Transcript Evaluation of Environmental Injuries

Evaluation of
Heat Illness
Physiology of
Temperature Regulation
• Hypothalamus
– Center for thermal
regulation
– integrates input
from thermal
receptors
– Sends autonomic
impulses to increase
vasodilation /
vasoconstriction to
periphery and cause
sweating / shivering
Body Temperature
• Determined by balance
between heat
production (BMR,
muscular activity) and
heat loss
• Environmental
conditions can make
98.6° difficult to
maintain
Mechanisms to Promote
Heat Loss
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Conduction
Convection
Evaporation
Radiation
S = M +/- R +/- K +/- Cv - E
Assumptions
• Convection, and radiation are very
effective when external temp is
lower than 87°
• If external temp is higher than body
temp, heat transfer is reversed
• Evaporation becomes primary
method
• The more humidity, the less effective
evaporation becomes. (Big decrease
when >60%).
Sweat Rates
• Up to 2 liters per hour
• 2% body weight
impairs performance
• Thirst not a good
indicator of hydration
status
• 1L of sweat = 1.25L
ingested beverage
• < 50% of fluid lost is
typically replaced
Electrolyte Losses
• Na+, Cl-, K+,
Mg+
• Na – main one –
muscle cramps
• Typical
American diet
replaces most
electrolytes
Heat Exposure
Syndromes
• Traditional
– Heat Cramps
– Heat Exhaustion
– Heat Stroke
• New Classifications
– Heat Syncope
– Exertional
Hyponatremia
Heat Cramps
• Water loss vs
Electrolyte loss?
• Athletes most at
risk have a Hx
• Extremities &
abdominals
Rx for Heat Cramps
• Fluid replacement
w/ Na
• Gentle Stretching
and Massage
• Lie Down to
increase blood flow
to the legs
• Ice
Heat Syncope
• AKA “Orthostatic
Dizziness”
• Caused by
peripheral
vasodilation,
postural pooling of
blood, decreased
venous return and
Q
• 1st 5 days before
acclimatized
Heat Syncope
Recognition
• Brief episode of dizziness
associated with tunnel vision, pale
or sweaty skin, decreased pulse
• Normal Temp (97-104°)
Heat Exhaustion
• AKA “Heat
Prostration”
• Caused by inadequate
CV response
– brain vs skin vs
muscles
– Dehydration
decreases blood
volume
Heat Syncope Rx
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Shade
Monitor Vitals
Elevate Legs
Rehydrate
Signs and Symptoms of
Heat Exhaustion
• Hypovolemic Shock
• Sx vary in severity and number
• Weakness, fatigue, dizziness, headache,
loss of appetite, nausea, pallor, profuse
sweating, vomiting, urge to defecate,
syncope, thirsty, irritable
• Can be difficult to distinguish from Heat
Stroke w/ out rectal temp
• Body Core Temp ranges from 97-104°
• Assess cognitive skills to rule more
serious conditions
Rx for Heat Exhaustion
• Rest in Cool
• Fluid Replacement
– Ingesting
– IV
• Electrolyte
Replacement
• Supine Posture
• Remove excessive
clothing
• Cold Buckets / Fans
Heat Stroke
• Body’s cooling
mechanisms have failed
leading to hyperpyrexia
(body temp > 104°)
• Anhidrosis – body stops
sweating
• Causes damage to CNS
and internal organs
• May develop suddenly or
progress from heat
exhaustion
• Medical Emergency
Signs and Symptoms of
Heat Stroke
• Hot, dry skin
• Decreasing BP
• Rapid, full pulse
becomes rapid,
weak
• Vomiting, diarrhea,
seizures, coma
• Poor cognitive
function
• Multiple organ
failure
Conditions Resulting
from Heat Stroke
• Lactic Acidosis
• Hyperkalemia
(excessive K+)
• Renal Failure
• Disseminated
Intervascular
Coagulaton
Rx for Heat Stroke
• Cooling immediately
– immerse in cold
bath (35-59 degrees)
to reduce body temp
to < 100°
– Remove from pool
when body temp
reaches 101°
• Use wet towels /ice
bags and fanning in
transport to hospital
• Treat for shock
Exertional Hyponatremia
• Rare?
