Evaluation of Heat Illness. Physiology of Temperature Regulation HypothalamusHypothalamus –Center for thermal regulation –integrates input from thermal.

Evaluation of Evaluation of Heat Illness Heat Illness

Physiology of Temperature Physiology of Temperature RegulationRegulation

• HypothalamusHypothalamus– Center for thermal Center for thermal

regulation regulation – integrates input from integrates input from

thermal receptorsthermal receptors– Sends autonomic Sends autonomic

impulses to increase impulses to increase vasodilation / vasodilation / vasoconstriction to vasoconstriction to periphery and cause periphery and cause sweating / shiveringsweating / shivering

Body TemperatureBody Temperature

• Determined by balance Determined by balance between heat production between heat production (BMR, muscular activity) (BMR, muscular activity) and heat lossand heat loss

• Environmental conditions Environmental conditions can make 98.6° difficult can make 98.6° difficult to maintainto maintain

Mechanisms to Promote Mechanisms to Promote Heat LossHeat Loss

• ConductionConduction• ConvectionConvection• EvaporationEvaporation• RadiationRadiation

S = M +/- R +/- K +/- Cv - ES = M +/- R +/- K +/- Cv - E

AssumptionsAssumptions

• Convection, and radiation are very Convection, and radiation are very effective when external temp is lower effective when external temp is lower than 87° than 87°

• If external temp is higher than body If external temp is higher than body temp, heat transfer is reversed temp, heat transfer is reversed

• Evaporation becomes primary methodEvaporation becomes primary method• The more humidity, the less effective The more humidity, the less effective

evaporation becomes. (Big decrease evaporation becomes. (Big decrease when >60%).when >60%).

Sweat RatesSweat Rates

• Up to 2 liters per hourUp to 2 liters per hour• 2% body weight impairs 2% body weight impairs

performanceperformance• Thirst not a good Thirst not a good

indicator of hydration indicator of hydration statusstatus

• 1L of sweat = 1.25L 1L of sweat = 1.25L ingested beverageingested beverage

• < 50% of fluid lost is < 50% of fluid lost is typically replaced typically replaced

Electrolyte LossesElectrolyte Losses

• Na+, Cl-, K+, Mg+Na+, Cl-, K+, Mg+• Na – main one – Na – main one –

muscle crampsmuscle cramps• Typical American Typical American

diet replaces most diet replaces most electrolyteselectrolytes

Heat Exposure Syndromes Heat Exposure Syndromes

• TraditionalTraditional– Heat CrampsHeat Cramps– Heat ExhaustionHeat Exhaustion– Heat StrokeHeat Stroke

• New ClassificationsNew Classifications– Heat SyncopeHeat Syncope– Exertional Exertional

HyponatremiaHyponatremia

Heat CrampsHeat Cramps

• Water loss vs Water loss vs Electrolyte loss?Electrolyte loss?

• Athletes most at Athletes most at risk have a Hxrisk have a Hx

• Extremities & Extremities & abdominalsabdominals

Rx for Heat Cramps Rx for Heat Cramps

• Fluid replacement w/ Fluid replacement w/ NaNa

• Gentle Stretching Gentle Stretching and Massageand Massage

• Lie Down to increase Lie Down to increase blood flow to the legsblood flow to the legs

• IceIce

Heat SyncopeHeat Syncope

• AKA “Orthostatic AKA “Orthostatic Dizziness”Dizziness”

• Caused by peripheral Caused by peripheral vasodilation, postural vasodilation, postural pooling of blood, pooling of blood, decreased venous decreased venous return and Qreturn and Q

• 11stst 5 days before 5 days before acclimatized acclimatized

Heat Syncope RecognitionHeat Syncope Recognition

• Brief episode of dizziness associated Brief episode of dizziness associated with tunnel vision, pale or sweaty skin, with tunnel vision, pale or sweaty skin, decreased pulsedecreased pulse

• Normal Temp (97-104°)Normal Temp (97-104°)

Heat ExhaustionHeat Exhaustion

• AKA “Heat Prostration”AKA “Heat Prostration”• Caused by inadequate Caused by inadequate

CV response CV response – brain vs skin vs brain vs skin vs

musclesmuscles– Dehydration Dehydration

decreases blood decreases blood volumevolume

Heat Syncope RxHeat Syncope Rx

• ShadeShade• Monitor VitalsMonitor Vitals• Elevate LegsElevate Legs• RehydrateRehydrate

