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Exertional Heat Stroke: Pathophysiology Discussion

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Epidemiology and Evidence. Risk factors. Signs. Dual ... EHI Mortality: Time at Temperature ... Hydration, WBGT based flags and acclimatization protection? ... – PowerPoint PPT presentation

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Title: Exertional Heat Stroke: Pathophysiology Discussion


1
Exertional Heat Stroke PathophysiologyDiscussio
n
  • Steve Blivin, MD, FAAFP, CAQSM
  • Commander, U.S. Navy
  • Head, Sports Medicine Department
  • Naval Hospital
  • Camp Lejeune, NC
  • ACSM/DOD Roundtable Conference
  • Exertional Heat Stroke
  • Bethesda, MD
  • 22-23 OCT 2008

2
Disclaimer
  • The following is my professional opinion based on
    the literature, unpublished data, experts
    opinions, and personal experience. It is not
    U.S. Navy or DoD official policy or opinion.

3
Agenda
  • Definitions
  • Epidemiology and Evidence
  • Risk factors
  • Signs
  • Dual pathway model
  • If true, what does it mean?
  • Pathophysiology discussion points and questions

4
Definitions Exertional Heat Injury (EHI)
  • Heat Exhaustion (HE)
  • Exerting AND
  • Cant go on, may be confused
  • Heat Stroke (HS)
  • Not strictly defined by Tgt104F (40C)
  • ExertingSx of HEAND
  • End Organ Damage
  • Mental Status Change
  • Study Abnormalities

5
EHI Data Okinawa (U.S. Military)
  • 2004 32 HE, 14 HS (1 death)
  • Stop Spray, Fan, Cool packs / Ice packs
  • Start Ice / Water cooling more Training
  • Model Parris Is. and Quantico USMC methods
  • 2005 16 HE, 4 HS
  • 1 HE discharged post muscle biopsy
  • 2006 26 HE, 4 HS
  • 2007 30 HE, 1 HS

6
EHI Mortality Time at Temperature
  • WWI Brits in Mesopotamia, 600 EHI (?deaths)
    until ice, water, and activity mods
  • WWII 200 DEATHS at US training bases
  • Parris Island, SC USMC Training
  • 1.5 (2/137) HS cardiac Mortality 1979-1990
    Paris Is.
  • Total HS mortality quoted 1 - 5 during this
    time
  • 0 Since ice water rapid cooling adopted
  • Quantico, VA USMC Training
  • 0 Since ice water rapid cooling adopted

7
Exertional Heat Illness Cases by Year and
Hospitalization 1979-97Parris Island, South
Carolina
Number of cases
8
Quantico Officer Candidate School EHI
9
Quantico EHI Candidates Dropped
  • 2000 10
  • 2001 6
  • 2002 10
  • 2003 11
  • 2004 2006 exact s not provided
  • All were from USMC Officer Candidate School (OCS)
  • 2003-2006 2 at risk for repeat HS and
    permanently NPQd
  • Candidates are dropped if not full duty gt 4 days
  • Many not motivated to return to full duty
  • Many return for a later class and graduate
  • USMC Officer The Basic School (TBS) had 1
    repeat EHI (HS with HE in past) who graduated to
    attend flight school.
  • Data reported by personal e-mail from CDR
    Scott Pyne (OCS / TBS 2000-2002) and CAPT Bruce
    Adams (OCS / TBS 2003-2007)

10
Quantico OCS EHI Data 2000-2002 Incomplete and
Retrospective
  • 6 (7) HS Dx in 82 total EHI data available
  • Data mostly missing for 50 out of ? HS
    transported (32) of 155 actual EHIs
  • All (100) of HS during 3 mile run (1 PFT)
  • HS Temp 106.1F (41.2C) to 107.8F (42.1C)
  • 17 of the 72 HE Dx had Tgt104F (40C)
  • 5 T gt 107F (41.7C)
  • 6 T gt 106F lt 107F (41.1C lt 41.7C)
  • 3 T gt 105F lt 106F (40.6C lt 41.1C)
  • 3 T gt 104F lt 105F (40C lt 40.6C)

