cool, shaded environment with air circulation- if more severe S/S are present- ice bath, shock position, oral rehydration with an electrolyte containing solution. If vomiting, diarrhea or decreased mental functioning- 911 for IV fluid. S/S usually resolve within a few hours
• Complications: Usually one significant heat illness is predictive of future episodes of heat illness
Exertional Heat Stroke
• A very serious medical emergency!!• Extreme hyperthermia (rectal temperature above 104° F),
with thermoregulatory failure and profound central nervous system dysfunction!
• S/S: Elevated rectal temperature, significantly lowered BP, elevated pulse, pronounced mental status change (irritability, ataxia, confusion, disorientation, syncope, hysterical or psychotic behavior, seizure and or coma), Cessation of sweating, epistaxis, bruising, peripheral edema, fatigue, dizziness, nausea, vomiting, heat cramps, and chills
• Etiology: Biggest threat is when wet bulb globe temperature is above 82° F during higher intensity exercise (more than 72% of VO2 max) and the duration of exercise is greater than 1 hour
• If wet bulb globe temperature is unavailable:
Exertional Heat Stroke cont.
Exertional Heat Stroke cont.
• Pathophysiology: How heat stress causes damage to the body– Damage to cells via denaturation of proteins thereby interrupting
cellular function– Release of inflammatory proteins, which contribute to circulatory
collapse and systemic damage– Damage to the vascular endothelium
• Predisposing Factors– Genetics (?), dehydration, lack of acclimatization, negative
sodium imbalance, finish line illness (near finish line, dehydration, increasing speed (increased muscle heat and increased blood flow), and rise in core temp
Exertional Heat Stroke cont.
• Treatment:– Assess ABC’s, remove from hot environment to a cool, shaded
area with airflow, remove necessary clothing, obtain vitals and continue to monitor.
– Methods of measuring temperature other than true core temperature (RECTAL) should not guide diagnosis and therapy!!
• Oral, tympanic membrane, and axillary temperatures do not correlate well with core temperatures in heat injured patients.
– “Cold water immersion provides the fastest whole body cooling rate and the lowest morbidity and mortality for exertional heat stroke”
• Can also provide cold water towels directly on athlete in combination with large fan to speed evaporation
Exertional Heat Stroke cont.• Complications:
– CNS-confusion, coma, seizures, cerebral or spinal infarction
– Cardiovascular- arrhythmias, myocardial infarction, pulmonary edema, shock
– GI- Diarrhea and vomiting, upper GI bleeds, liver damage
– Hematologic- fibrinolysis, thrombocytopenia
– Musculoskeletal- rhabdomyoloysis, myoglobinemia
– Pulmonary- hyperventilation, adult respiratory distress syndrome, pulmonary infarction
– Renal- Acute renal failure
• Return to Play– Athletes often experience a lack of heat tolerance and possess residual
thermoregulatory compromise that may last up to several months.
Exercise-associated muscle (heat) cramps
• Dehydration• Thirst• Sweating• Transient muscle cramps• Fatigue
Heat syncope• Dehydration• Fatigue• Tunnel vision• Pale or sweaty skin• Decreased pulse rate• Dizziness• Lightheadedness• Fainting
Conditions and their associated signs and symptoms*
*Not every patient will present with all the signs and symptoms for the suspected condition.
Exercise (heat) exhaustion• Normal or elevated body-core
temperature• Dehydration• Dizziness• Lightheadedness• Syncope• Headache• Nausea• Anorexia• Diarrhea
• Decreased urine output• Persistent muscle cramps• Pallor• Profuse sweating• Chills• Cool, clammy skin• Intestinal cramps• Urge to defecate• Weakness• Hyperventilation
Exertional heat stroke• High body-core temperature
(>40°C [104°F])• Central nervous system
changes• Dizziness• Drowsiness• Irrational behavior• Confusion• Irritability• Emotional instability• Hysteria• Apathy• Aggressiveness• Delirium
• Disorientation• Staggering• Seizures• Loss of consciousness• Coma• Dehydration• Weakness• Hot and wet or dry skin• Tachycardia (100 to 120
beats per minute)• Hypotension• Hyperventilation• Vomiting• Diarrhea
Exertional Hyponatremia
• Usually seen in endurance athletes– 5-13% of marathon participants, .3-27% ultra-
endurance participants• Presenting Symptoms:
– Not feeling right, nausea, lightheadedness, malaise, lethargy, cramps, vomiting
• Signs of fluid overload:– Edema, weight gain, emesis. Tachycardia and mental
status change (confusion, seizure, coma, and death)• Etiology:
– Excessive fluid intake (water), loss of salt through sweating
Exertional Hyponatremia
• Predisposing factors:– Endurance activity lasting longer than 4 hours
• Especially in hot and humid temp
– BMI less than 20– Weight gain during endurance event
• Runners who gain 0.75 kg of body weight at 7x more likely to develop hyponatremia
– Women, especially those who are in the late stage of menstrual cycle
– Inexperienced athletes in endurance events– Use of NSAID’s
Exertional Hyponatremia
• Treatment:– Education– Encourage salty foods– Obtain vitals (including core temp), call 911
• Prevention:– Education, including carbohydrate drinks into
workouts
Exertional hyponatremia• Body-core temperature, 40°C
(104°F)• Nausea• Vomiting• Extremity (hands and feet)
swelling• Low blood-sodium level• Progressive headache• Confusion
• Significant mental compromise • Lethargy• Altered consciousness• Apathy• Pulmonary edema• Cerebral edema• Seizures• Coma
Conditions and their associated signs and symptoms*
*Not every patient will present with all the signs and symptoms for the suspected condition.
