Hyperthermia: Recognizing and treating heat related illness BRIAN G. COLLINS, MSPAS, PA-C Who are You? (who, who?) EMS 2007-2012 Emergency Management – Departments of Military Affairs, Virginia and Washington, DC (2011-2016) Shenandoah University PA Program – Class of 2016 Private outpatient internal and occupational medicine practice – 2017- 2018 Critical access medicine, Avera Gregory – 2018-Present Black Hill VA contracted medical staff – 2018-Present I have no financial disclosures Intended Audience Physicians, PAs, and NPs working in Primary Care, Urgent Care, Sideline Medicine, and Emergency Department settings Medical, PA, and NP students aspiring to work in these same settings Learning Objectives At the conclusion of this activity, participants will be familiar with: • The spectrum of illness associated with heat exposure in adolescents & adults • Diagnostic and management approach to heat illness in adolescents & adults • Considerations related to pediatric populations • Strategies for prevention of heat illness Man it’s a hot one SPECTRUM OF HEAT ILLNESS Brief review of thermoregulation Hypothalamic control o Core temp set point 37 C ±1 Body tolerates cold better than heat Multiple mechanisms of thermoregulation: Evaporation* Radiation* Convection Conduction How these mechanisms fail Ambient temperature higher than body temp Convection, conduction, and radiation fail High humidity (relative humidity >75%) Evaporation fails Others Deadly Heat Critical Thermal Maximum (CTM): the minimal high deep-body temperature that is lethal to an animal Human CMT: 42oC (107.6oF) for 45 minutes to 8 hours For each 1°C rise in tissue temperature above 42°C, the time required for an equivalent effect is halved Cell injury occurs through multiple mechanisms: Inflammatory cascade Uncoupling of oxidative phosphorylation Protein denaturation multi-organ failure Impaired microcirculation and DIC Intestinal ischemia and increased permeability Basic concept Heat syncope Heat Heat Heat cramps exhaustion stroke Heat injury I can’t take it no more it’s a hundred degrees DIAGNOSIS AND MANAGEMENT A note regarding thermometry Rectal temperature is the gold standard for checking core temperature when exertional heat stroke is suspected* Other methods? Temporal? No correlation in hyperthermia Tympanic? Underestimate CBT as it rises Oral? Less consistent as CBT rises Time is tissue Exertional vs non-exertional NB: Heat illness can occur without exertion Risk factors: Obesity Extremes of age Dehydration Chronic illness (esp DM, cardiovascular dz) Acute illness (multiple factors) ETOH abuse Medication use* Approach remains (essentially) the same Heat Cramps Etiology: Dehydration Electrolyte depletion Extreme conditions Neurogenic fatigue Diagnosis: Intense pain w/ cramping in overused muscle not associated w/ injury No evidence of more severe illness Core temp: Normal Management: Hydrate with attention to electrolyte repletion Stretching can help relieve acute discomfort Check serum sodium if persistent/recurrent cramping Heat syncope (Exercise Associated Collapse) Definition: Inability to stand or walk without assistance due to dizziness lightheadedness or syncope Following completion of an exertional event Etiology: Exertional: Extended periods of exertion leads to significant venous dilation. Non-exertional: Prolonged exposure to high environmental temps without proper acclimatization Core temp: normal or only mildly elevated Treatment: Treat potential emergent causes of collapse (heat stroke, ACS, anaphylaxis, etc) Reverse Trendelenburg Fluids Sodium and glucose testing, treat if low, transfer to ED if no improvement after 30 minutes Heat Syncope Exertional Non-exertional Heat exhaustion Definition/Diagnosis: Obvious difficulty continuing with exertion Core temp: 38.3 to 40oC (101 to 104oF) No significant CNS dysfunction* Management: Remove from the hot/humid environment Reverse Trendelenburg Rehydrate (water, sports drink, etc) Cooling until CBT is ~101oF (38.3oC) Frequent vitals Transport to ED if no rapid improvement despite appropriate therapy After: Hold from activity for 24-48hrs, then slow graduated return to activity Heat Injury Middle ground between heat exhaustion and heat stroke Definition: Collapse during strenuous activity Hyperthermia + Evidence of end-organ damage No CNS dysfunction Treatment: Monitor renal function, liver enzymes & function, urine myoglobin, CK Hospital admission criteria the same as for heat stroke After: Hold from participation until normalization of the above labs Heat stroke: Diagnosis Two core criteria*: Diagnostics: Core temp: >40oC (104oF) Rectal temperature + CNS dysfunction CBC Variable symptomatology