• Low serum-Na level (< 130mmol/L)
• Ingest too much water vs ingest too little
Na?
• Sx – disorientation, headache, vomiting,
lethargy, swelling of extremities,
pulmonary and cerebral edema, seizures
• Results in death if not treated by
rehydrating w/ fluids w/ Na
Reducing Risk of Heat Illness
• Pre-participation
Physical /
Screening
• Early Recognition
of Sx
• Conditioning
• Acclimatization
– 4–7 days vs 10-14
days vs months?
– After 6 weeks able
to produce 2.5x
normal amount of
sweat
– Diminishes by day 6
of inactivity
Reducing Risk (con’t)
• Educate players
and coaches
• Diet – extra Na+
• Rest and Digest
• Monitor urine color
and amount
• Weigh in and out
• Clothing /
Equipment
modifications
Reducing Risk (con’t)
• Stay well
hydrated (NATA Position
Statement: Fluid Replacement )
– Pre: 17-20oz, 2-3
hours before and
7-10oz.
– 20 min before
– During: 7-10oz
every 20 min
– Replace lost fluid
Reducing Risk
– Beverage Temp
50-59°
– Beverage Choice
• Water
• 6-8% CHO
solution if longer
than 45 mins
• No Caffeine,
alcohol
• .3-.7g/L Salt (esp
1st 3-5 days)
(con’t)
Reducing Risk (con’t)
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Fans
Shade
Cold buckets
Cold Tub
Thermometer
BP Cuff
Telephone
Predisposing Medical
Conditions for Heat Illness
• Sickle Cell Trait –
carry less O2
• Cystic Fibrosis Trait –
increases salt loss in
sweat
• Arteriosclerotic
Vascular Disease –
thicker arterial walls
decrease blood flow
• Scleroderma – skin
disorder that increases
sweating
Predisposing Medical
Conditions for Heat Illness
• Drug / Supplement
Use – Ephedra
– Diuretics
– Antidepressants
decrease sweating
– Beta blockers reduce
skin blood flow
– Antihistamines
constrict blood vessels.
(con’t)
Recommendations
National Weather Service
Recommendations
• Cease activity
when Heat index
is over 105°
• Heat index only
includes
temperature and
humidity
Instruments to Evaluate
Hot/Humid Environments
WBGT
Sling/Digital Pyschomoter
Temperature
& Humidity
Temperature, humidity, radiant heat, and air movement
WBGT=.1(DBT)+ .7(WBT)+.2(GT)
WBGT = .7(WBT) + .3(DBT)
Event and Practice Guidelines
Arnheim & Prentice, 1993
– Watch the Obese
• 80-90 degrees & < 70% humidity
– Take a 10 min rest every hour, change t-shirts
when wet, watch all athletes
• 80-90 degrees and > 70% or 90-100 degrees
and < 70%
– Suspend practice
• > 100 degrees or > 90 degrees & humidity over
70%
WBGT > 90 No training, skull sessions
NATA Position Statement Activity
Modification Guidelines Using WBGT
Event and Practice Guidelines
(NATA Position Statement:
Exertional Heat, 2002)
• Wet Bulb Globe Temperature
– WBGT > 82, reschedule, if possible
Even in the South? We’d never practice!
Disclaimer
• “Certified athletic trainers work in a variety of
professional and geographic settings….. obviously
the ATC in Florida will adapt the recommendations
to his or her environment, while the ATC in Maine
will make different adjustments.” - Casa
• “Athletic trainers should recognize that temperature
ranges might vary widely based upon geographic
regions. Athletic trainers may practice in regions,
such as the southeastern United States, where the
WBGT is routinely in the high or extreme or
hazardous level of risk throughout a significant part
of the year. In these regions, while it may not be
practical to reschedule or delay events, the athletic
trainer must recognize that the level of risk is high
and take appropriate steps to reduce risk.” – NATA
NATA Position Statement Activity
Modification Guidelines using
Temp and Humidity
• Add 5 degrees to temp
on bright sunny days
bwtn 10 and 4
• Lt of triangles - Full
gear
• Rt of circles - walk-thru
• Btwn squares and
circles - break every
15-20 min & shorts only
• Bwtn triangles and
squares - break every
20-30 min & helmet and
shoulder pads
Risk of Heat Exhaustion in
Hot/Humid Environments
Take a look at the InterAssociation Task Force
Heat Illness Consensus
Statement
Inter-Association Task Force on
Exertional Heat Illnesses
Consensus Statement (June 2004)
These guidelines were established to increase safety and
performance for individuals engaged in physical activity,
especially in warm and hot environments. The risks
associated with exercise in the heat are well
documented, but policies and procedures often do not
reflect current state-of-the-art knowledge. Many cases of
exertional heat illness are preventable and can be
successfully treated if onsite personnel identify the
condition and implement appropriate care in a timely
manner. Strategies to optimize proper care of
dehydration, exertional heat stroke (EHS), heat
exhaustion, heat cramps and exertional hyponatremia are
presented here. This consensus statement was developed
by medical / scientific experts experienced in the
prevention, recognition and treatment of exertional heat
illnesses.