Signs and Symptoms of Signs and Symptoms of Heat ExhaustionHeat Exhaustion

• Hypovolemic ShockHypovolemic Shock• Sx vary in severity and numberSx vary in severity and number• Weakness, fatigue, dizziness, headache, loss Weakness, fatigue, dizziness, headache, loss

of appetite, nausea, pallor, profuse sweating, of appetite, nausea, pallor, profuse sweating, vomiting, urge to defecate, syncope, thirsty, vomiting, urge to defecate, syncope, thirsty, irritableirritable

• Can be difficult to distinguish from Heat Can be difficult to distinguish from Heat Stroke w/ out rectal tempStroke w/ out rectal temp

• Body Core Temp ranges from 97-104°Body Core Temp ranges from 97-104°• Assess cognitive skills to rule more serious Assess cognitive skills to rule more serious

conditionsconditions

Rx for Heat ExhaustionRx for Heat Exhaustion

• Rest in CoolRest in Cool• Fluid ReplacementFluid Replacement

– IngestingIngesting– IVIV

• Electrolyte Electrolyte ReplacementReplacement

• Supine PostureSupine Posture• Remove excessive Remove excessive

clothingclothing• Cold Buckets / FansCold Buckets / Fans

Heat StrokeHeat Stroke

• Body’s cooling Body’s cooling mechanisms have failed mechanisms have failed leading to hyperpyrexia leading to hyperpyrexia (body temp > 104°)(body temp > 104°)

• Anhidrosis – body stops Anhidrosis – body stops sweatingsweating

• Causes damage to CNS Causes damage to CNS and internal organsand internal organs

• May develop suddenly or May develop suddenly or progress from heat progress from heat exhaustionexhaustion

• Medical EmergencyMedical Emergency

Signs and Symptoms of Signs and Symptoms of Heat StrokeHeat Stroke

• Hot, dry skinHot, dry skin• Decreasing BPDecreasing BP• Rapid, full pulse Rapid, full pulse

becomes rapid, weakbecomes rapid, weak• Vomiting, diarrhea, Vomiting, diarrhea,

seizures, comaseizures, coma• Poor cognitive Poor cognitive

functionfunction• Multiple organ Multiple organ

failurefailure

Conditions Resulting from Conditions Resulting from Heat StrokeHeat Stroke

• Lactic AcidosisLactic Acidosis

• Hyperkalemia Hyperkalemia (excessive K+)(excessive K+)

• Renal FailureRenal Failure

• Disseminated Disseminated Intervascular Intervascular CoagulatonCoagulaton

Rx for Heat StrokeRx for Heat Stroke

• Cooling immediately – Cooling immediately – immerse in cold bath immerse in cold bath (35-59 degrees) to (35-59 degrees) to reduce body temp to < reduce body temp to < 100°100°– Remove from pool Remove from pool

when body temp when body temp reaches 101°reaches 101°

• Use wet towels /ice Use wet towels /ice bags and fanning in bags and fanning in transport to hospitaltransport to hospital

• Treat for shockTreat for shock

Exertional HyponatremiaExertional Hyponatremia

• Rare?Rare?• Low serum-Na level (< 130mmol/L)Low serum-Na level (< 130mmol/L)• Ingest too much water vs ingest too little Na?Ingest too much water vs ingest too little Na?• Sx – disorientation, headache, vomiting, Sx – disorientation, headache, vomiting,

lethargy, swelling of extremities, pulmonary lethargy, swelling of extremities, pulmonary and cerebral edema, seizuresand cerebral edema, seizures

• Results in death if not treated by rehydrating Results in death if not treated by rehydrating w/ fluids w/ Naw/ fluids w/ Na

Reducing Risk of Heat IllnessReducing Risk of Heat Illness

• Pre-participation Pre-participation Physical / Screening Physical / Screening

• Early Recognition of Early Recognition of SxSx

• ConditioningConditioning• AcclimatizationAcclimatization

– 4–7 days vs 10-14 days 4–7 days vs 10-14 days vs months?vs months?

– After 6 weeks able to After 6 weeks able to produce 2.5x normal produce 2.5x normal amount of sweatamount of sweat

– Diminishes by day 6 of Diminishes by day 6 of inactivityinactivity

Reducing Risk (con’t)Reducing Risk (con’t)

• Educate players and Educate players and coachescoaches

• Diet – extra Na+Diet – extra Na+• Rest and DigestRest and Digest• Monitor urine color Monitor urine color

and amount and amount • Weigh in and outWeigh in and out• Clothing / Equipment Clothing / Equipment

modificationsmodifications

Reducing Risk (con’t)Reducing Risk (con’t)

• Stay well Stay well hydrated hydrated (NATA Position (NATA Position Statement: Fluid Replacement )Statement: Fluid Replacement )

– Pre: 17-20oz, 2-3 Pre: 17-20oz, 2-3 hours before and hours before and 7-10oz.7-10oz.

