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Heat Related Illness Main

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Other Names

  • Heat Related Illness
  • Exertional Heat Illness

Background

  • This page refers to the spectrum of heat-related illnesses due to exercise or environmentally induced hyperthermia

History

Epidemiology

  • Incidence
    • Among US high school athletes, 1.6 cases per 100,000 exposures[1]
    • Incidence among US Armed Forces in 2017 was 1.41 per 1,000 person years[2]
    • Increase in Emergency Department visits from 2006 to 2010 to 5 per 10,000 visits[3]
  • Prevalence
    • Among US high school athletes, 9000 cases annually[1]
    • In the US Armed Forces in 2017, there were 2,163 cases of heat related illness, 464 cases of heat stroke[2]
  • Mortality
    • #3 cause of death in high school athletes[4]
    • In one study of ED patients, 12% were admitted and the mortality rate was 0.07%[3]
    • According to the National Oceanic and Atmospheric Administration, it is the #1 cause of weather related fatalities annually (need citation)
    • According to the CDC, 8081 deaths were reported between 1999 and 2010, with the majority occurring between May and September[5]
  • Sport
    • The highest incidence is in American Football at 4.5 cases per 100,000 athlete exposures
    • 31 players died from exertional heat stroke between 1995 and 2008[6]

Pathophysiology

  • General
    • Heat-related illnesses should be thought of as a continuum
    • On one end is heat cramps and at the other is heat stroke
    • Early recognition and prompt treatment are keys to the prevention of morbidity and mortality
  • Heat Wave
    • Rising global temperatures are likely to increase incidence of heat wave[7]
    • Urbanization with development of inner-city heat islands likely contribute
    • According to the U.S. National Weather Service, heat waves kill more people, on average, than any other extreme weather event[8]

Terminology

  • General
    • Heat Related Illness: general term to describe any illness related to heat exposure or exertional hyperthermia
    • Exertional Heat Illness (EHI): general term to describe any illness related to heat exposure or exertional hyperthermia
  • Minor Pathology
    • Milaria Rubra: Acute inflammation of sweat ducts caused by blockage of pores
    • Heat Edema: Self-limited, mild edema of feet, ankles, and hands
    • Sunburn: reddening, inflammation, blistering and peeling of the skin
    • Heat Tetany: Respiratory alkalosis, extremity/circumoral paresthesias, carpopedal spasm
    • Heat Cramps: Painful, involuntary, spasmodic contractions of skeletal muscles
  • Major Pathology
  • Other
    • Wet Bulb Globe Temperature: measure of the heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, sun angle and cloud cover
    • Heat Acclimatization: Adaptive physiological and perceived exertion change that occurs with repeated exposure to exercise heat stress
    • Heat Tolerance Testing: Standardized testing to assesss patients tolerance of heat following an EHI
    • Heat Illness Symptom Index (HISI): Proposed to identify mild forms of heat illness based on subjective symptoms
      • Show's promise in an early study in Division 1 football athletes, requires more research[9]

Thermoregulation

  • Normal
    • Heat stress produces a predictable cascade of cellular events events.
    • Peripheral vasodilation: produce heat loss, shunt blood from the central circulation
    • Sweating and vaporization of the sweat releases heat
    • Sodium loss in sweat can be significant, can play a role in dehydration
    • Cardiopulmonary responses: tachycardia, increased cardiac output, and increased minute ventilation
    • Responses can be impaired by dehydration and excess salt loss
  • Acclimatization
    • Acclimatization to a hotter environment may take several weeks
    • Improved sodium retention, increased renal glomerular filtration rate, enhanced cardiovascular performance occur
    • Help to prevent organ damage
    • Heat shock proteins: serve to assist the cell in tolerating the heat, present in most cell lines
  • Heat exchange
    • Heat exchange occurs via conduction, convection, radiation, and evaporation
    • All methods are dependent on the presence of a heat gradient
    • Heat transfers from a hotter object to a cooler one
    • Loss of this heat gradient by certain environmental conditions can inhibit appropriate thermoregulation
    • Conduction: direct transfer of heat during contact with a cooler object
    • Convection: cooling of the air around the body by way of cooler air passing over the warmer exposed skin
      • Method depends on wind current to bring cooler air to the body (eg, fan)
      • Alternatively, movement of the body through the environment (eg, cycling)
    • Radiation: direct release of heat from a body into the environment[10]
      • Works well if the body temperature exceeds the ambient temperature
      • High ambient temperature reduces heat gradient, does not allow for heat loss from the body to the environment
    • Evaporation: occurs via perspiration[11]
      • Most effective way to release heat
      • Up to 600 kcal/h of heat can be dissipated by this method

