Some Like It Hot!

2016 BRONSON SPORTS MEDICINE SYMPOSIUM: RETURN TO PLAY

July 29, 2016

Stacy Majoras, DO, ATC Bronson Sports Medicine Specialists Disclosures Disclosures

• I, nor my family, have any financial or other disclosures to share

Objectives

• Review and establish heat precautions • Review heat related illness • Discuss management of heat illness • Discuss return to play options following heat illness • Consider special populations

Thermoregulation

• The Players of Thermoregulation – Hypothalamus – great regulator • Monitor blood flow to brain AND thermoreceptors  increased heat production or heat loss to bring the body temperature back to the “set-point” • Regulated core body temperature varies ~ 1°C (circadian rhythm, menstrual cycle, distribution) – Skin • Heat  cutaneous vasodilation – Cutaneous vasodilation can increase cardiac output 60% • Exercise  cutaneous vasoconstriction – Eccrine Glands (Sweating) • Sympathetic (fight) cholinergic nerve fibers • Electrolyte composition – Sodium > Calcium / Magnesium – Modified by reabsorption of sodium in sweat duct  hypotonic compared to plasma – Sweat sodium concentration varies by diet, sweat rate, and degree of acclimatization • Sweat Rate is typically between 1.0-2.5L/hr (>2.5L if high temperature) Thermoregulation

• Appropriate response to heat – Increase in core body temperature  activate peripheral and hypothalamic heat receptors  • Increase in cardiac output (increased distribution to skin) • Vasodilate skin blood vessels • Stimulate sweat gland secretion (when body temperature cannot be regulated by sensible heat loss, sweating is initiated and closely parallels body temperature (maximum sweat rates ~ 39°C)) • No heat lost from body with T 97o & > 90% humidity (well into the red) Thermoregulation

• Adverse Response to Heat = Thermoregulatory Failure – Lactic Acidosis • Lactic acidosis due to energy depletion  stimulation of ATP- dependent Na+-K+ pump  ATP depletion / failure of ion- transport  accumulation of Ca++ (+ lactic acid)  cell hypoxia and necrosis – Dehydration can attenuate heat transfer and heighten cardiovascular collapse • Hypohydration  increased core temp / heart rate at rest and exercise AND reduction of sweat rate (above 5% reduction in body weight) – Classical Symptom • Cease sweating in heat stroke (rare in clinical)

Objectives

Heat Precautions

First step in prevention is identifying those at risk

– Intrinsic Factors • Age > 40 y/o • H/o exertional heat stroke • Inadequate acclimatization or conditioning • Low fitness level • Overweight • Fever and/or Illness • Competitive • Pre-pubescent • Medications (anticholinergics, antihistamines, stimulants, ACE-inhibitors, diuretics) • Skin disease • Chronic medical illness • Sickle cell Heat Precautions

First step in prevention is identifying those at risk

• Extrinsic Factors – Exercise with minimal breaks – High temperature, humidity, sun (increased WBGT) – Clothing – Equipment – Lack of education – Limited fluid access – Baseline dehydration – Medications (anticholinergics, antihistamines, stimulants, ACE-inhibitors, diuretics) – Inadequate hydration – Dietary supplements

Heat Precautions

Heat And Hydration l July 28, 2016 l 11 Heat Precautions WBGT

Heat And Hydration l July 28, 2016 l 12 Heat Precautions WBGT

Examples

Wind HeatIdx Temp F Dwpt F RH % Sky % WBGT F mph F

90 65 42 05 03 92 89 WBGT=.7T90 65 w+.2T42 g+.1T05d 13 92 83

90 65 42 65 13 92 81 Tw is the wet bulb temperature, which indicates 90 70 52 10 06 96 88 humidity 90 70 52 60 06 96 86 Tg is the globe temperature, which indicates radiant90 heat70 52 60 13 96 85 100 70 39 10 13 108 90 Td is the ambient air (dry) temperature 100 70 39 10 5 108 94 100 70 39 65 05 108 91 Heat Precautions