– 20 min before20 min before– During: 7-10oz During: 7-10oz

every 20 minevery 20 min– Replace lost fluidReplace lost fluid

Reducing Risk Reducing Risk (con’t)(con’t)

– Beverage Temp Beverage Temp 50-59°50-59°

– Beverage ChoiceBeverage Choice• WaterWater• 6-8% CHO solution 6-8% CHO solution

if longer than 45 if longer than 45 minsmins

• No Caffeine, No Caffeine, alcoholalcohol

• .3-.7g/L Salt (esp .3-.7g/L Salt (esp 11stst 3-5 days) 3-5 days)

Reducing Risk (con’t)Reducing Risk (con’t)

• Fans Fans • ShadeShade• Cold bucketsCold buckets• Cold TubCold Tub• ThermometerThermometer• BP CuffBP Cuff• TelephoneTelephone

Predisposing Medical Predisposing Medical Conditions for Heat IllnessConditions for Heat Illness

• Sickle Cell Trait – carry Sickle Cell Trait – carry less O2less O2

• Cystic Fibrosis Trait – Cystic Fibrosis Trait – increases salt loss in increases salt loss in sweatsweat

• Arteriosclerotic Vascular Arteriosclerotic Vascular Disease – thicker arterial Disease – thicker arterial walls decrease blood walls decrease blood flowflow

• Scleroderma – skin Scleroderma – skin disorder that increases disorder that increases sweatingsweating

Predisposing Medical Conditions Predisposing Medical Conditions for Heat Illness for Heat Illness (con’t)(con’t)

• Drug / Supplement Use – Drug / Supplement Use – EphedraEphedra– DiureticsDiuretics– Antidepressants decrease Antidepressants decrease

sweatingsweating– Beta blockers reduce skin Beta blockers reduce skin

blood flowblood flow– Antihistamines constrict Antihistamines constrict

blood vessels.blood vessels.

Recommendations Recommendations

National Weather Service National Weather Service RecommendationsRecommendations

• Cease activity Cease activity when Heat index when Heat index is over 105°is over 105°

• Heat index only Heat index only includes includes temperature and temperature and humidityhumidity

Instruments to Evaluate Instruments to Evaluate Hot/Humid EnvironmentsHot/Humid Environments

WBGT Sling/Digital PyschomoterWBGT Sling/Digital Pyschomoter

WBGT=.1(DBT)+ .7(WBT)+.2(GT)WBGT=.1(DBT)+ .7(WBT)+.2(GT)

Temperature & Humidity

Temperature, humidity, radiant heat, and air movementTemperature, humidity, radiant heat, and air movement

WBGT = .7(WBT) + .3(DBT)

Event and Practice GuidelinesEvent and Practice Guidelines

Arnheim & Prentice, 1993Arnheim & Prentice, 1993– Watch the ObeseWatch the Obese

• 80-90 degrees & < 70% humidity80-90 degrees & < 70% humidity– Take a 10 min rest every hour, change t-shirts when Take a 10 min rest every hour, change t-shirts when

wet, watch all athleteswet, watch all athletes• 80-90 degrees and > 70% or 90-100 degrees and 80-90 degrees and > 70% or 90-100 degrees and

< 70%< 70%– Suspend practice Suspend practice

• > 100 degrees or > 90 degrees & humidity over > 100 degrees or > 90 degrees & humidity over 70%70%

WBGT > 90 No training, skull sessions

NATA Position Statement Activity Modification Guidelines Using WBGT

Event and Practice GuidelinesEvent and Practice Guidelines

(NATA Position Statement: (NATA Position Statement: Exertional Heat, 2002)Exertional Heat, 2002)

• Wet Bulb Globe TemperatureWet Bulb Globe Temperature– WBGT > 82, reschedule, if possibleWBGT > 82, reschedule, if possible

Even in the South? We’d never practice!Even in the South? We’d never practice!

