Hyperthermia: Recognizing and treating heat related illness - BRIAN G. COLLINS, MSPAS, PA-C

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
    Core temp set point 37oC ±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
                                                    Consider tox screen, CT head & LP
     experiencing heat stroke because
     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

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

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 OK

Moving forward

    Expect temperature intolerance
    Return to activity REQUIRES:
        1 week of rest
        Confirmed recovery
        Acclimatization
        Consider previously mentioned ACSM guideline

Is it supposed to be this hot all
summer long?
STRATEGIES FOR PREVENTION

Preparation is key

  Know   your risk
  Acclimatization
  Situational   awareness
  Hydrate,   hydrate, hydrate

Know your risk

    Certain factors increase risk of heat illness:
        Individual characteristics
        Medical conditions
        Medications
        Social determinants

Acclimatization

    Gradual increase in duration and intensity of daily activity
    10–14 days of exposure
    Gradual phase-in of protective equipment
    Permits time to match fitness levels to level of exertion
    Event-specific exercise helps
    No permanent effect*

 Take home: The first 2-3 weeks of preseason practice
 represents the most dangerous period of risk for exercise
 induced heat illness

Situational awareness:
Wet Bulb Globe Temperature (WBGT)
    Taken by a thermometer with a bulb covered by a
     water-soaked cloth*
    Measure of overall heat stress in direct sunlight
        Accounts for temperature, humidity, wind speed, sun angle, and
         cloud cover
        More accurate estimate than heat index
        Accurate determination of on-site risk

Hydration

    Goal:
        Drink enough throughout the day to keep early morning urine
         clear
        Drink enough during exercise to prevent more than 2% body
         mass loss
    Ensure at least some sodium replenishment in food/drink
     if sweating

Questions?

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