Exertional Heat StrokeRebecca M. Northway, MD

Internal Medicine-Pediatrics

Primary Care Sports Medicine

October 2, 2019

• Defining and differentiating types of heat illness

• Discuss treatment

• Prevention of future heat illness

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Objectives

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Incidence

• Most common causes of death in high school athletes:– Head/neck trauma

– Cardiac disorders

– Heat illness (99% during practice)

• Heat stroke is 3rd leading cause of mortality

• Leading cause of preventable death in high school athletes – From 2002-2012 there have

been 31 heat stroke deaths in HS Football - National Center for Catastrophic Sports Injury Research

Heat Production & Thermal Regulation

• Physiological responses depend on the environment

• Intended to allow the body to maintain a constant internal temperature

• If exposures are prolonged and gradual, productive adaptations occur

• Outside a narrow range of internal core temperature essential body functions break down

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Mechanisms of Heat Production

• Normal Thermal Exchange– Exogenous

• Radiation- between 2 objects not in contact with one another

• Convection- secondary to air moving across a warmer/cooler object

• Conduction- between 2 objects in contact with one another

• Evaporation- heat loss when water is converted to vapor

• Contributors– WBGT

– Clothing and Equipment

Mechanisms of Heat Production

• Endogenous

– From an energy standpoint the body is inefficient

• Muscles produce 20x more energy at work than at rest

• 75% energy used in muscle activity is dissipated as heat

• To prevent dangerous temp elevation, runners need to loose 90% of heat generated

– Dehydration: +0.3 °C (32°F)/1L loss

• Impaired heat dissipation

– Increase BMI

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• Classic:

– High environmental temperature

– Exogenous heat load overwhelms body to adapt (heat waves)

– Those at risk:

• Sleeping infants, unattended children in automobiles, disabled, elderly

• Certain medications increase risk

• Geographical and seasonal

• Exertional:

– Elevated environmental temperature combined with strenuous exercise

– Exogenous heat load combines w/ endogenous heat load to overwhelm body’s heat dissipation mechanisms

– Those at risk:

• Adolescents and adults more likely than young children

– Highly motivated athletes, soldiers, laborers

– Dehydration

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Classic vs. Exertional

Basic Principles

• 3 basic principals to assure favorable outcomes

– 1. Rapid assessment with rectal temperature

– 2. Immediate on site cooling until 102°F (38.8°C)

– 3. Use of cold water immersion for cooling

• 100% survival without major sequelae

– Cool 1st, Transport 2nd

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• Poor preparation– Not heat-acclimatized

– Inadequate pre-hydration

– Sleep deprived/overtraining

– Poor fitness

• Type of Exercise– Intensity of Exercise

– Duration/frequency of Exercise

– Environmental Conditions

– Clothing

• Inadequate Acclimatization or aerobic fitness

• History of EHI

• Knowledge of EHI

• Sickle Cell Trait

• Excess body fat

• Febrile condition or illness

• Inadequate hydration

• Medications:

– Diuretics

– Antihistamines

– Decongestants

– Stimulants or ETOH/drugs

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Potential Risk Factors For Exertional Heat Illness

Heat Fatigue and Cramps

• Heat Fatigue- fatigue, weakness, headache

• Responds to cessation of activity, moving out of direct sun, oral sodium containing fluids

• Heat Cramps- Acute painful involuntary muscle spasms usually in the calves, thighs, peri-scapular region

• Signs and symptoms of dehydration, thirst sweating, fatigue

• Treatment is stop activity, replace lost fluids with sodium containing fluids, gentle ice massage, stretching

• Recumbent position- more rapid distribution

• If prolonged recovery consider sickle cell trait or rhabdomyolysis

• RTP can be same day with rest and fluid replacement, some require 24 hr

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• Brief dizziness/fainting, tunnel vision, pale and sweaty, decrease pulse, normal rectal temperature

