Morteza Khodaee, MD, MPH August 2, 2013

Transcription

1 Morteza Khodaee, MD, MPH August 2, 2013

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3 Objectives Epidemiology Thermoregulation Risk Factors Clinical presentations Treatment Prevention

4 Epidemiology ~9,000 high school athletes treated for EHI annually 31 high school football players have died from heat stroke since 1995 Rates of exertional heat illness among U.S. high school athletes, by year

5 Epidemiology Rates of EHI among U.S. high school football athletes, by state

6 Epidemiology Rates of EHI among U.S. high school athletes in sports other than football, by state

7 Epidemiology Approximately 240 deaths/year in US Most occur in >50 yo and not related to physical activities

8 Epidemiology Heat illness (HI) is the leading cause of death and disability during participation in US high school and collegiate athletics ~5,946 persons were treated in US EDs each year for a heat illness sustained while participating in a sport or recreational activity Estimated annual rate of 2.0 ED visits per 100,000 population.

9 Epidemiology Non-fatal HI Work-related, including military training HI were excluded

10 Epidemiology Sports specific (non-fatal)

11 Thermoregulation Conduction Direct transfer of heat from a warmer surface to a cooler surface Evaporation Perspiration is an evaporative mechanism that is dependent on sweat production and water vapor pressure Radiation The process by which the body gains or loses heat without direct contact Convection Exchanges heat with the surrounding air

12 Pediatric thermoregulation contrary to previous thinking, youth do not have less effective thermoregulatory ability, insufficient cardiovascular capacity, or lower physical exertion tolerance compared with adults during exercise in the heat when adequate hydration is maintained. Accordingly, besides poor hydration status, the primary determinants of reduced performance and exertional heat-illness risk in youth during sports and other physical activities in a hot environment include undue physical exertion, insufficient recovery between repeated exercise bouts or closely scheduled same-day training sessions or rounds of sports competition, and inappropriately wearing clothing, uniforms, and protective equipment that play a role in excessive heat retention. COUNCIL ON SPORTS MEDICINE AND FITNESS AND COUNCIL ON SCHOOL HEALTH. Policy Statement--Climatic Heat Stress and Exercising Children and Adolescents. Pediatrics Aug 8

13 Risk Factors Age >65 yrs or <15 yrs Cognitive impairment Heart and lung diseases Limited access to air-conditioning Mental illness Obesity Physical disabilities/impaired mobility Poor fitness level Sickle cell trait Strenuous outdoor activity during hottest daytime hours Urban residence or living on higher floors

14 Medications and Substances that Contribute to Heat-Related Illness Alcohol α-adrenergic agonists Amphetamines Anticholinergics Antihistamines Benzodiazepines β-blockers Calcium channel blockers Cocaine Diuretics Ephedra-containing supplements Laxatives Neuroleptics Phenothiazines Stimulants Thyroid receptor agonists Tricyclic antidepressants

15 Heat-Related Illness Mild Heat-Related Illness (usually core temperature < 104 F or <40 C) Heat edema Heat rash Heat cramps Heat-related Syncope Heat exhaustion Heat stroke Core temperature >104 F (40 C) in the presence of CNS disturbances

16 Heat Illness

17 Heat Edema Peripheral vasodilation to heat loss leads to pooling of interstitial fluid in the distal extremities vascular hydrostatic pressure and 3 rd spacing of IV fluid into the surrounding soft tissue More commonly seen in older adults who enter a tropical climate without proper acclimatization Altitude?

18 Heat Rash (Miliaria rubra) Pinpoint papular erythematous, often intensely pruritic, eruption in areas covered with clothing Commonly presents in the waist or over highly sweaty areas such as the trunk or groin

19 Heat Rash (Miliaria rubra) Usually self-limited

20 Heat Syncope Peripheral vasodilation & venous pooling orthostatic hypotension Prolonged standing after significant exertion and rapid change in body position after exertion Athletes with heat syncope tend to recover their mental status quickly once supine

21 Heat Syncope

22 Exercise-Associated Muscle Cramps (Heat Cramps) Etiology not completely understood Predisposing factors: Exercise-induced muscle fatigue Body water loss Large sweat Na + loss More common in long-duration, high-intensity events

23 Exercise-Associated Muscle Cramps Treatment Rest (Heat Cramps) Prolonged stretch with the muscle groups at full length Oral NaCl ingestion in fluids or food Intravenous NS fluids provide rapid relief from severe EAMC in some cases Calcium salts, NaCO3, quinine, and dextrose have not produced consistent benefits when treating EAMC

24 Heat Exhaustion Inability to continue to exercise, occurs with heavy exertion in all temperatures and may or may not be associated with physical collapse Several lines of evidence suggest that heat exhaustion results from the central fatigue that induces widespread peripheral vascular dilation and associated collapse The most common heat related disorder observed in active populations