• Most effective prevention = heat acclimatization and rehydration – Heat Acclimatization • Decreased core temperature at rest • Decreased HR during exercise • Increased sweat rate (and sensitivity by decreasing “set- point” for sweating and cutaneous vasodilation) • Decreased Na loss in sweat (increased reabsorption) / urine • Increased plasma volume – Heat Acclimatization Recommendations • Begins in a few days, full adaptation by 7-14 days • Different organ systems adapt at varying rates • > 50% VO2 max x 100 minutes to maintain elevated core temperature and sweat rate critical for optimal heat acclimatization • Lost in same pattern as gained

Heat Precautions NCAA / High School Acclimatization Recommendations

Heat And Hydration l July 28, 2016 l 15 Heat Precautions

• Rehydration – Heat acclimatization  increases fluid replacement due to earlier onset of sweating – Advantages of heat acclimatization are abolished with dehydration – Choice beverage to rehydrate • Gastric Emptying : increased volume (increased energy content)  increased gastric emptying • Intestinal Absorption: glucose (~ 6-7% carbohydrate) + sodium increase water absorption in small intestine due to more favorable fluid gradient • Fluid Retention in ICF/ECF compartments … Urine output inversely proportional to sodium content (Maughan et al.) Heat Precautions

• Rehydration Recommendations – If sweat rate is known (next slide) • Individualized replacement based on sweat rate – If sweat rate is not known • 200 - 300 mL (7-10 oz) every 10-20 minutes for events > 30 minutes – 2% body mass loss is acceptable – 6-7% carbohydrate drink is optimal (>7%  delayed gastric emptying and decreased intestinal absorption) – Multiple carbohydrate forms  greater absorption due to solute transport mechanisms – Increased Na content in beverage  increased Na in sweat … thus water + salty food may be more advisable than increased Na content in beverage • Water goes where the salt is

Heat And Hydration l July 28, 2016 l 17 Heat Precautions Objectives

Heat Illness

• Caused by overexertion in high temperatures and high humidity • 2 categories of heat illness – Illness without increase in core temperature – Illness with increase in core temperature Heat Illness

• 2 categories of heat illness – Illness without increase in core temperature • Heat rash • Heat cramps • Heat tetany – Illness with increase in core temperature • Heat Exhaustion – normal behavior • Heat Stroke – abnormal behavior • Core temperature over 102 needs to be cooled • For every 5 min of vigorous exercise the body increases 1C

Heat Rash

• Definition • Treatment – Erythematous rash associated with – Cooling exercise or increased skin temperature – Showering • Mechanism – Topical steroids if – Proposed “causes” include: severe • Blocked sweat glands • Return To Play • Release of histamine with exercise – Per athlete as • Predisposing factors tolerated – Clothing • Prevention – Tropical climates – Wear appropriate • Signs and symptoms clothing – Raised, papules with erythematous base – Pruritic Heat Cramps

• Definition – Painful cramping in legs , arms, abdominals with muscle contractions • Mechanism – Unknown, proposed “causes” include: • Poor hydration • Lack of adequate salt • Predisposing factors – Exercise-induced muscle fatigue – Excessive body water loss – Excessive sodium loss – Personal history – Increased running speed – Previous muscle or tendon injury • Signs and symptoms – Dehydration – Thirst – Sweating – Muscle cramps – Fatigue – Twitches aka: fasciculation Heat Cramps

Heat Cramps

• Treatment – Decreased activity and oral rehydration – Massage with muscle in full- length position • Return To Play – Per athlete as tolerated • Prevention – Maintain fluid / salt balance – Supplemental sodium Heat Tetany

• Definition • Treatment – Muscle contraction without – Rehydrate relaxation – Do not try to stretch muscle – Severe cramp – Muscle relaxer – if severe may • Mechanism require injection – Dehydration of muscle with • Return To Play progressive work ending in failure – When full strength and ROM of • Predisposing factors limb is regained – Continuing to exercise despite • Prevention cramping – Treat muscle cramping when it • Signs and symptoms starts – Cramping of muscle off and on – Consider extensive pre – exercise hydration schedule Heat Illness