aside from CMP, coag panel CNS dysfunction CK, urine myoglobin Accompanied by organ/tissue Chest x-ray damage ABGs Outcomes tied to time above 40oC LDH Myth dispelled: Do NOT assume that a Blood cultures diaphoretic patient is not experiencing heat stroke because Consider tox screen, CT head & LP they “haven’t stopped sweating” Differential is broad, keep your mind open Heat stroke: Management Support ABCs Rapid cooling (method depends on Classic vs Exertional) ASAP or within 30 minutes of presentation Initiate cooling WHILE removing clothing Constant CBT monitoring* Stop when CBT reaches <39oC (102.2oF) Shivering is NOT a reliable indicator IV benzos for shivering and seizure treatment/prevention Cold Water Immersion (CWI) • Begin immediately, remove clothing as able but do not delay cooling • Water temp should be ~35 – 59oF (1.7-15oC), constantly circulated • Immerse up to the neck if able, otherwise immerse as much as possible and augment with cold towels or dousing w/o fanning • Expect 1oC drop every 5 minutes (1oF every 3 minutes) Tarp-Assisted Cooling Oscillation (TACO) • Best option if immersion tub not available • Requires tarp, 10 gal ice, 20 gal water, and 3 or more people • Ice and water over the feet, head up, oscillate the sides • Body temp drops ~1oC every 6 minutes, adequate alternative • Not as well studied as CWI Evaporative External Cooling • Remove clothing (no sheets either) • Spray the patient with tepid water and utilize fan(s) • Can add cold packs to large vessel areas to augment cooling • Expect drop of 1oC every 10 minutes Heat stroke: Management Supportive care as indicated for underlying processes IV benzos for seizure treatment/prevention and for shivering* Isotonic saline for hyponatremia and volume repletion Treatments NOT proven effective Antipyretics (toxic, do NOT administer) Chilled IV fluids, cold internal lavage, or cooling blankets (as primary methods) Dantrolene Admission: Experts recommend minimum 24-48hr hospital observation for ALL, but especially… Persistent vital sign / mental status changes despite appropriate treatment At increased risk for severe complications ICU If signs of multi-organ dysfunction Length of hospitalization dependent on severity/extent of end organ damage Sequelae Pulmonary Renal Cardiovascular Neurovascular Hepatic Systemic Moving Forward ACSM guidelines for athlete return to play: No exercise for at least 7 days after release from medical care Follow-up with medical team 1 week after release for exam and lab recheck and imaging as indicated based on organ systems involved initially Once cleared, activity is begun in a cool environment with gradual increase in duration intensity and heat exposure over the course of at least 2 weeks Those unable to resume vigorous activity after 4 weeks should be re- evaluated Full return to play once able to participate in full activity in the heat for 2-4 weeks without adverse effects Moving Forward No consensus guidelines for general population Recovery in general will take similar steps Gradual return to prior level of activity Rehab Medication considerations Specialist involvement Heat Stroke: Case study Down in the playground, the hot concrete CONSIDERATIONS RELATED TO PEDIATRIC POPULATIONS Children are not “little adults” Anatomical and physiological differences Increased heat production Higher body surface to mass ratio Smaller blood volume Lower cardiac output per metabolic rate Lower rate of sweating Higher sweating set point Slower rate of acclimatization In general, they lack adult-level dexterity* Less attention to hydration Public Service Announcement Pediatric spectrum Heat syncope Heat Heat Heat rash Heat stroke cramps exhaustion Heat tetany Heat rash (aka “Miliaria”) Multiple forms Benign condition Treatment: Remove to a cooler environment Reduce sweating Treat associated pruritus (if present) OTC lotions Topical corticosteroids PO antihistamines Heat tetany Similar to heat cramps: Muscle spasms Exertion Normal CBT Different from heat cramps: Respiratory alkalosis Circumoral paresthesias and upper extremity spasm Not necessarily exertional Treatment: Remove from heat Partial rebreather mask with O2 <5Lpm Consider benzodiazepines for refractory cases* Heat exhaustion Diagnosis criteria slightly differs from adolescents/adults: ANY elevation of core body temperature above 37oC up to 40oC (with known heat exposure) NO CNS changes* Treatment remains the same Heat Stroke Diagnostic criteria & treatment remain the same Preferred methods of cooling differ In the ER: Evaporative external cooling preferred* Cold-water immersion second-line Outside of the ER: Whichever is most readily available Adjunctive methods