25 Heat Exhaustion

26 Heat Exhaustion Predisposing Factors BMI > 27 kg/m2 Work during the hottest months of the year Elevated urine specific gravity, hematocrit, hemoglobin, or serum osmolality suggesting inadequate fluid intake An air temperature >33 C and an air velocity < 2.0 m/s Otis Hudson collapsed as he was lining up for a play in camp in August

27 Heat Exhaustion The signs and symptoms of heat exhaustion are neither specific nor sensitive Headache Weakness Dizziness Goose flesh Nausea/vomiting, Diarrhea Irritability Loss of coordination

28 Signs Low BP Heat Exhaustion Elevated pulse and respiratory rates Patient appears sweaty, pale, and ashen Normal mentation

29 Treatment Heat Exhaustion Moving to a shaded or air conditioned area Remove excess clothing Place in the supine position with legs elevated Monitor VS and rectal temp Close CNS status monitoring Cooling therapy Oral fluids are preferred May need IV fluids

30 Exertional Heat Stroke Exertional heatstroke (EHS) is defined by hyperthermia (core body temperature >40ºC) associated with CNS disturbances and multiple organ system failure

31 Exertional Heat Stroke Almost all EHS patients exhibit sweat-soaked and pale skin at the time of collapse, as opposed to the dry, hot, and flushed skin that is described in the presentation of non-exertion-related (classic) heatstroke Multiple stressors such as a sudden increase in physical training, obesity, low physical fitness level, lengthy initial exposure to heat, vapor barrier protective clothing, sleep deprivation, inadequate hydration, and poor nutrition risk of EHS

32 Exertional Heat Stroke EHS is a true emergency and requires immediate recognition and treatment

33 Core Body Temp Measurement

34 Rectal Temperature Assessment The only available and accurate way to measure the core body temp At least cm past the anal sphincter

35 Temperature Assessment Ingestible thermistor Ingested before the game/practice Costly Sensor malfunction

36 Treatment of Heat Stroke Activate EMS immediately Remove from play Remove uniform Rapid cooling High flow O 2, pulse ox, intubate prn IV NS cc/hr Cardiac monitor Continuous core temperature monitoring Transfer to the ED

37 Exertional Heat Stroke Treatment Rapid cooling Cold water immersion provides the fastest whole body cooling rate and the lowest morbidity and mortality for EHS (LOE:A)

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39 Prognosis of Heat Stroke 90% survival with proper treatment Morbidity directly related to duration of hyperthermia Poor prognosis Temp > 41 o C Prolonged hyperthermia Hyperkalemia, ARF, elevated LFTs Persistence of coma with normal temperature

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41 Predisposing Factors for HRI Greatest risk is when Wet-Bulb Globe Temp exceeds 28 C (82 F) High intensity exercise (>75% V-O 2 Max ) Exercise lasts > 1 hour Football: most episodes occur during first 4 days of preseason practice

42 The Wet Bulb Globe Temperature, which takes into account temperature, humidity, and radiant thermal energy, is the preferred method for assessing weather conditions that precipitate heat-related illness

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44 Heat Index Chart

45 Preventing Heat Illness Educate players and coaches on signs and symptoms of heat illness Do not restrict dietary sodium intake (eat normal meals) Acclimatization

46 Preventing Heat Illness Appropriate hydration very important Obtain euhydrotic weight as reference One hour prior to practice/game, athlete should ingest ~ 2% est. water weight of hypotonic CHO solution (6%)

47 Preventing Heat Illness After practice/game Reweigh athlete Drink at least 1/2 weight lost within first hour Other measures Early morning or late afternoon practices Meal schedules (addition of salt and fluids)

48 NCAA Acclimatization Period 5 day acclimatization period at beginning of fall preseason practice Maximum of one practice per day Followed by practice schedule Allows athletes to acclimate to heat, humidity, equipment, increased intensity of exercise Body becomes better at responding to heat within a few days

49 Acclimatization Period 10 to 14 days of exercise training in the heat will improve heat acclimatization and reduce the risk of EHS (LOE: C) National Athletic Trainer s Association: Recommends 14 day acclimatization period

50 Proposed recommendations for the return to training and competition Refrain from exercise for at least 7 d following release from medical care Follow up in about 1 wk for physical exam and repeat lab testing or diagnostic imaging of affected organs that may be indicated, based on the physician`s evaluation When cleared for activity, begin exercise in a cool environment and gradually increase the duration, intensity, and heat exposure for 2 wk to acclimatize and demonstrate heat tolerance. If return to activity is difficult, consider a laboratory exercise-heat tolerance test about one month post-incident Clear the athlete for full competition if heat tolerance exists after 2 4 wk of training

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