Heat Illness

• Heat exhaustion – Syndrome of hyperthermia (core temperature at time of event usually <40°C or <104°F) with physical collapse or debilitation occurring during or immediately following exertion in the heat, with no more than minor central nervous system (CNS) dysfunction (e.g., headache, dizziness). HE resolves rapidly with minimal cooling intervention • Heat injury – HE with clinical evidence of organ and/or muscle (e.g., rhabdomyolysis) damage without sufficient neurological symptoms to be diagnosed as heat stroke • Heat stroke – Syndrome of hyperthermia (core temperature at time of event >40°C or 104°F), physical collapse or debilitation, and encephalopathy as evidenced by delirium, stupor, or coma, occurring during or immediately following exertion or significant heat exposure. Can b complicated by organ and/or tissue damage, systemic inflammatory activation, and disseminated intravascular coagulation. Heat Exhaustion Exercise-Associated Collapse (EAC)

• Definition – Most common heat-related illness – “Inability to continue exercise in the heat due to cardiovascular insufficiency and energy depletion” vs “syncopal-like” event • Mechanism – Cardiovascular insufficiency = inability of heart to provide oxygenated blood to peripheral musculature vs autonomic “dysfunction” – Orthostasis Heat Exhaustion Exercise-Associated Collapse (EAC)

Heat Exhaustion Exercise-Associated Collapse (EAC)

• Predisposing factors • Signs and symptoms – Exercising in hot / humid – Increased core temp (36-40°C, environment 96.8-104°F) – Inadequate fluid intake – Hypotension – Inappropriate work to rest ratio – Bradycardia – BMI > 27 kg/m2 – Hyperventilation – No heat lost from body with T 97o & – Excessive sweating > 90% humidity (well into the red) – Dizziness – Lightheadedness – Loss of consciousness – Diaphoretic – clammy, pale – Weakness – Tunnel vision – Fatigue – Headache – Decreased muscle coordination – Nausea and/or vomiting – Chills – Decreased urine output – Irritability Signs of Dehydration

• Percent body weight lost – 1% – Thirst – 2% – Start to thermoregulate – 3% – Dry mouth – 4% -- Decrease in physical work – 5% -- Difficulty concentrating, HA, lethargy – 6% -- Impaired thermoregulation – 7% -- Collapse Heat Exhaustion Exercise-Associated Collapse (EAC)

• Treatment – Cool / shaded area – Remove clothing – Elevate legs  increase venous return – Cool with fans, ice towels, ice bags – Rehydrate (oral fluids)  expand plasma volume – Recover within 10-15 minutes with minimal treatment and monitoring …. or consider heat stroke • Return To Play – Same day return to play not advised – Rehydration and re-acclimatization Cooling

• Radiation – Transfer of energy through infrared waves • Conduction – Transfer of heat through direct contact with solid, liquid or gas – Cold towels, wind, cold tubs • Convection – Conduction of heat to surrounding air – Fans • Evaporation – Transformation of liquid to gas – Sweating • Respiration – Loss of heat and moisture through breathing Replacing

• Pre and post exercise weight checks • Thirst is the best indicator especially for kids • When to drink – 1-2 hours before exercise 16 – 20 oz – Every 10-20 minutes of exercise 7-10 oz. – After exercise 16 oz. of fluids for every pound lost • What to drink ???? – Water – Chocolate milk – Sports drinks Exertional Heat Stroke

• Definition – CNS dysfunction + hyperthermia • Irritability, emotional instability, altered consciousness, collapse, coma, dizziness + rectal temperature > 104°F • Mechanism – Reduced Central Venous Pressure – Splanchnic ischemia – Lactic acidosis •  increased core temperature + circulatory failure + lactic acidosis  renal dysfunction/failure, liver dysfunction/failure, and coagulopathy Exertional Heat Stroke

• Signs and symptoms – Progressive decline of consciousness followed by unresponsive – Lack of response to treatment of EAC • Complications – Severe encephalopathy (most concentrated in the cerebellum) – Acute renal failure (recovery takes weeks) – Acute respiratory distress syndrome – Myocardial injury (recovery takes hours) – Intestinal ischemia – Pancreatic injury – Disseminated intravascular coagulation – Rhabdomyolysis (biomarkers elevated for 1-4 days) – Hepatocellular injury (biomarker recovery takes 1-2 days, hepatic tissue injury takes weeks to months) Exertional Heat Stroke

