Heat-Related Illness David E. Olson, M.D. U of MN TPC 2013 Miami - - PowerPoint PPT Presentation

Heat-Related Illness

David E. Olson, M.D. U of MN TPC 2013 Miami

Agenda

• Physiology
• Predisposition
• Acclimatization
• Heat related illnesses
• Prevention

Physiology

• We are homeothermic

– Regulate or own warm-blooded body temp

• Maintain “normal” range

– 96.4 - 99.1 degrees F

Physiology

• Body’s ability to regulate core temp depends on

internal and external factors

• How heat is produced:

– Basal Metabolism

• Increases with increased core temp

– 10 percent elevation in BMR per 0.6 degree C rise

– Exercise

• Heat production 15-20x greater during exercise

– External Heat Sources

Physiology

• Hypothalamus is critical in heat physiology (the

thermoregulation center)

– Helps to control:

• Cutaneous blood flow (sympathetic)
• Sweat glands (parasympathetic)
• Cardiac output
• Stroke volume
• Usually efficient in a healthy individual

– 1 degree C change in core temp for every 25-30 degree C change in ambient temp

• Chronic Disease/Meds/Poor Conditioning are risks for

impaired control

Physiology

• How do athletes

control heat?

– Conduction – Convection – Radiation – Evaporation

• Work simultaneously

Conduction

• Occurs when the body comes in contact

with something cooler

• Heat is transferred to the cooler object

Convection

• When cool air passes over the skin
• Lifts heat away
• Windy days
• Fans

Radiation

• Heat released from

the body directly into the environment

Evaporation

• Sweat on the skin taking heat away from

the body

• **The primary thermoregulatory

mechanism when the ambient temp is above 20 degree C (68 degrees F)

• Need to be hydrated to maximize this!
• Incorporates processes of convection and

radiation

Physiology

• Assuming healthy athlete

– These 4 mechanisms are dependent on gradients of temp and moisture – As temp and humidity increase these are less efficient – Evaporation becomes the key in hot conditions!!

• Any process that limits this causes issues

– Dehydration – Clothing

Risk Factors Endogenous

• Acute Illness (fever, gastroenteritis)
• Chronic Illness (DM, CAD)
• Sleep deprivation
• Obesity
• Eating disorders
• Poor acclimatization
• Inexperience
• Motivation
• Dehydration

– 1% decrease in body weight can increase risk of heat illness

• Sickle Cell Trait
• History of Heat Illness
• Extremes of age (Elderly and Kiddos)

Risk Factors Exogenous

• Alcohol
• Stimulants
• Drugs of abuse
• Meds

– Anticholinergics, antihistamines, beta blocker, diuretics, neuroleptics, benzos, calcium channel blockers, tricyclic antidepressants and stimulants

• Environment

– Temperature, humidity

Children and Heat

• Special cases

– Produce more metabolic heat proportionately – Core temp rises faster when dehydrated – Smaller organ systems – Less efficient with heat dissipation

Acclimatization

• Physiological adaptation to hot, humid

environment

• 7-10 days
• Changes:

– Increase in blood volume (10-25%) – Increase in stroke volume – Decrease in resting HR – Sweat changes (earlier, more, dilute) – Skin vasodilates earlier

Heat Illness

• A spectrum of issues can occur
• Can occur anytime
• More likely in hot/humid weather
• Remember:

– Heat production is 15-20 greater with exercise!!!