11
Parris Is. Unpublished EHI Data 1998-99
  • No Dx noted on data. Mental Status not known.
    So, arbitrary HS CKgt3K and/or ASTgt100
  • 32 HS in 142 EHI (23) by labs alone
  • 10 HS had Temp lt 104F (40C)
  • Range 97.9F (36.6C) to 103.1F (39.5C)
  • T101F (38.3C), CK6K, AST209
  • 21 HE T gt 104F (40C)some probably HS by mental
    status
  • 1 T 109.2F (42.9C)normal labs common in HS
    with rapid cooling
  • 3 T gt 107F lt 109F (41.7C lt 42.9C)
  • 3 T gt 106F lt 107F (41.1C lt 41.7C)
  • 7 T gt 105F lt 106F (40.6C lt 41.1C)
  • 7 T gt 104F lt 105F (40C lt 40.6C)

12
Temperature
  • Level of core temperature elevation NOT
    diagnostic of HS
  • Parris Is. study - 468 EHI cases
  • 1/2 cases with HS had Tlt 106F (41.5C)
  • 1/2 cases with Tgt106F (41.5C) had HS

13
Thermoregulation ? Thermo-tolerance
Byrne, Lee, Tan and Lim MSSE (38 803-810, 2006)
14
(No Transcript)
15
EHI Risk Factors Environment
  • Competitive or group activities peer pressure
  • Kevlar, Flak, Packadd 10F (5.6C) to WBGT
  • HUMID, sunny, hot (WBGT Flag system)
  • Most EHI occur at WBGT 70F 85F (21.1C 29.4C)
  • Military Heat Stress Flags
  • Green 80F 85F (26.7C -29.4C) , Yellow 85F - 88F
    (26.7C 31.1C), Red 88F 90F (31.1C 32.2C)
    Activity cautions
  • Black 90F (32.2C) Activity suspended unless
    required
  • NOTE ACSM black flag starts at 82F (27.8C)
  • Preceding day MAX heat stress
  • Most EHI had preceding day WBGTMAX gt85F (29.4C)

16
Exertional Heat Illness Cases by Hour 1982 -
1996 (excluding 1992)Parris Island, South
Carolina
Number of cases
0800
1500
17
EHI Risk Factors Personal
  • Overweight
  • BMI 22-26 (OR 1.7)
  • BMI gt26 (OR 3.6)
  • Slow gt8 min/mile runner (OR 5.6)
  • Overexertion (pushing beyond ability)
  • Febrile, GI, or Respiratory illness
  • Dietary Supplements, Drugs
  • Dehydration, Prior EHI, poor acclimatization
  • In literature but not noted in recent deaths or
    EHS cases70-100 acclimatized, fully/over
    hydrated.

18
EHI Signs (think heat stroke)
  • Trect 103F to 110F (39.4C to 43.3C)
  • If Tlt103F think other Dx like hyponatremia
  • Tachycardia /-
  • Hypotension /-
  • SWEATING. NOT DRY (as in classic heat stroke)
  • All EHS victims sweat in Quantico, Parris Is, and
    Okinawa. - Survey of all Navy sports docs 2006
  • Mental Status Change Obtunded, Giddy, Crying,
    Combative
  • Collapse
  • Seizure

19
Immune Response to Intense Exercise
Open Window Theory
Intense exercise
Intense exercise
Immune function
Intense exercise
Normal immune function
Exercise
Suppressed Immune function
3 to 72 h
Suppressed Immune function
Chronically suppressed immune function
Post-exercise
Time
Smith L.L. Sports Med. 33347-364, 2003
20
Working Hypothesis
Heat sepsis triggers the primary pathway of heat
stroke
Heat intolerance results from a transient shift
in physiological state
Heat Stroke
Direct thermal effect drives the secondary
pathway of heat stroke
Exercise- induced immune changes
Pre-existing or sub-clinical infection
Facilitator
Pathology
Outcome HS
Heat
Sepsis
Clinical state
21
USMC Marathon October 2001Pentagon
22
If true, what does it mean?
  • Dual pathway theory supported 1. SIRS likely.
    2. Direct heat damage over time possible.
  • T97F with EHS
  • Tgt106F not always EHS.
  • Rapid ice-water cooling prevents sequela even at
    T110.5F (Quantico 2006)
  • Role for cooling in other SIRS?
  • Prior EHS not a risk factor for future EHS?
  • No repeat EHScould prior EHS protect against
    future EHS?
  • Role of heat tolerance testing?
  • Hydration, WBGT based flags and acclimatization
    protection?
  • Increased performance increased EHS risk
  • Decreased performance decreased EHS risk
  • EHS not a sweating failure.
  • EHS victims SWEAT in hot, humid environments

