Preventing & Caring for Exertional Heat Stroke

Essential Emergency Equipment

• Automated External Defibrillator (AED)

• Glucometer

• Rectal thermometer

• 150 gallon tub for cold water immersion

• Unlimited supply of ice and water

• Easy up tent

• Cell phone

• Expendable first aid supplies

• Documented and rehearsed emergency action plan

• Wet bulb globe temperature (WGBT) device

Prevention: Prescreen Athletes to assess for history of heat illness of presence of risk factors of heat illness

Level of evidence: C

• History of EHI

• Inadequate heat acclimatization

• Low fitness level

• Overweight or obese

• Inadequate hydration

• Poor sleep hygiene

• Fever

• Stomach illness

• Highly motivated / ultra-competitive

• Pre-pubescent

Prevention: #2

Strength of Recommendation: B

Allow athletes to acclimate to the heat over the course of 7-14 days by gradually increasing intensity and duration of exercise

Day 1-5: no more than 1 practice per day, no more than 3 hours per day (total), 1 hour max walk through is allowed but then need 3 hour recovery period before practice

Days 1-2 Equipment: helmet only

Days 3-5 Equipment: helmet and shoulder pads -> contact with blocking sleds and dummies

Day 6 Equipment: ALL equipment allowed -> 100% live contact

Days 6-14: double day practices are allowed, followed by a single practice day, 2 practices -> rest day -> 2 practices, 2 practice -> can’t exceed 3 hours (in one practice, cant exceed 5 hours total), 3 hour recovery in cool environment between

Prevention: #3

Strength of Recommendation: B

Ensure fluids are available and easily accessible before, during, and after practice. Encourage Rehydration

Prevention: Proper hydration

Begin hydrated:

• 2-3 hrs prior to activity 17-20 fl oz

• 20 min prior 7-10 fl oz

• 40 min to restore plasma volume/electrolytes

During Activity

• 7-10 0z every 10-12 minutes

Prevention: Post activity rehydration

Rehydration should occur within 2 hrs post exercise to assure optimal rehydration. Post exercise rehydration should be 150% of body mass loss during exercise.

Pre exercise wt (kg) - post exercise wt (kg) x 1.5 = Fluid needs for replacement per ACSM guidelines

For every 1 kg (2.2 lb) loss, additional 1 L of fluid needed

Fluid Replacement After Exercise
BM loss	Fluid Needed
0.5 kg (1.1 lbs)	0.5 L
1 kg (2.2 lbs)	1 L
1.5 kg (3.3 lbs)	1.5 L
2 kg (4.4 lbs)	2 L
2.5 kg (5.5 lbs)	2.5 L
3 kg (6.6lbs)	3 L

Prevention: Clinical hydration measurments

• Urine specific gravity - ration between density of urine and density of water

  • Euhydration < or equal to 1.020

  • Dehydration > or equal to 1.020

• Measurement

  • Urine reagent strip - cheap, not as sensitive in hypo-hydrated state

  • Refractometer - preferred

Clinical Hydration measurements (Body Mass & Urine color)

• Body mass

  • 50-70% of body is water

  • May lose 5% in one session

  • Pre/post exercise

• Urine Color

  • Normal: light yellow

  • Severe: brownish green

Activity Modification (Prevention: #4)

Adjust practice times, sessions, and equipment according to environmental conditions and fitness level

Strength of recommendation: C

WBGT Index

WBGT (overview)

• Utilizes ambient temperature, relative humidity, wind, and solar radiation from the sun to get a composite value that can be used when monitoring environmental conditions during exercise in the heat.

WGBT = 0.7T_W+0.2T_G+0.1T_D

T_w is the wet bulb temperature, which indicates humidity

T_G is the globe temperature, which indicated radiant heat

T_D is the ambient air (dry) temperature

Nutrition

• Electrolyte consumption

• Lightly salty food

• Watery foods - fruits

• Avoid caffeine & alcohol

Sleep guidelines

• Encourage 6-8 hrs of sleep each night in a cool environment

• Sleep deprivation has negative impact on acclimation to heat

Recognition Heat Stroke : Types

1. Classic

   • Under heat wave conditions/illness of unfit-sick

2. Exertional

   • illness of young and fit

   • Severe hyperpyrexia (>104 degrees F)

     • 1 F = 7% metabolic increase

Recognition HS: Key Points

• Core body temperature >104-105 degrees F

  • Measured via rectal probe or gastrointestinal temp immediately following collapse

