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 • Individuals predisposed • Poorly conditioned • Sickle Trait? • Fatigue • Game vs Practice • Dehydration • 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 • Weakness • Elevated respiratory • Thirst rate • Nausea • Elevated pulse • Vomiting • Narrowed pulse • Dizziness pressure • Cramps • Headache • Sweating • Malaise • Mild Mental Status • Fatigue 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 • Illness control • Fitness • Medications • Conditioning • Education • Clothing • Environment risk assessment • Nutrition • Timing of event • Hydration • Monitoring of • Sleep conditions at event!