• Treatment

• Move to shaded areas, monitor vital signs, elevate legs and pelvis above head level, hydration (oral or IV)

• Resolves in less than 30 min

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Heat Syncope

Heat Exhaustion

• Excessive fatigue, fainting and collapses with minor cognitive changes (HA, dizziness, confusion)

• Can also have weakness, N/V, mildly hypotensive, elevated HR, (pre) syncope, vision changes, muscle cramps, hyperventilation, profuse (decrease) sweating, clammy skin/chills

• Should take rectal temp

– Can have mild- moderate elevation of rectal temperature of 100.4-104°F (38-40°C)

• At worst, heat exhaustion is difficult to distinguish form heat stroke

• Treatment

– Stop activity, Removal from hot environment, Cooling by removing clothing, ice water towels, ice packs, misting, cool hydration, Fluid replacement (oral or IVF)

– RTP: Usually 24-48 hours

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Case

• 55 year old man

• Finishing a ½ marathon

• Crossing finish line is staggering and appears confused

• Presents to medical tent

– Pale, clammy

– Not oriented to name or location or event/activity

• Wife is present

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Case

• EKG is done and normal

• BS is normal

• IV started with normal saline

• Rectal temp is 105.5

• Placed in CWI

– Becomes agitated and not cooperative

• Repeat rectal temp is 105

• EMS recommends to send to hospital

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Basic Principles

• 3 basic principals to assure favorable outcomes

– 1. Rapid assessment with rectal temperature

– 2. Immediate on site cooling until 102°F (38.8°C)

– 3. Use of cold water immersion for cooling

• 100% survival without major sequelae

– Cool 1st, Transport 2nd

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Exertional Heat Stroke

• Onset of severe neurologic dysfunction and rectal temp >104°F (40°C) differentiates from heat exhaustion

• Dizziness, vertigo, syncope

• Irrational behavior, confusion, irritability, emotional instability, hysteria, aggressiveness

• Delirium, seizures, coma or unconscious

• Most have hot sweaty skin

• Severe dehydration

• Flushed, hot, dry skin or hypotension, shock

• Mimickers

– Sickling, Hyponatremia, Hypoglycemia, Neurological conditions

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Exertional Heat Stroke

• Treatment

– TRUE MEDICAL EMERGENCY• May be fatal if not immediately diagnosed and properly

treated– Morbidity and mortality are directly related to intensity and

duration of hyperthermia

• Factors that determine successful treatment are– Anticipation, prompt recognition, rapid whole body cooling

– Delay in treatment can lead to rhabdomyolysis and acute renal failure

– Have an EAP/SOP17

• CAB’s and rectal temperature

• Rectal temperature is the gold standard for obtaining core body temperature

• Do not waste time substituting an invalid method of temperature assessment if rectal thermometry not available

• Rectal Thermometry

– Cover with lubricating

– (KY) or petroleum jelly

– Place SA prone or side lying (bend knees)

– Spread buttocks & gently

– Insert probe into rectum

– 15cm (6”)

– Use tape to secure in place

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On Field Treatment

• Rapid Cooling

– Aggressive cooling is the most critical factor

– Lower body core temperature as quickly as possible

• Immediately onsite

– Patient’s body should be immersed

• Removing clothing or pads/equipment can maximize surface area but can be time consuming

• Up to neck is most effective

• Water 35-59 F and continuously stirred

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On Field Treatment

On Field Treatment

• Equipment/Pad Removal

– Removal of pads and cooling rates and immersion duration were statistically different but unlikely to be clinically meaningful as the cool rates with and without pads were more than acceptable and pads do not prevent the body’s access to cold water

– Should remove pads if:

• Trained individuals are present to remove equipment from athlete with EHS

• The individuals treating the athlete with EHS are familiar with equipment removal

• The equipment is removed easily

• The necessary tools for uniform removal are available

• The athlete is compliant with medical personnel.