  (Strength of recommendation: B)

• CNS dysfunction

  • Mental status change

  • Dizziness

  • Collapse

  • Irritability

  • Irrational Behavior

  • Confusion

(Strength of recommendation: B)

Recognition HS : S/SX

• Disorientation

• Staggering

• Seizures

• LOC - most will have lucid interval first

• Coma

• Hot, dry or wet skin

• Dehydration

• Tachycardia (100-120 bpm)

• Hypotension

• Hyperventilation (shallow & rapid)

• Vomiting

• Diarrhea

ALL emergency assessments begin the same

Measuring Core Body Temperature

• Rectal temperature is the GOLD standard

• Other measurements are shown to be inaccurate and unreliable in heat stress patients

• Oral gets worse as a predictor as they get hotter

  • No correlation between rectal temp and oral temp, axillary temp, tympanic temp or temporal temp

  • No correction factor

Rectal Temp

• Assessing rectal temperature

  • flexible thermistor

  • Inserted 10 cm past anal sphincter (lift up buttocks)

    • Put tape at 12 cm mark to hold on to

• Danger zone - 105 degrees >

• 5-7 minute window within 30 minutes of collapse to get patient below 105 degrees F

  • Athlete should be cooled to 102 degrees within first 30 minutes after collapse

Taking a Rectal Temperature

1.Place patient in a side-lying position with top knee bent

2.Place towel over hips

3.Wash/sanitize hands, don gloves

4.Lower pants/underwear to below the gluteal fold

5.Prepare the thermometer (have correct thermometer, clean instrument with alcohol)

6.Apply thermometer sleeve and lubricant

7.Lift top buttock to visualize rectum

8.Insert thermometer into the rectum 1.5 inches (3.5 cm)

9.If using a thermistor thermometer, insert flexible probe 4-6 inches (10-15 cm) past the anal sphincter into the rectum

10. Wait for digital reading

11. Remove the thermometer; dispose of the sleeve; clean the thermometer with alcohol

12. If using a thermistor thermometer, the measuring aspect may remain in the patient’s rectum until cooling temperature of 102°F has been reached

Why do people die? HS

• No care: no AT present

• Inappropriate care: failure to assess core temperature accurately and therefore make wrong treatment decision

• Inadequate cooling methods: cold water immersion is gold standard

• Ambulance delay: COOL first, TRANSPORT second

Complications due to delayed treatment of EHS

Survival without complications

• cooling 0-30 min following collapse

Long term complications

• 30+ min following collapse

Permanent complications

Death

Treatment: key points

1.Cold-water immersion until core body temperature is ≤102°F

–Strength of recommendation A

2.Monitor other vitals

–Strength of recommendation B

3.After body temperature is ≤102°F transport to the hospital and monitor blood work for elevated enzyme levels

–Strength of recommendation B

4.Return to play should involve a gradual introduction and consequent combination of exercise, heat, and protective equipment under the supervision of a medical professional (pending normal blood work and physician clearance).

–Strength of recommendation C

Cooling methods for EHS

• Aggressive cooling in cold water immersion bath within 10 minutes of collapse

  • takes 90 minutes to cool with peripheral methods

• Water temp should be around 40F

• stir water w/ paddle to avoid developing a thermopane

• Use sheet under arms to support patient in case LOC

• Keep flexible thermistor inserted during bath to monitor temp

• Remove when reach 102F

  Cold saline IV is second best tool but not available until in ER

Cooling Rates

• Cool 4x faster in water than in air

• Decrease 1F every 3 minutes average over 12 minutes

• Cooling during 1st 6 min is slower than faster in next 6 mins

• Normal thermic patient will increase temp during first 20 mins

  • EHS patient will decrease temp

• Normal thermic patient will shiver and have vasoconstriction

  • EHS patient - hypothalamus overrides and causes little vasoconstriction and no shivering documented

  • Cardiovascular shock only a concern in delayed care situations or passive heat stroke in the elderly

IF no rectal thermometer

•Have a documented emergency action plan

•Know the KEY signs/symptoms

–Elevated core temperature

–CNS changes

•Remove from the heat

•Remove equipment and sweaty clothing

•Cool down entire body

–Iced towels rotated every 3-5 minutes

–Cold water immersion 15 minutes

• Take caution as patient will likely lose consciousness

• Call EMS

-Be aware that EMS is not currently trained in assessing rectal temperature nor do that have rapid cooling methods