• 240 deaths annually
• 3rd leading cause of death among US high

school athletes

Heat Illness Monitoring

• Patient monitoring

– Rectal temperatures – Pill monitoring devices

Heat Index Air Temp/Humidity

Heat Illness Monitoring

Major Risk in Heat Illness is high ambient temp with combined high level humidity

• Wet Bulb Globe Temperature

– Helps quantify the risk of heat injury

• Takes in to account

– Ambient temp – Radiant heat – Humidity

• WBGT=0.7WB + 0.2BG + 0.1DG

WBGT

• WB

– Thermometer with bulb covered with a wet cotton wick – Simulates the evaporation of sweat – Integrates effects of humidity, wind and rad

• BG

– 6 inch black globe – Radiation and wind

• DG

– Shielded thermometer from radiation – What is usually reported as the temp

Wet Bulb Globe Temperature

Different Classifications of WBGT: Military ACSM Green/Low 80-84 <65 Yellow/Medium 85-88 65-73 Red/High 88-90 73-82 Black/Very High >90 >82

WBGT Devices

Heat Illness Spectrum

• Heat Edema
• Heat Syncope
• Heat Cramps
• Heat Exhaustion
• Heat Stroke

Heat Edema

• Mild
• Transient peripheral

vasodilation

• Orthostatic pooling
• Mild dependent

edema on exam

Heat Syncope

• Syncope or pre-syncope caused by decrease in

vasomotor tone causing venous pooling

• Un-acclimatized or dehydrated athletes
• Usually at conclusion of exercise (worry if athlete

collapses prior to finish)

• Treated with rest, elevation of legs and fluids
• Can return to activity after resolution of

symptoms

Heat Cramps

• Localized, involuntary and sustained

contractions of skeletal muscle

• Causes:

– Sodium and/or chloride depletion – Dehydration

• Poorly conditioned athlete can lose more sodium along with

fluid than a conditioned athlete

– Impaired circulation in working muscles – Alterations in spinal neural reflex activity increased by fatigue

Heat Cramps

• Intensity dependent
• Poorly conditioned
• Fatigue
• Dehydration
• Individuals

predisposed

• Sickle Trait?
• Game vs Practice
• Supplement use

Heat Cramps: Treatment

• Stretching
• Massage/Ice
• Fluids

– Oral – IV

• Drugs

– Valium – Quinine

Heat Cramps

• Return to Play

– Rule out further Heat Illness – Resolution of symptoms – Correction of any underlying issues – Can be same day

Heat Exhaustion

• Most common form of Heat Illness
• Temp usually from 38 degrees C (100.4 F)

to 40 degrees C (104 F)

• Numerous symptoms or signs that happen

with exercise in warm humid conditions

• Can result from volume/sodium depletion

Heat Exhaustion Signs and symptoms

• Elevated temp
• Elevated respiratory

rate

• Elevated pulse
• Narrowed pulse

pressure

• Headache
• Malaise
• Fatigue
• Weakness
• Thirst
• Nausea
• Vomiting
• Dizziness
• Cramps
• Sweating
• Mild Mental Status

Alteration

Heat Exhaustion Evaluation/Treatment

• Obtain Core Temp!!!!!

– Rectal

• Rest

– Decrease heat production

• Shelter/Shade

– Remove from the hot environment – Minimize exposure to heat

• Cooling

– Fans/Ice tub/Towels

• Fluids

– PO usually in these case – IV

Heat Exhaustion Return to play

• Resolution of symptoms
• Normal Vitals
• Normal hydration status
• If in doubt……hold ‘em out

– Symptoms can return quickly and progress to Heat stroke!!

• Transfer if not improving or progressing to

heat stroke

Heat Stroke

• Life threatening clinical syndrome

characterized by loss of temperature regulation capabilities

• Second most common cause of death in

athletes in US

• Risk dependent upon:

– Endogenous heat production – Temperature/humidity – Individual predisposition

Heat Stroke Presentation

• Core temp now getting over 40 degrees C

(104 F)

• Similar presentation to Heat exhaustion
• Onset can be sudden

Heat Stroke Additional Signs/Symptoms

• Classic Triad

– Hyperpyrexia – Anhydrosis – Mental Status Changes

• Confusion
• Delerium
• Ataxia
• Seizures
• Coma

Heat Stroke Additional Signs/Symptoms

• Tachycardia
• Hypotension
• Arrhythmias
• Metabolic disturbance
• Clotting disturbances
• Rhabdo (Sickle Trait)
• Renal and Hepatic collapse

Heat Stroke Treatment

• REMOVE FROM HEAT!!
• Obtain Rectal Core Temp
• ABC’s
• Immediate cooling, if able, prior to

transport

• Then transport!!!

