Dehydration and Heat Illness

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Dehydration and Heat Illness

• Sports Medicine 1

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Todays 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 NATAs Position Statement
  on Water Replacement
• Review how athletes can prevent and ATs/coaches
  can treat heat illness
• Cold Injuries?!?! In AZ????

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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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Krebs Cycle and Glycolysis
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Heat Dissipation and Heat Transfer

• Because of Law 1 of Thermodynamics, the bodys
  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

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Heat Dissipation and Heat Transfer cont.

• 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

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Heat Dissipation

• Radiation and Convection
• Dissipates most heat when temps are below 68 F
• Evaporation
• Dissipates most heat when temps are above 68 F

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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.

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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

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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.

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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

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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

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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

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Minor Heat Illness cont.

• 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.

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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 doesnt have enough
  oxygen to support their body
• Especially true at higher altitudes

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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 bodys inability to
  adequately dissipate heat
• Pure Na or water depletion forms of heat
  exhaustion are rare in athletics usually a
  combination of both.

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Heat Exhaustion/ Exertional Hyperthermia cont.

• Treatment Assess ABCs, 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

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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

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Exertional Heat Stroke cont.

• 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

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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

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Exertional Heat Stroke cont.

• Treatment
• Assess ABCs, 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

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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.

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• Conditions and their associated signs and
  symptoms

• 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

Not every patient will present with all the
signs and symptoms for the suspected condition.
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• 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

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• Exertional heat stroke
• High body-core temperature (gt40C 104F)
• 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

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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

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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 NSAIDs

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Exertional Hyponatremia

• Treatment
• Education
• Encourage salty foods
• Obtain vitals (including core temp), call 911
• Prevention
• Education, including carbohydrate drinks into
  workouts

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Conditions and their associated signs and
symptoms

• Exertional hyponatremia
• Body-core temperature, 40C (104F)
• 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

Not every patient will present with all the
signs and symptoms for the suspected condition.
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Risk factors and Populations at increased Risk

• Large or Obese Adults
• Generates more heat because of fat
• Dissipates heat less efficiently
• POORLY conditioned

• Healthy Adults
• Poor acclimatization
• Poorly conditioned
• Inexperienced in competition
• Salt or water depleted

• Elderly
• Less efficient at cooling than younger adults
  because of the aging process

• 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

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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

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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 0.20C for every 1 of body weight lost (due
  to sweating) during the activity.

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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

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Prevent Dehydration!

• 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??

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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.

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Prevention of Heat Illness

• Ensure adequate acclimatization and conditioning
  into sport
• 7-10 days of exposure into sport
• Preseason should include strength, endurance,
  skill acquisition drills in a warm environment
• Monitor atomspeheric and environmental conditions
  and enforce activity restrictions in dangerous
  situations
• Adjust workout schedule based on the
  environmental conditions
• Wear proper clothing for exercise in the heat
• No shirt? More and less risk!
• Monitor athletes for early s/s of heat illness

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Cold Injury!?!?

• Raynauds 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

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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!

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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!!