Comparison of common non-trauma causes of on-filed collapse

SCT Sickling	Cardiac	Heat Stroke
Weakness > pain	No cramping	Fuzzy thinking
Slumps to ground	Falls suddenly	Bizarre behavior
Can talk at first	Unconscious	Incoherent
Muscles “normal”	Limp or seizing	Can become unconscious
Temp < 103	Temp irrelevant	Temp >104
Can occur early	No warning	Usually occurs late

Return to Play

• Asymptomatic

• Achieve and maintain full hydration

• Physician clearance

  • normal lab tests

• Resolution of any underlying conditions

  • ID predisposing factors

• Gradual return = re-acclimatization

Thermoregulation 101

• Core Body temp

S = M ± R ±  K ± Cv – E

S = amount of stored heat

M = metabolic heat production

R = heat gained or lost by radiation

K = heat gained or lost by conduction

Cv = heat gained or lost by convection

E = heat gained or lost by evaporation

Thermoregulation: definitions

Radiation – energy is transferred to or from an object or body via electromagnetic radiation from higher to lower energy surfaces (we absorb radiant heat from the sun)

Conduction – heat transfers from warmer to cooler objects through direct physical contact (ice bags)

Convection – heat transfers to or from the body to surrounding moving fluid or air (moving air from a fan, wind, moving water)

Evaporation – heat transfers via the vaporization of sweat and is the most efficient means of heat loss

Sweating

• Begins 1-2 sec. after exercise begins

• Reaches equilibrium in direct relation to exercise load in 30 mins

• Adult sweat output of 1 - 2 liters / hour

• Peak of 3 liters / hour

• 2-3% loss of body weight impairs function

Inter-Association Task Force for Preseason Secondary School Athletics Participants

• Initial 14 consecutive days of preseason practice

• 1 day of complete rest every 6 days

•Need for heat exposure every 4 days

•Smaller rise in core temperature a result of:

–increased stroke volume   

–extracellular fluid volume expansion

–diminished sweat [Na⁺]

–increased sweat volume

Heat Syncope

• Typically occurs first 5 days of acclimatization before blood volume expands

• Dehydration

• Peripheral vasodilation

• Postural pooling of blood

• Dizziness

• Lightheadedness

• Fainting

• Fatigue

• Tunnel vision

• Pale or sweaty skin

• Decreased pulse rate

• normal core body temp <104 F

• TX: elevate feet in supine, rehydrate

Heat Exhaustion

• Caused by inadequate CV response to circulatory stresses caused by heat

• Slow, progressive, Peripheral vascular collapse  

• Predisposing Factors   

  • young, old, hypertensive

• Heavy sweating, vomiting, dehydration, sodium loss, energy depletion

Those at risk : Heat Exhaustion

•Exercising in hot and humid environment (air temp > 33°C, 91.4F)

•Inadequate fluid intake before or during exercise resulting in dehydration

•Inappropriate work to rest ratios with too much work compared to rest breaks

•Body mass index > 27 kg/m

Heat Exhaustion S/SX

•Headache, fatigue

•Dizziness, nausea

•profuse sweating

•Pale, cool, clammy skin

•Rapid, weak pulse

•Rapid shallow respirations

•BP decreased

•Temperature 97-103.9F

•Dehydration

•Lightheadedness

•Syncope

•Anorexia

•Diarrhea, intestinal cramps, urge to defecate

•Decreased urine output

•Persistent cramps

•Chills

Heat Exhaustion : Treatment

•Treatment

–move to cool environment

•Inside, shade, fans, AC

–if temp elevated apply cool towels or sponge

•Keep cooler of towels in ice bath on the field

•Remove wet clothing, helmets/hats, socks, shoes

–monitor vital signs

–give cool fluids if conscious and alert 

–Will get better in 5-10 minutes

–No RTP for at least 24 hours

(Gradually increase intensity and volume of exercise)

Hyponatremia

• Core body temp <104F

• Excessive water consumption and/or decreased Na+ intake

• Serum Na+ < 130 mmol/l

• Activity > 4 hrs, rare….

Signs and Symptoms

•. Disoriented, progressive headache, nausea, vomiting, swelling of extremities

• Leading  to Cerebral edema, pulmonary edema, death

Prevention

•. Fluid intake with Na+

Sickle Cell trait

Sickle cell trait is the inheritance of one gene for sickle hemoglobin Hb S and one for normal hemoglobin Hb A. During intense or extensive exertion, the sickle hemoglobin can change the shape of red cells from round to quarter-moon, or “sickle.” This change, exertional sickling, can pose a grave risk for some athletes. In the past seven years, exertional sickling has killed nine athletes, ages 12 through 19.