Heat Stoke

• With prompt recognition and treatment

survival rate is high (90-100 percent)

• The key is early recognition and treatment

(cooling)

Heat Stroke Cooling Methods

• Ice water immersion
• Ice water blankets

– Fans

• Ice packs
• Evaporative cooling

– Cool water/Warm air – .31 degrees C/min

How we roll in Minnesota

Heat Stroke

• Prognosis- dependent of length of time

and severity of hyperthermia

• Return to play

– May take some time – Normalize labs – Symptom resolution – Hydration status – Gradual

Exertional Hyponatremia

• Low sodium due to over-hydration in

prolonged exercise with dilute fluids

• Presents with: disorientation, pulmonary

edema, seizures, coma

• Rx- recognize and transfer
• Prevention- avoid over hydration with

dilute fluids during prolonged exercise

• More frequent seen with extreme

endurance events

Heat Illness Prevention

• Acclimatization
• Fitness
• Conditioning
• Clothing
• Nutrition
• Hydration
• Sleep
• Illness control
• Medications
• Education
• Environment risk

assessment

• Timing of event
• Monitoring of

conditions at event!

Heat Illness Case

• 25 yo AA football

player at his second day of training camp. Sickle Cell Trait positive.

• Long history of heat

cramps.

• Practice the first day

consisted of two 90 minute practices. Temp 83 degrees.

• Mild cramps after first

practice of second day

• Down 8 pounds
• Pushing PO fluids
• Resolves
• Eats
• 4 hour break inside air

conditioning

• Checks in before second

practice

• Feels “good”

Case

• Returns to afternoon

practice in 85 degree heat.

• Cramps return

– Full body

Treatment

• IV fluids
• Not improving
• Sent to Hospital
• CK max to 120k
• Inpatient for 2 days
• Return to play issues!

– Follow CK to normal? – Symptoms? – Gradual increase activity

What could have helped prevent issues??

• More time to

acclimatize

• Shorter practice time
• Early/later practice
• Better hydration
• Hold out after first

practice

• Better training prior to

camp

Should there be special considerations for sickle trait patients??

• NCAA

Testing/Protocols

• Mandatory testing

unless waiver is signed

• Started April 2010

Summary

• Understanding basic physiology of heat transfer

and balance provides the framework for understanding heat illness and treatment

• Identify who may be predisposed to problems
• Have a plan for monitoring the heat
• Heat illness can be life threatening; early

diagnosis and treatment can be life saving

Thank You!!

Resources

• Bently S. Exercise induced muscle cramp. Sports Med 1996 Jun:21 (6); p 409-420
• Miners. The diagnosis and emergency care of heat related illness. The Journal of the

Canadian Chiropracitc Association, June 2010.

• Carter R, et al. Epidemiology of hospitalizations and deaths from heat illness in
• soldiers. Med Sci Sports Ex 37(8), August 2005, pp 1338-1334.
• Coris EE et al. Heat illness in athletes. The dangerous combination of heat, humidity

and exercise. Sports Med 2004; 34(1) p 9-16.

• Eichner ER. Treatment of suspected heat illness. Int J Sports Med 19: S150-153.
• Maughan RJ. Exercise in the heat; limitations to performance and the impact of fluid

replacement strategies. Can J Appl Physiol 24(2): 149-151, 1999

• Seto CK, et al. Environmental illness in athletes. Clin Sports Med 21 (2005) p695-718
• Wexler Randall, Evaluation and Treatment of Heat Illness, American Family
• Physician. June 1, 2002