DisclaimerDisclaimer• ““Certified athletic trainers work in a variety of Certified athletic trainers work in a variety of

professional and geographic settings….. obviously the professional and geographic settings….. obviously the ATC in Florida will adapt the recommendations to his or ATC in Florida will adapt the recommendations to his or her environment, while the ATC in Maine will make her environment, while the ATC in Maine will make different adjustments.”different adjustments.” - Casa - Casa

• ““Athletic trainers should recognize that temperature Athletic trainers should recognize that temperature ranges might vary widely based upon geographic ranges might vary widely based upon geographic regions. Athletic trainers may practice in regions, such as regions. Athletic trainers may practice in regions, such as the southeastern United States, where the WBGT is the southeastern United States, where the WBGT is routinely in the high or extreme or hazardous level of risk routinely in the high or extreme or hazardous level of risk throughout a significant part of the year. In these throughout a significant part of the year. In these regions, while it may not be practical to reschedule or regions, while it may not be practical to reschedule or delay events, the athletic trainer must recognize that the delay events, the athletic trainer must recognize that the level of risk is high and take appropriate steps to reduce level of risk is high and take appropriate steps to reduce risk.”risk.” – NATA – NATA

NATA Position Statement NATA Position Statement Activity Modification Guidelines Activity Modification Guidelines using Temp and Humidityusing Temp and Humidity

• Add 5 degrees to temp Add 5 degrees to temp on bright sunny days on bright sunny days bwtn 10 and 4bwtn 10 and 4

• Lt of triangles - Full gearLt of triangles - Full gear• Rt of circles - walk-thru Rt of circles - walk-thru • Btwn squares and circles Btwn squares and circles

- break every 15-20 min - break every 15-20 min & shorts only& shorts only

• Bwtn triangles and Bwtn triangles and squares - break every squares - break every 20-30 min & helmet and 20-30 min & helmet and shoulder padsshoulder pads

Risk of Heat Exhaustion in Risk of Heat Exhaustion in Hot/Humid EnvironmentsHot/Humid Environments

Take a look at the Inter-Take a look at the Inter-Association Task Force Association Task Force Heat Illness Consensus Heat Illness Consensus Statement Statement

Inter-Association Task Force onInter-Association Task Force onExertional Heat IllnessesExertional Heat IllnessesConsensus Statement Consensus Statement (June 2004)(June 2004)

These guidelines were established to increase safety and These guidelines were established to increase safety and performance for individuals engaged in physical activity, performance for individuals engaged in physical activity, especially in warm and hot environments. The risks associated especially in warm and hot environments. The risks associated with exercise in the heat are well documented, but policies and with exercise in the heat are well documented, but policies and procedures often do not reflect current state-of-the-art procedures often do not reflect current state-of-the-art knowledge. Many cases of exertional heat illness are knowledge. Many cases of exertional heat illness are preventable and can be successfully treated if onsite personnel preventable and can be successfully treated if onsite personnel identify the condition and implement appropriate care in a identify the condition and implement appropriate care in a timely manner. Strategies to optimize proper care of timely manner. Strategies to optimize proper care of dehydration, exertional heat stroke (EHS), heat exhaustion, dehydration, exertional heat stroke (EHS), heat exhaustion, heat cramps and exertional hyponatremia are presented here. heat cramps and exertional hyponatremia are presented here. This consensus statement was developed by medical / This consensus statement was developed by medical / scientific experts experienced in the prevention, recognition scientific experts experienced in the prevention, recognition and treatment of exertional heat illnesses.and treatment of exertional heat illnesses.

Return to Play Criteria for Return to Play Criteria for Dehydration Dehydration

• A nauseated or vomiting athlete should A nauseated or vomiting athlete should seek medical attention to replace fluids seek medical attention to replace fluids via an intravenous line.via an intravenous line.

• Return-to-Play ConsiderationsReturn-to-Play Considerations– If the degree of dehydration is minor and the If the degree of dehydration is minor and the

athlete is symptom free, continued athlete is symptom free, continued participation is acceptable. The athlete must participation is acceptable. The athlete must maintain hydration status and should maintain hydration status and should receive periodic checks from onsite medical receive periodic checks from onsite medical personnel.personnel.

Return-to-Play Return-to-Play Considerations After Heat Considerations After Heat StrokeStroke

Physiological changes may occur after an episode of EHS. Physiological changes may occur after an episode of EHS. Heat tolerance may be compromised. Heat tolerance may be compromised.

The following guidelines are recommended for return-to-The following guidelines are recommended for return-to-play after EHS:play after EHS:

• Physician clearance: Avoid exercise until completely Physician clearance: Avoid exercise until completely asymptomatic & lab tests are normal.asymptomatic & lab tests are normal.

• Severity of the incident should dictate the length of Severity of the incident should dictate the length of recovery time.recovery time.

• • Avoid exercise for the minimum of 1 week after release Avoid exercise for the minimum of 1 week after release from medical care.from medical care.

• • Gradual return to physical activity. Gradual return to physical activity.