Return to Play Criteria
for Dehydration
• A nauseated or vomiting athlete
should seek medical attention to
replace fluids via an intravenous line.
• Return-to-Play Considerations
– If the degree of dehydration is minor and
the athlete is symptom free, continued
participation is acceptable. The athlete
must maintain hydration status and
should receive periodic checks from
onsite medical personnel.
Return-to-Play Considerations
After Heat Stroke
Physiological changes may occur after an episode of
EHS. Heat tolerance may be compromised.
The following guidelines are recommended for returnto-play after EHS:
• Physician clearance: Avoid exercise until
completely asymptomatic & lab tests are normal.
• Severity of the incident should dictate the length of
recovery time.
• Avoid exercise for the minimum of 1 week after
release from medical care.
• Gradual return to physical activity.
Return-to-Play Considerations
After Heat Stroke (con’t)
Type and length of exercise should be determined by the
athlete's physician and might follow this pattern:
1. Easy-to-moderate exercise in a climate controlled
environment for several days, followed by strenuous
exercise in a climate-controlled environment for several
days.
2. Easy-to-moderate exercise in heat for several days,
followed by strenuous exercise in heat for several days.
3. (If applicable) Easy-to-moderate exercise in heat with
equipment for several days, followed by strenuous
exercise in heat with equipment for several days.
Return to Play Criteria
for Heat Exhaustion
• No Sx and fully hydrated.
• Recommend physician clearance
or, at minimum, a discussion w/
supervising physician before
return.
• Rule out underlying condition or
illness that predisposed athlete
for continued problems.
Return to Play Criteria
for Heat Exhaustion (con’t)
• Avoid intense practice in heat until at least
the next day to ensure recovery from
fatigue & dehydration. (In severe cases,
intense practice in heat should be delayed
for > 1 day.)
• If underlying cause was lack of
acclimatization and/or fitness level, correct
this problem before athlete returns to fullintensity training in heat (especially in
sports with equipment).
Return to Play Guidelines
for Heat Cramps
• Perform at the level needed for
successful participation?
• Review
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Diet
Rehydration practices
Electrolyte consumption
Fitness status
Level of acclimatization
Use of dietary supplements
Return to Play Criteria for
Exertional Hyponatriema
• Physician clearance
• Mild cases, activity can resume a
few days after completing an
educational session on establishing
an individual-specific hydration
protocol
– ensures proper amount and type of
beverages and meals are consumed
before, during and after physical activity
(see Table 2).
References
•
Arnheim D.D. & Prentice W.E. (1993). Principles of Athletic
Training. (8th ed.) St. Louis: Mosby-Year Book.
•
American Academy of Orthopaedic Surgeons. (1999). Athletic
Training and Sports Medicine. (3rd ed.)
•
Binkley HM, Beckett, Casa DJ, Kleiner DM, Plummer PE. (2002).
National Athletic Trainers’ Association Position Statement:
exertional heat illness. Journal of Athletic Training, 37(3):329343.
•
Casa DJ, Armstrong LE, Hillman SK, Montain SJ, Reiff RV, Rich
BS, Roberts WO, Stone JA. (2000). National Athletic Trainers’
Association Position Statement: fluid replacement for athletes.
Journal of Athletic Training, 35(2):212-224.
•
Inter-Association Task Force on Exertional Heat Illness
Consensus Statement (2004). www.nata.org