Risk Factors

  • Demographic
    • Infants (particularly when confined in closed car)[12]
    • Prepubescent children[13]
      • Attributed to: high ratio of surface:mass, immature thermoregulatory system, small blood volume, low sweating rate
    • Elderly
    • Obesity
    • Race: Asian/ Pacific Islander
    • Gender: Male > Female
  • Functional
    • Poor physical fitness
    • Low work efficiency
    • Reduced skin area to mass ratio (eg, large muscle mass, obesity)
  • Environmental
    • Warm or hot weather
    • Unusually hot for region or season
    • Heat wave (defined as >3 d of >32°C (90°F))
    • Increased humidity
  • Medication
    • Diuretics
    • Anticholinergics
    • Beta blockers
    • Antihistamines
    • Antidepressants includig Tricyclic antidepressants
    • Stimulants (amphetamines, cocaine, ecstasy, ephedra)
    • Antiepileptic Drugs
    • ACE inhibitors/ ARBs
    • Decongestants
    • Lithium
  • Drugs
    • Alcohol use
    • Drug use, especially stimulants and amphetamine like drugs
  • Sports
    • American Football
  • Occupations
    • Firefighter
    • Agricultural workers
    • Landscapers
    • Soldiers and Military Personnel
  • Behavioral
    • Overmotivation or pressure from peers and coaches to perform beyond their physiological capability
    • Leadership or organizational structure
  • Training Related
    • Wearing heavy clothes, equipment, or uniforms
    • Inappropriate work to rest ratios
    • Inadequate heat acclimatization for current conditions
    • Heat stress in the previous 1-3 days
    • Poor or under hydration
    • Lack of access to shade, air conditioning
  • Health Conditions
    • Viral or bacterial infections
    • Fever
    • Diarrhea or vomiting
    • Skin disorders (rash, large area of burned skin)
    • Diabetes Mellitus
    • Cystic fibrosis/trait
    • Cardiovascular disease
    • Sunburn (impaired sweating mechanisms can place a patient at risk)
    • Sweat gland dysfunction
    • Xray radiation
  • Congenital
    • Ectodermal Dysplasia
    • Chronic Idiopathic Anhidrosis
    • Malignant Hyperthermia
    • Sickle Cell Trait
  • Unknown
    • Previous heat stroke has been suggested as a risk factor, not currently supported by evidence
  • Not associated/ risk factor

Differential Diagnosis

Prevention

WBGT levels for modification or cancellation of workouts or athletic competition[14]
  • General
    • Prevention is more effective, easier than treatment
    • Knowledge of signs and symptoms of heat illness for all stakeholders (athletes, parents, coaches, medical staff)
    • Individuals with early signs of illness should not be allowed to participate in physical activity
    • Avoid stimulants (ephedra, etc)
  • During warm weather/ heat wave[15]
    • Stay in air-conditioned homes or other air-conditioned premises (e.g., shopping malls or movie theaters)
    • Use fans
    • Take frequent cool showers
    • Decrease exertion
    • Increase social contact to counteract isolation
  • Training/ Work
    • Acclimatize to changed environmental conditions
    • Match the level of physical exertion to the degree of physical fitness
    • Avoid hot times of the day for training schedules
    • Remove vapor-barrier equipment and clothing that interfere with sweat evaporation
    • Maintain a proper hydration regimen
    • Schedule rest periods during activity
Acclimatization Guidelines for Football[16]
  • Heat acclimatization
    • Definition: Adaptive physiological and perceived exertion change that occurs with repeated exposure to exercise heat stress
    • Improve physical function in heat, reduce physiological strain[17]
    • Recommend 1-2 weeks to induce most physiological adaptations with optimize performance, reduce risk of EHI[18]
    • Accomplished by gradually increasing intensity, duration of exercise during daily heat exposure
Fluid Management During Exertion: Specific Guidelines[16]
  • Hydration
    • Dehydration directly contributes to heat exhaustion[19]
    • Direct link to EHI and EHS have not been established
    • Rehydration strategies are important for athletes to safely perform in warm or hot conditions
    • Best done by combing eating with fluid intake
    • If symptoms of dehydration (dizzy, tachycardic, fatigue, headache), use oral rehydration fluids with electrolytes
    • Recommend 16 oz 1 hour before exertion, then 4-8 oz per 15-20 minutes of exertion
    • Monitor body weight changes, thirst, urine volume or concentration[20]
  • Clothing
    • Uniform wear can decrease the amount of skin surface available for evaporation[21]
    • Clothing should be light colored and oose fitting
    • It should be made from lightweight, open-weave mateial
    • Wearing fewer items of clothing seems to correlate with temperature tolerance
  • Administrative strategies
    • Site leaders should change training sessions by adding longer and more frequent rest breaks
    • This allows heat dissipation and shorter bouts of high intensity exercise duration to decrease heat production
    • Longer rest breaks permit better fluid replacement
    • Factors
      • Heat acclimatization status of participants
      • Fitness and age of participants
      • Intensity and duration of exercise
      • Time of day
      • Clothing or uniform requirements
      • Playing surface for radiant and conductive heat exchange (i.e., grass vs synthetic fields)