Risk factors and Populations at increased Risk
• Healthy Adults:– Poor acclimatization
– Poorly conditioned
– Inexperienced in competition
– Salt or water depleted
• Large or Obese Adults– Generates more heat because
of fat
– Dissipates heat less efficiently
– POORLY conditioned
• Children– Produce more metabolic heat per
mass unit than adults– Children absorb more heat from
environment– Children sweat less, require
greater core temps increases to trigger sweating
• Elderly – Less efficient at cooling than
younger adults because of the aging process
Risk factors and Populations at increased Risk
• History of previous heat injury– CNS “thermostat” has been
injured, therefore a higher “set point” activates sweating
• Women of reproductive age right after their menstrual cycle– Smaller plasma volume
• Acute and Chronic Illness• Sickle Cell Anemia• Fever!
• Alcohol, drugs, and medication abuse
Dehydration
• Those supervising athletes should be able to recognize the basic signs and symptoms of dehydration: thirst, irritability, and general discomfort, followed by headache, weakness, dizziness, cramps, chills, vomiting, nausea, head or neck heat sensations, and decreased performance.
• A major consequence of dehydration is an increase in core temperature during physical activity, with core temperature rising an additional 0.15 to 0.20°C for every 1% of body weight lost (due to sweating) during the activity.
Prevent Dehydration!
• Thirst is not an adequate indicator of how much fluids we should be consuming– Athletes may not become thirsty until they have
become more than 5% dehydrated• Athletes should know how to calculate sweat
loss under similar conditions– Weight before activity– Perform at competition level x 1hour– Track fluid intake– Record weight after activity– To determine hourly sweat rate: add the difference in
body weight in oz to the volume of fluid consumed
• To determine how much water to drink every 15 minutes: divide the hourly sweat rate by 4. This is now YOUR guideline for how much water to consume every 15 minutes during activity
• To change how much consumption is needed according to environmental factors (hotter or cooler days): repeat the measurements and note the temperature change.
• Too much work??
Prevent Dehydration!
NATA Position Statement on Fluid Replacement
• “To ensure proper pre-exercise hydration, the athlete should consume approximately 17 to 20 fl oz of water or a sports drink 2 to 3 hours before exercise and 7 to 10 fl oz of water or a sports drink 10 to 20 minutes before exercise.”
• “Proper hydration during practice generally requires 7 to 10 fl oz every 10 to 20 minutes of practice. Athletes benefit from including carbohydrates (CHOs) in their rehydration protocols. Consuming CHOs during the pre-exercise hydration session (2 to 3 hours pre-exercise), along with a normal daily diet increases glycogen stores. If exercise is intense, then consuming CHOs about 30 minutes pre-exercise may also be beneficial. Include CHOs in the rehydration beverage during exercise if the session lasts longer than 45 to 50 minutes or is intense.”
• “Fruit juices, CHO gels, sodas, and some sports drinks have CHO concentrations greater than 8% and are not recommended during an exercise session as the sole beverage. Athletes should consume CHOs at least 30 minutes before the normal onset of fatigue and earlier if the environmental conditions are unusually extreme, although this may not apply for very intense short-term exercise, which may require earlier intake of CHOs.”
Prevention of Heat Illness
Know the medical history of the athletesGauge heat and humidity of playing surface before practiceAcclimitization period is 7-10 daysProvide time for rest, electrolyte and water replacementMonitor body weight before and after practice
If they lose 3-5% of BW must gain back 80% of thatWear moisture wicking and light colored clothing (Drifit)Never wear rubber suitsHave athletes change shirts if saturated with sweatProvide rest periods in cool areasMake sure they drink water often
Cold Injury!?!?
• Raynaud’s Phenomenon– Presentation:
• Intital “white” ischemic phase may be followed by a “blue” cyanotic phase, before the “red” hyperemic phase begins
– Treatment:• Warming the affected extremity
– Prevention:• Avoid direct cold exposure
Cold Induced Urticaria
• Affects those most commonly in the warm up in cold weather
• Presentation:– Wheals, hives, angioedema, anaphylaxis involvement
• Prevention– Achieved with proper clothing and avoidance of cold
ice water
• Treatment:– Antihistamines, if anaphylaxis is present and epi pen
may need to be given. Call 911!
If known that this condition exists and the athlete, parent, and physician gives the ATC permission for use of an epi pen, the injection must be given HARD into the vastus lateralis of the quad!!