Return-to-Play Return-to-Play Considerations After Heat Considerations After Heat Stroke Stroke (con’t)(con’t)

Type and length of exercise should be determined by the athlete's Type and length of exercise should be determined by the athlete's physician and might follow this pattern:physician and might follow this pattern:

1. Easy-to-moderate exercise in a climate controlled1. Easy-to-moderate exercise in a climate controlledenvironment for several days, followed by strenuous exercise in a environment for several days, followed by strenuous exercise in a

climate-controlled environment for several days.climate-controlled environment for several days.

2. Easy-to-moderate exercise in heat for several days, followed by 2. Easy-to-moderate exercise in heat for several days, followed by strenuous exercise in heat for several days.strenuous exercise in heat for several days.

3. (If applicable) Easy-to-moderate exercise in heat with 3. (If applicable) Easy-to-moderate exercise in heat with equipment for several days, followed by strenuous exercise in equipment for several days, followed by strenuous exercise in heat with equipment for several days.heat with equipment for several days.

Return to Play Criteria for Return to Play Criteria for Heat ExhaustionHeat Exhaustion

• No Sx and fully hydrated.No Sx and fully hydrated.• Recommend physician clearance or, Recommend physician clearance or,

at minimum, a discussion w/ at minimum, a discussion w/ supervising physician before return.supervising physician before return.

• Rule out underlying condition or Rule out underlying condition or illness that predisposed athlete for illness that predisposed athlete for continued problems.continued problems.

Return to Play Criteria for Return to Play Criteria for Heat Exhaustion Heat Exhaustion (con’t)(con’t)

• Avoid intense practice in heat until at least the Avoid intense practice in heat until at least the next day to ensure recovery from fatigue & next day to ensure recovery from fatigue & dehydration. (In severe cases, intense practice dehydration. (In severe cases, intense practice in heat should be delayed for > 1 day.)in heat should be delayed for > 1 day.)

• If underlying cause was lack of acclimatization If underlying cause was lack of acclimatization and/or fitness level, correct this problem before and/or fitness level, correct this problem before athlete returns to full-intensity training in heat athlete returns to full-intensity training in heat (especially in sports with equipment).(especially in sports with equipment).

Return to Play Guidelines Return to Play Guidelines for Heat Crampsfor Heat Cramps

• Perform at the level needed for Perform at the level needed for successful participation?successful participation?

• Review Review – DietDiet– Rehydration practicesRehydration practices– Electrolyte consumptionElectrolyte consumption– Fitness statusFitness status– Level of acclimatization Level of acclimatization – Use of dietary supplementsUse of dietary supplements

Return to Play Criteria for Return to Play Criteria for Exertional HyponatriemaExertional Hyponatriema

• Physician clearance Physician clearance

• Mild cases, activity can resume a few Mild cases, activity can resume a few days after completing an educational days after completing an educational session on establishing an individual-session on establishing an individual-specific hydration protocolspecific hydration protocol– ensures proper amount and type of ensures proper amount and type of

beverages and meals are consumed before, beverages and meals are consumed before, during and after physical activity (see Table during and after physical activity (see Table 2).2).

ReferencesReferences• Arnheim D.D. & Prentice W.E. (1993). Principles of Athletic Training. (8Arnheim D.D. & Prentice W.E. (1993). Principles of Athletic Training. (8 thth

ed.) St. Louis: Mosby-Year Book.ed.) St. Louis: Mosby-Year Book.

• American Academy of Orthopaedic Surgeons. (1999). American Academy of Orthopaedic Surgeons. (1999). Athletic Training Athletic Training and Sports Medicineand Sports Medicine. (3. (3rdrd ed.) ed.)

• Binkley HM, Beckett, Casa DJ, Kleiner DM, Plummer PE. (2002). National Binkley HM, Beckett, Casa DJ, Kleiner DM, Plummer PE. (2002). National Athletic Trainers’ Association Position Statement: exertional heat Athletic Trainers’ Association Position Statement: exertional heat illness. Journal of Athletic Training, 37(3):329-343. illness. Journal of Athletic Training, 37(3):329-343.

• Casa DJ, Armstrong LE, Hillman SK, Montain SJ, Reiff RV, Rich BS, Casa DJ, Armstrong LE, Hillman SK, Montain SJ, Reiff RV, Rich BS, Roberts WO, Stone JA. (2000). National Athletic Trainers’ Association Roberts WO, Stone JA. (2000). National Athletic Trainers’ Association Position Statement: fluid replacement for athletes. Journal of Athletic Position Statement: fluid replacement for athletes. Journal of Athletic Training, 35(2):212-224.Training, 35(2):212-224.

• Inter-Association Task Force on Exertional Heat Illness Consensus Inter-Association Task Force on Exertional Heat Illness Consensus Statement (2004). www.nata.orgStatement (2004). www.nata.org