Comorbidity Considerations

Obesity

  • General
    • Obesity is associated with increased risk of HRI[22]
    • Increased body mass results in reduced surface area necessary for heat dissipation via evaporation
    • Metabolic exothermia increases with body weight
    • No specific restriction are neaded for obese idividuals
    • However, they should be monitored closely for signs of heat illness

Sickle Cell Trait

  • General
    • Stressors, including exercise and heat illness, predispose HgbS patients to a sickling crisi
    • There are reports of death in SST athletes related to exertional heat stroke[23]
    • Risk is increased by dehydration, extreme heat and exercise at altitude
    • Patients with HgbS should be monitored closely to maintain hydration, especially in heat or at altitude
  • Note: Sickle Cell Disease patients are unlikely to participate in athletics

Return To Play

See Also

References

  1. ↑ 1.0 1.1 Kerr ZY, Casa DJ, Marshall SW, Comstock RD. Epidemiology of exertional heat illness among U.S. high school athletes. Am J Prev Med. 2013;44(1):8–14.
  2. ↑ 2.0 2.1 Armed Forces Health Surveillance Bureau. Update: heat illness, active component, U.S. Armed Forces, 2018. MSMR. 2018;25(4):6–10.
  3. ↑ 3.0 3.1 Hess JJ, Saha S, Luber G. Summertime acute heat illness in U.S. emergency departments from 2006 through 2010: analysis of a nationally representative sample [published correction appears in Environ Health Perpsect. 2014;122(11):A293]. Environ Health Perspect. 2014;122(11):1209–1215.
  4. ↑ Jardine DS. Heat illness and heat stroke [published correction appears in Pediatr Rev. 2007;28(12):469]. Pediatr Rev. 2007;28(7):249–258.
  5. ↑ CDC Infographic: https://www.cdc.gov/pictureofamerica/pdfs/picture_of_america_heat-related_illness.pdf
  6. ↑ Mueller, F., and R. Cantu. "Catastrophic sports injury research: twenty-sixth annual reports." (2008).
  7. ↑ Kravchenko, Julia, et al. "Minimization of heatwave morbidity and mortality." American journal of preventive medicine 44.3 (2013): 274-282.
  8. ↑ NOAA, NWS. "Weather fatalities 2017." (2018).
  9. ↑ Coris, EE , Walz, SM , Duncanson, R. , Ramirez, AM , Roetzheim, RG Heat illness symptom index (HISI): a novel instrument for the assessment of heat illness in athletes. South Med J.2006; 99:340–345.
  10. ↑ Gaffin, SL , Moran, DS Pathophysiology of heat-related illnesses. In: Auerbach, PS , ed. Wilderness Medicine. 4th ed. St Louis, Mo: Mosby; 2001:240–281.
  11. ↑ Glazer, JL Management of heatstroke and heat exhaustion. Am Fam Phys.2005;71:2133–2140.
  12. ↑ Booth, John N., et al. "Hyperthermia deaths among children in parked vehicles: an analysis of 231 fatalities in the United States, 1999–2007." Forensic science, medicine, and pathology 6.2 (2010): 99-105.
  13. ↑ Heat-related deaths — United States, 1999–2003. MMWR Morb Mortal Wkly Rep 2006;55:796-798.
  14. ↑ Roberts, William O., et al. "ACSM expert consensus statement on exertional heat illness: recognition, management, and return to activity." Current sports medicine reports 20.9 (2021): 470-484.
  15. ↑ Hajat, Shakoor, Madeline O'Connor, and Tom Kosatsky. "Health effects of hot weather: from awareness of risk factors to effective health protection." The Lancet 375.9717 (2010): 856-863.
  16. ↑ 16.0 16.1 Howe, Allyson S., and Barry P. Boden. "Heat-related illness in athletes." The American Journal of Sports Medicine 35.8 (2007): 1384-1395.
  17. ↑ Taylor NA. Human heat adaptation. Compr. Physiol. 2014; 4:325–65.
  18. ↑ Périard JD, Racinais S, Sawka MN. Adaptations and mechanisms of human heat acclimation: applications for competitive athletes and sports. Scand. J. Med. Sci. Sports. 2015; 25(Suppl. 1):20–38.
  19. ↑ Sawka MN, Young AJ, Latzka WA, et al. Human tolerance to heat strain during exercise: influence of hydration. J. Appl. Physiol. 1992; 73:368–75.
  20. ↑ Cheuvront SN, Kenefick RW. Dehydration: physiology, assessment, and performance effects. Compr. Physiol. 2014; 4:257–85.
  21. ↑ Kulka, TJ , Kenney, WL Heat balance limits in football uniforms. Physician and Sportsmedicine.2002;30:29–39.
  22. ↑ Wyndham, CH Heat stroke and hyperthermia in marathon runners. Ann NY Acad Sci.1977;301:128–138.
  23. ↑ Pretzlaff, RK Death of an adolescent athlete with sickle cell trait caused by exertional heat stroke. Pediatr Crit Care Med.2002;3:308–310.
Created by:
John Kiel on 13 June 2019 05:29:54
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Last edited:
31 August 2022 15:22:33
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