23
Questions?
24
REFERENCES
  • 1. Lim CL, Mackinnon LT. The Roles of Exercise
    induced Immune system Disturbances in the
    Pathology of Heat Stroke. The Dual pathway Model
    of Heat Stroke. Sports Med 2006 36(1) 39-64
  • 2. Lim Cl et al. Preexisting inflammatory state
    compromises Heat Tolerance in Rats Exposed to
    Heat Stress. Am J Physio- Regulatory,
    Integrative and Comp Physiol. 2007 292 16-194
  • 3. Ng QY et al. Plasma Endotoxin and Immune
    Responses During a 21-Km Road Race Under a Warm
    and Humid Environment. Ann Acad Med Singapore
    2008 37 307-14
  • 4. Lim Cl. Heat Injury Prevention The Singapore
    Experience. Presented at Heat Lessons Learnt or
    Ignored Seminar. Australian Department of
    Defence.  Canberra AU. 20 NOV 2006.
  • 5. Cotter J. Heat Injury Pathophysiology.
    Presented at Heat Lessons Learnt or Ignored
    Seminar. Australian Department of Defence. 
    Canberra AU. 20 NOV 2006.
  • 6. Holtzhausen L Noakes TD, KorningB, et al.
    Clinical and biochemical characteristics of
    collapsed ultramarathon runners. Med Sci Sports
    Exerc 1994261095-1101.
  • 7. Laird RH Medical care at ultraendurance
    athlete proposed mechanisms and approach to
    management. Clin J Sports Med 1997(4)292-301.
  • 8. Holtzhausen L Noakes TD, Collapsed
    ultraendurance athlete proposed mechanisms and
    an approach to management. Clin J Sports Med
    19977(4)292-301.
  • 9. Sandor RP Heat illness. Phys and Sports Med
    199725(6).
  • 10. Gardner JW, Kark JA Heat-associated illness.
    In Strickland GL. Hunters Tropical Medicine.
    8th ed. 2000140-147.
  • 11. BMC Parris Island 2000 Clinical Guidelines
    for Management of EHI Based on Symptoms and
    Clinical Chemistry Presentation.
  • 12. Environmental illness in athletes. Seto CK -
    Clin Sports Med - 01-JUL-2005 24(3) 695-718, x
  • 13. Gardner JW, Kark JA, Wenger BC et al.
    Exertional Heat Illness in U.S. Marine Recruits,
    presentation (no date) 1990s
  • 14. Personal communication and U.S. Marine Corps
    and Navy Exertional Heat Injury experience survey
    including all Navy Sports Medicine Physicians
    with Steve Blivin. NOV 2006 and OCT 2007.
  • 15. Byrne C, Lee JKW, Chew SAN et al. Continuous
    Thermoregulatory Responses to Mass-Participation
    Distance Running in Heat.. Med Sci Sports Exerc
    38(5) pp 803-810, 2006
  • 16. Gardner JW, Gutmann FD, Potter RN, Kark JA.
    Nontraumatic exercise-related deaths in the U.S.
    military, 1996-1999. Mil Medicine. 167
    (12)964-70, Dec. 2002
  • 17. Gaffin SL, Gardner JW, Flinn SD. Cooling
    Methods for Heatstoke Victims. Ltr to editor.
    Annals Int Med. 132(8) pp678-9, 18 APR 200021.
  • 18. Climatic Injuries in the Armed Forces
    Prevention and Treatment 2003. Defense Medical
    Services Department, Ministries of Defense (U.K.)
  • 19. Personal Communications Dr. Jim Cotter,
    Exercise and Environmental Physiology, University
    of Otago, Duedin, New Zealand with Dr Steve
    Blivin OCT 08.
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