environmental conditions

CV adaptations within one week of acclimatization

• increased plasma volume

• reduced heart rate

• improved stroke volume

• enhanced skin blood flow and sweating

• reduced core temp

sweating response to acclimatization

sweating changes take longer (2-3 weeks)

• earlier onset

• increased sweating rate

• reduced electrolyte loss

• lower body temp for sweating

• change in sweating location

• increased conversion of sodium

can be lost in 3-4 wks

Male unacclimatized to heat can sweat up to

1.5L/hr

Acclimatized male can have peak sweat rates…

above 2.5L/hr

Lower Body Temperature for Sweating

The body core temperature at which sweating begins decreases, allowing for more efficient cooling

Change in the sweating location

From chest and back to more on the lim

Increased conservation of sodium

From up to 60mmol/L to as low as 5mmol/L

thermoregulation

• body maintains a core temperature of ~37°C

• hypothalamus

hypothalamus regulation of core temp

Receives input from sensors in skin, mucous membranes (peripheral thermoreceptors) and internal structures (central thermoreceptors)

response to decrease in core body temp

heat response

• sweating

response to increase in core body temp

cooling response

• shivering

temp above 104

106-112 - heatstroke and brain lesions

5 step rectal temp

1. explain procedure and ensure privacy

2. position patient on side and put gloves on

3. lubricate and insert, 4in

4. measure and monitor

5. remove, clean, document

what temperature should the core temp be cooled to?

102

heat loss

• convection

• conduction

• evaporation

• radiation

convection

transfer of heat through a medium such as air or water (whirlpool)

conduction

transfer of heat through direct contact (ice bags, heat packs)

evaporation

dissipation of heat via removal of a conducting medium such as air (fans)

radiation

transfer of heat through a vacuum

• This is how the body loses the most heat, accounting for approximately 60% of heat loss under normal circumstances

hyperthermia

• elevated body temperature

Exposure to heat triggers increase in core body temperature

Sensors regulate this to the hypothalamus

Sympathetic nervous system activated

• Cutaneous vasodilation

• Sweat gland activation

where does body heat come?

• Muscle activity (breakdown of ATP)

• Increased muscle activity (e.g. exercise) results in more ATP being broken down, and more heat subsequently generated

% of heat production for muscle and skin during exercise

90%

Eccrine sweat glands

body temp regulation

• Apocrine glands (think ‘armpits’) produce a unique, oily secretion and are not effective at cooling the body

how are sweat glands activated?

via acetylcholine

% of sweat glands active at rest

5%

bead of sweat

Via chemical reactions, fluid is osmotically ‘pushed’ out of the gland to the skin, where we see it as a bead of sweat

factors that affect evaporation

Humidity

Temperature

Skin exposure (e.g. uniforms, clothing, etc.)

Activity level

• Can increase heat production ten-fold or more

Wind

• More airflow = more evaporation

components of sweat

• sodium

• potassium

• calcium

• magnesium

• trace metals

fluid replacement pre exercise

2-3 hours pre: 17 to 20 fluid oz

10- 20 min pre: 7-10 oz

fluid replacement during exercise

• Replacement should approximate sweat and urine loss

• Maintain hydration at less than 2% body weight reduction (7 to 10 ounces of water or sports drink every 10 to 20 minutes)

fluid replacement post exercise

• ingest fluid equal to 150% of the weight loss, ideally within two hours and no more than four to six hours after the event

Weight loss between practices

should be no more than 2-3%

• Any weight lost should be ‘regained’ prior to the next practice

oz to drink per pound od fluid loss during practice

15oz

heat index

• ‘How hot it feels’

• Marker of how well the body’s systems can collectively cool the body

• Combination of temperature and humidity

• Humidity decreases evaporation rates

  • Influences how much sweat can be evaporated

  • reduces the body’s cooling ability

• Does not factor in wind speed

dew point

• atmospheric temperature below which water droplets begin to condense and dew can form

• factor of relative humidity

  • When the air can't "hold" all the moisture (i.e. becomes saturated), then it condenses as dew

humidity

indicates the amount of moisture in the air compared to what the air can "hold" at that temperature

• indicates the ‘closeness’ of the temperature and dew point

condensation

temp is near the dew point

when does temp peak?

3-4:30pm

suns rays most direct btwn this time

11am- 1pm

Practice Guidelines in the Heat (NATA, 2002)

Acclimate 10-14 days

Increasing intensity

Acclimated athletes should train 1-2 hours in identical conditions as event

Match fluid intake with sweat and urine losses

If WBGT is >82F, move or delay event

Increased clothing should require a lower WBGT to modify practice schedule

Avoid scheduling during the hottest times of day

Think southern U.S. high school fall season practice times

Schedule adequate rest breaks

Supply ample fluids

Minimize clothing requirements

biometrics and sweat

• patch has a spiral microfluidic channel that wicks up the sweat

• The speed of the sweat through the channel provides a measure of the rate of sweating

• The channel takes the sweat to sensors that detect biomarkers such as potassium, sodium, and glucose

The biometric device

Monitors sweat, electrolyte loss and other factors, notifying workers when to take a break, hydrate or move to a shaded area

heat rash

• Thought to be due to blockage of sweat glands-

• Common in babies, but can occur in adults

• Hot, humid climates

• Often occurs under clothing

• Appearance of tiny dots or pimples

• Treatment – none required

heat cramps

•Thought to be caused by water/electrolyte loss

•True cause is not well understood

•Occurs more often with

• High heat/humidity

• Low acclimitization/training level

•Mainly occurs in the legs, but can occur anywhere

Treatment of heat cramps

• Cessation of physical activity

• Rehydration

  • Helps alleviate extended cramping

  • May take a while to have an effect

• Gentle passive stretching is most rapid and effective relief!