• Treatment – Early recognition and rapid cooling – Rapid cooling by ANY method available reduces morbidity and mortality • Remove equipment and clothing and initiate whole body cold-water immersion with the water aggressively stirred to induce the fastest cooling rates • Or rapidly rotating ice water-soaked towels or continuously spraying with cold water can be nearly as effective – Monitor vital signs • ONLY use RECTAL thermometer • Stop when rectal temperature is < 102°F (38.9°C) – 100% Survival rate when immediate cooling was initiated within 10 minutes • Prognosis – Worse when core temperature remains > 40°C for any period of time (~ 30-60 minutes) and early intervention is delayed Take the Temperature!!! Exertional Heat Stroke

• Return To Play – ACSM’s position statement • The currently available science cannot support a high-level, evidence-based, consensus return-to-play document, and much work has yet to be accomplished – ACSM’s Guidelines (2010) • Refrain from exercise for at least 7 days following release from medical care • Follow up 1 week post incident for physical examination and lab testing or diagnostic imaging of affected organs based upon the clinical course of the heat stroke incident • When cleared for return-to-activity, begin exercise in a cool environment and gradually increase the duration, intensity, and heat exposure over 2 weeks to demonstrate heat tolerance and to initiate acclimatization • If return to vigorous activity is not accomplished over 4 week, consider a laboratory exercise-heat tolerance test • Clear the athlete for full competition if heat tolerant after 2 – 4 week of full training

Objectives

Special Populations Exertional Sickling

• Definition • Treatment – Sickle Cell Trait (8% in African- – Stop activity, American people and 0.05% in – Check vital signs Caucasian people) – High flow oxygen – RBC morphologic change (15L/min), (sickle)  build up of RBCs in blood vessels  decreased – Alert hospital staff (rhabdo) blood flow  rhabdomyolysis then transfer • Signs and symptoms • Prevention – Cramping – Screen – Muscle weakness > muscle pain – Modify participation as – “slumps” > collapse necessary – Able to speak – Otherwise similar to heat – – Muscles look and feel normal related illnesses – Rapid breathing with adequate • Return To Play air movement – Similar to heat – related – Rectal temperature < 103°F illnesses Special Populations

• Paraplegic/spinal cord injury athletes – Changes in autonomic regulation systems including how they tolerate heat and dehydration – They may not experience warning signs until it is too late – Monitor vital signs – Wheelchair bound athletes may have increased blood pressure due to urine retention and obscure initial evaluation • Senior athletes – Slower response to heat • Pediatric athletes – Discussed earlier Pearls to leave you with …

• Children, senior, and special needs athletes are at greatest risk of heat illness • Cool first ask questions later • If they are that hot they will not mind the rectal thermometer • If they do not cool fast transport fast

References

• Epstein Y, Roberts WO. The pathophysiology of heat stroke: an integrative view of the final common pathway. Scand J Med Sci Sports. 2011: 21: 742–748 • Wendt et al. Thermoregulation during exercise in the heat. Sports Med. 2007;37(8);669- 682. • O’Connor et al. American college of sports medicine roundtable on exertional heat stroke and return to duty/return to play: conference proceedings. Curr. Sports Med. Rep., Vol. 9, No. 5, pp. 314Y321, 2010. • Kerr et al. Epidemiology of Exertional Heat Illness Among U.S. High School Athletes Am J Prev Med 2013;44(1):8–14 • Wegmann et al. Pre-cooling and sports performance: A meta-analytical review. Sports Med. 2012;42(7);545-564. • Bennett et al. Wilderness Medical Society Practice Guidelines For Treatment of Exercise- Associated Hyponatremia. Wilderness Environ Med. 2013. In-press. • Hoffman et al. Hyponatremia in the 2009 161-km WSER. Int J Sports Physiol Perform. 2012;(7)1;6-10. Thank You