5 major concerns for athletes with SCT

•Genetic counseling

•Splenic infarction at altitude

•Bleeding in the urine

•Inability to concentrate urine

•Exertional rhabdomyolsis

What happens SCT

• Sickle cells can accumulate in the bloodstream during intense exercise

• Ischemic rhabdomyolysis

– Rapid breakdown of muscles starved of blood

– Blood vessels collapse due to “log jam” of sickled cells

Sickle Cell trait & Exercise : Overview

• Each cell has ~ 40% Hgb S and ~ 60% normal Hgb A

• Strenuous exertion causes sickling of some cells because of:

  • Hypoxemia

  • Hyperthermia (due to increased muscle heat)

  • Metabolic acidosis

  • Dehydration of red cells (increases concentration of Hgb S)

• Sickle cells log jam and stop blood supply

  Ischemic rapid muscle breakdown = explosive rhabdomyolsis

Sickle Cell trait & exercise: definitions

• Acute Ischemic rhabdomyolysis: the rapid breakdown of muscle tissue starved of blood

• Acute Rhabdomyolysis: a serious and potentially fatal condition involving the breakdown of skeletal muscle fibers resulting in the release of muscle fiber contents into the circulation

• Exertional rhabdomyolysis: muscle breakdown triggered by physical activity

• Exertional sickling: hemoglobin [red blood cell] sickling due to intense or sustained physical exertion

• Hyperthermia: body temperature elevated above the normal range

• Hypoxemia: decreased oxygen content of arterial blood

• Ischemia: a deficiency of blood flow to tissue

• Metabolic acidosis: a condition in which the pH of the blood is too acidic because of the production of certain types of acids

Sickling Collapse

•Typical events leading to a collapse:

– High altitude running

– Sprints or “gassers” that occur early in practice

•Think of the typical practice…”work hard and then kill ‘em at the end.”

– Sickling can occur as quickly as during 2-3 minutes of sprinting

– Typically occurs early in season or during preseason

– Can quickly increase to grave levels

– The harder and faster the athlete runs the earlier and greater the sickling occurs

– Increased likelihood in the heat…why?

Telltale sigs: Heat cramps vs Sickling

•Heat Cramps

– Muscle twinges

– Excruciating pain with cramps

– LOF is different – hobble to a halt with “locked up” muscles

– Writhe and yell in pain with rock hard muscles

•Sickling

– None

– Not as painful

– LOF – slumps to the ground with overall muscle weakness

– Lie fairly still with muscles that look and feel normal

Recommendations for Sickle cell trait Athletes

• Should not be disqualified – modifications and precautions should be in place

– Build up slowly in training progression, longer rest/recovery periods

– Participate in preseason strength and conditioning but exclude from mile runs, serial sprints, etc.

– Cessation of activity with onset of symptoms

– Year-round periodization strength and conditioning program that is athlete/sport specific

– Must have adequate rest/recovery if participating in high speed sprints and/or interval training

• Ambient heat stress, dehydration, asthma, illness, and altitude predispose the athlete with sickle trait to an onset of crisis in physical exertion.

– Adjust work/rest cycles for environmental heat stress

– Emphasize hydration

– Control asthma

– No workout if an athlete with sickle trait is ill

– Watch closely the athlete with sickle cell trait who is new to altitude. Modify training and have supplemental oxygen available for competitions

Sickle Collapse - MEDICAL EMERGENCY

1.Check vital signs.

2.Administer high-flow oxygen, 15 lpm (if available), with a non-rebreather face mask.

3.Cool the athlete, if necessary.

4.If the athlete is obtunded or as vital signs decline, call 911, attach an AED, start an IV, and get the athlete to the hospital fast.

5.Tell the doctors to expect explosive rhabdomyolysis and grave metabolic complications.

6.Proactively prepare by having an Emergency Action Plan and appropriate emergency equipment for all practices and competitions.

Acute Exertional Rhabdomylosis

• Sudden catabolic destruction and degeneration of skeletal muscle (myoglobin and enzyme leakage into vascular system)

• Occurs during intense exercise in heat and humidity resulting in:

– gradual muscle weakness, swelling, pain, dark urine, renal dysfunction

– severe case = sudden collapse, renal failure and death

• Associated with individuals that have sickle cell trait

• Emergent Referral