powerpoint presentation - heat-related illnessforms.acsm.org/tpc/pdfs/25 olson.pdf– exercise •...
TRANSCRIPT
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
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 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
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
• 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
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”
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
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