• Gentle massage

  • Should be a last step in the chain – likely to have little effect

• Beware of ‘snake oils’ – treatments that have no real effect but ‘sound’ great for preventing heat cramps

Heat exhaustion

• Occurs when the body cannot adequately cool itself during physical activity or exposure to a hot environment

• Precursor to heat stroke – recognition and intervention is key!

• Considered a preventable medical condition

  • Hydration

  • Monitoring of environmental conditions

• Body is trying all possible avenues to cool itself

• Not considered a medical emergency

  • Highly reversible if caught early enough

  • Dependent upon recognition timeframe and skill of the evaluator

heat exhaustion s/s

Heavy sweating Pale, cool, or clammy skin Elevated body temperature (typically below 104°F / 40°C) Fatigue or weakness Dizziness or lightheadedness Headache

Nausea or vomiting Muscle cramps Rapid pulse Excessive thirst Fainting or near-fainting Decreased exercise performance Difficulty concentrating or mild confusion

• Individuals with heat exhaustion generally do not have severe central nervous system dysfunction (such as seizures, unconsciousness, or profound confusion

• Any worsening mental status should raise concern for progression to heat stroke and requires immediate medical attention

heat exhaustion treatment

•Move to a cool environment

•Check and monitor all vital signs

•Monitor core body temp

•Remove excess clothing

•Cool using ice tub

•Cold towels, air flow (fan), ice packs if tub unavailable

•Rehydrate

heat stroke

• Most severe heat illness

• Occurs when the body's temperature regulation system fails, causing a dangerous rise in core body temperature

• Characterized by severe hyperthermia and central nervous system dysfunction

• Does not require heat exhaustion episode to occur first

• Medical emergency

• Can result in death

heat stroke s/s

• Bright red, hot, possibly dry skin

  • Depends on whether sweat still remains

• Very high core body temperature (>104F)

  • Exertional Heat Stroke (EHS) is often specifically classified at or above 105F)

• Little or no sweating representative of the activity

• Rapid pulse

  • Reported as either strong or weak

• Lethargic appearance

Heat stroke treatment

Call 9-1-1 immediately

Move athlete to a cooler area

Remove excess/saturated clothing

Increase air flow (fans, breeze)

Ice bath immersion

hypothermia

• body temperature below 95°C

• Cold receptors (peripheral and internal) activated

• Hypothalamus activates sympathetic response

Hypothalamus sympathetic response

•Cutaneous vasoconstriction

•Arrector pili contraction

•Epinephrine secretion from adrenal medulla

• Non-shivering thermogenesis (increased metabolism)

•Activation of the ‘primary motor center for shivering’ area of the hypothalamus

• Sends signals down the brainstem to the spine

• Spindles trigger a group of muscles to involuntarily contract

  • Contracture generates heat

    • Can increase metabolic rate four-fold

heat loss in the cold affected by

• Temperature

• Skin exposure

• Activity level

• Wind

Wind Chill

• Representation of how your body loses heat when factoring in temperature and wind

Chilblains

• Localized skin injuries that develop after repeated exposure to cold, damp conditions above freezing temperatures

• Damage occurs due to inflammation of small blood vessels in the skin

chillblains s/s

• Red or purple discoloration of the skin

• Itching or burning sensation

• Swelling

• Tenderness or pain

• Small blisters in some cases

• Most commonly affects fingers, toes, ears, and nose

immediate management of chillblains

• Remove the person from the cold environment

• Gradually warm the affected area

frostbite

• A localized cold injury in which body tissues freeze, resulting in damage to the skin and underlying structures

• Most commonly affects exposed areas such as the fingers, toes, ears, nose, and cheeks

frostbite s/s

• Cold, numb skin

• Tingling or burning sensation

• White, gray, yellow, or waxy-looking skin

• Loss of sensation

• Hard or frozen-feeling tissue

immediate management of frostbite

• Remove the person from the cold environment

• Protect the affected area from further injury

• Rewarm rapidly in warm water (98–104°F / 37–40°C) if refreezing can be prevented

• Refer for medical evaluation

hypothermia

A systemic cold injury that occurs when the body's core temperature falls below normal and the body can no longer generate enough heat to maintain proper function

Can become life-threatening if untreated

Affects the entire body and is defined by a dangerous reduction in core body temperature accompanied by progressive neurological and cardiovascular dysfunction

mild hypothermia s/s

Shivering

Cold skin

Fatigue

Difficulty performing tasks

Impaired judgment

Slowed thinking

moderate hypothermia s/s

Intense shivering or cessation of shivering

Confusion

Slurred speech

Loss of coordination

Drowsiness

Memory impairment

severe hypothermia

Significant alteration in mental status

Unconsciousness

Very slow heart rate

Slow breathing

Dilated pupils

Cardiac arrest

hypothermia immediate management

Remove the person from the cold environment

Remove wet clothing and replace with dry insulation

Provide warm blankets and shelter

Begin gradual rewarming

Offer warm fluids if the person is alert and able to swallow

Activate emergency medical services for moderate or severe hypothermia

Wet bulb globe temperature (WBGT)

Temperature

Humidity

Wind speed

Sun angle

Cloud cover

Sling psychrometer

Two thermometers

Air temperature

Wet-bulb temperature

Requires user to swing the top unit to obtain wet-bulb temp

Can calculate humidity

how many people are killed fromm lightning strikes in a year

20-50

what time of year do 90% of casualties ocurr?

may-sept

july with most victims

the mortality rate for lightning-strike victims

8% to 10%

• Most lightning deaths are due to cardiac or respiratory arrest at the time of injury