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• Continue treatment until rectal temperature decreases to 101-102°F (38.3-38.9°C)– Monitor rectal temp every 5-

10 min• Cooling rate ~ 1°F every 3

minutes

• Regain consciousness at ~ 102.2 °F/39°C

– Monitor vital signs

• Remove once at 102°F/38.9°C to prevent overcooling

• IF full body CWI not available do partial (torso)

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On Field Treatment

Treatment

• IF MD on site transportation to ER may not be necessary if cooling occurred immediately and pt is asymptomatic 1 hour later

• IF NO MD on site continue cooling until rectal temp 102°F/38.9°C

• Cool FIRST, Transport SECOND

– When medical staff not present coaching staff should cool until arrive

• Have an EAP/SOP

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Hospital Treatment

• Continue cooling until temperature normalizes– If immersion not feasible, then other methods

– Continue IVF rehydration

• Monitor for Multi Organ System Failure– For at least 24 hours

– Rhabdomyolysis , acute renal failure, shock liver

– Elevated liver enzymes and kidney function, metabolic acidosis

– Heart failure and arrhythmias

– Coagulopathy, anemia, low platelets

– Ventilate if respiratory failure

– Treat seizures and hypotension

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• EVERY MINUTE COUNTS!

• Morbidity associated with duration and magnitude of hyperthermia

• Overall mortality 15%

• If whole body cooling initiated within 10 minutes of collapse close to 100% recovery (Kark, et al 1996)

• First 30 min is Crucial for survival

• Poor outcome if DIC, temp >42.2°C, coma >4hrs

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Survival

Case Follow up

• In field temperature dropped to 98 when out of tub

• Was alert and cooperative

• Transported to ER

• Labs showed

– Normal CK

– Glucose 62

– BUN 17, Cr 1.18

– Electrolytes normal except low Ca at 8.4

– AST/ALT normal

– Normal UA

– Normal CBCPD

• Head CT was done given mild amnesia and negative

• Needed some blankets and warming given temp got down to 36.6°C/97.8°F

• Discharged home per pt preference after temp stabilized

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Case 2

• 15 year old cross country runner

• Collapsed and was confused and agitated

• Coaching staff dumped 3 coolers of cold water and packed iced packs in groin and axilla

• 911 called and transported to ER

– Rectal temp not taken

– Oral temp taken in the ER and “normal” (<100)

• Blood work showed elevated CK to 800’s, mild increase in Cr to 1.1, electrolytes normal

• Given IVF and discharged home for PCP to clear to return to play

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Heat Illness Return to Play

• No specific guidelines- ACSM Guidelines– Inability to accurately determine complete recovery– Refrain from exercise for at least 7 days following release from

medical care– Follow up in 1 week for PE and repeat lab testing/imaging– When cleared, begin exercise in cool environment and gradually

increase duration, intensity and heat exposure for 2 weeks to acclimatize and demonstrate heat tolerance

– If RTP difficult consider laboratory exercise heat tolerance test about 1 month post incident

– Clear athlete for full RTP if heat tolerance exists after 2-4 weeks of training

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Prevention- Education and Mandates

• Acclimatization- NATA position statement guidelines

• Gradually increase duration and intensity of activity over minimum of 7-14 days

• Earlier vasodilation and sweating

• Increase plasma blood volume

• Increase sweat rate and decrease fluid loss

• Lower core temp at given work load/heat stress

• After 1 week exposure to heat core body temp – 0.9°F (-0.5°C)

• 75% effect in the first 4 days

• Effect persists for 1-4 weeks

• If not maintained physiologic benefits dissolve within 3 weeks

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Prevention- Education and Mandates

• NCAA Requirements and MHSAA Requirements

– https://www.mhsaa.com/Schools/Health-Safety-Resources/Heat

• Acclimatization period

– Limiting practice duration and number per day

– Limiting equipment used

– Rest between 2 a day and time between 2 a day practices1 practice per day, limited to max of 3 hours

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• Risk increase substantially with multiple stressors

• PPE- prior EHI

• Sleep 6-8 hours

• Appropriate clothing

• Schedule to avoid hottest parts of day (10a-5p)

• Avoid direct sunlight

• Early morning or evening events

• Reschedule for dangerous conditions

• Allow acclimatization

• Buddy system

• Education of coaches, ATC, athletes

• Stop play for change in performance or symptoms

• Appropriate nutrition and hydration

• Match sweat and urine losses

• Avoid caffeine, alcohol

• Increase risk with certain medications

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Prevention- Education

• Appropriate medical care must be available

• Identify those particularly susceptible and closely monitor

– Illness

– History of or risk factors for EHI

• Conduct screening at PPE

– Physical condition

– Medications

• Anticipate potential problems– WBGT

– Heat Index

• Emergency supplies and equipment onsite– Cold water/ice tub available

– Rectal thermometer

• Emergency contact and health information

• Public Service Announcements

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Prevention- Planning

• Wet bulb globe– Measure of heat stress in direct

sunlight• accounts for humidity, wind

speed, temperature, sun angle , cloud cover

– Heat index: temperature and humidity

• Helps to risk stratify heat injury– Low, moderate, high, very high

risk

• EHS also can occur in relatively cool conditions

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Wet Bulb Globe

Wet Bulb Globe

• Events should not be scheduled if high humidity & temperature likely

• If WBGT >28 degrees Celsius, consider cancel

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Conclusion

• Why They Die: Errors In Care- Inaccurate temperature assessment/misdiagnosis

- No care/delayed treatment

- Inefficient cooling modalities

- Immediate transport (and/or waiting for transport)

- Rapid return to play

• Prevention and education is key

• Pre hydrate and replenish fluids apprpriately

• Continued research is necessary (and ongoing)!

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Conclusion

35Lento P, Sullivan W. The Downed Runner. Phys Med Rehabil Clin N Am 16 (2005) 831–849

Thank You

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References

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• Armstrong L, et al. ACSM Position stand: exertional heat illness during training and competition. Med & Exerc.2007;556-572.

• Casa DJ, DeMartini JK, Bergeron MF, et al. NATA Position statement: exertional heat illness. J Athletic Training. 2015;50(9):986-1000.

• Casa DJ, Guskiewicz K, Anderson S, et al. NATA position statement: preventing sudden deaths in sports. J Athletic Training. 2012:47(1);96-118.

• Casa Dj, Lawrence A, Kenny G, et al. Exertional heat stroke: new concepts regarding cause and care. Current Sports Medicine Reports. 2012;11(3):115-123.

• http://ksi.uconn.edu/

• Kucera k, Klossner D, Colgate B, Cantu R. Annual survey of football injury research 1931-2014. National Center for Catastrophic Sport Injury Research

• Lento P, Sullivan W. The downed runner. Phys Med Rehabil Clin N Am. 16 (2005) 831–849

• NCAA 2014-2015 Sports Medicine Handbook. Indianapolis, IN: NCAA.

• O’Connor FG, Casa DJ, Bergeron MF, et al. American College of Sports Medicine roundtable on exertional heat stroke – return to duty/return to play: conference proceedings. Curr Sports Med Rep. 2010;9(5):314–321.

• O’Connor F, et al. Practical management: a systematic approach to the evaluation of exercise related syncope in athletes. Clin J Sports Med. 2009;19(5):429-34.

• Smith JE. Cooling methods used in the treatment of exertional heat illness. Br J Sports Med.2005;39:503-7.

• Varghese GM, et al. Predictors of multi organ dysfunction in heatstroke. Br J Sports Med. 2005;22:185-7.

• Sawka M, et al. ACSM Position stand: Exercise and fluid replacement. Med & Exerc.2007;377-390.

• Wilder, R, O’Conner F, Magrum E (2014). Running Medicine. Montery, CA: Healthy Learning