heat and hydration

as temperature increases

• the temperature gradient between air and the body decreases

when Tbody>Tenvion

we lose heat via radiation

typical body temp

37c - 98.6F

temp over 26 C

the body absorbs heat, heat loss is from evaporation only

heat is generated by ____ sources

endogenous sources

muscle activity and metabolism

when an athlete exercises in a hot envionement

they sweat to dissipate heat

an increase in humidity

will decrease the vapour gradient, therefore there will be less evaporation

• increased body temperature due to less evaporation of sweat

exertional heat stroke

occurs when the patient presents with exertion related hyperthermia and associated central nervous system disturbance or evidence of other end organ system damage

exertion related hyperthermia temp

core body temperature greater than 40c

individual and stopping sweating

• during EHS they may stop sweating but this is unreliable

• if they stop sweating this is bad because it means they’re trying to move blood around organs and cool off internally

experincing during ehs

• dizziness, weakness nausea, fast pulse and resp , mental confusion

• may collapse and become unconscious because body is shutting down

heat exhaustion is characterized by

an inability to continue functioning in the heat without evidence supporting the diagnosis of EHS

• signs and symptoms are variable and may inc

  • heavy sweating w/ pale, moist, cool skin

  • headache wekaness, dizziness, nausea (with/w/0 vomiting)

heat exhaustion non severe primary signs

• concious

• alert

• temp less than 40c

• systolic >100mmHg

Secondary signs of non severe (heat exhaustion)

• sweating

• pale, moist, cool skin

• cramping

• nausea

primary signs — heat stroke (Severe)

• unconsious or decreased mental status

• temp greater than 40c

• systolic < 100mmHg

secondary signs of severe heat stroke

• no sweat

• hot, dry skin

• weakness/flaccid

• nausea

management of heat injury - mild

• patient: alert w appropriate behaviour, near-normal/stable vital signs and able to drink fluids

• Care

  • on side line for up to one hour with up to 2 L fluid

  • rest in shade with reassessment every 5-10 min

  • does not improve? hospital

heat stroke management severe

• patient: mental status changes, amnesia, syncope, seizure, unable to drink, unstable, high temp

• Care

  • cool first transport second

  • agressive cooling within first ½ hour

    • remove gear, ice/water submersion (best) or on core starting w/ armpits and groin

  • rehydration

  • frequent vital signs and mental status assessment

  • evac to emergency

  • life threatening

intrinsic risk factors EHS *

• lack of acclimatization

• fever

• overweight/obesity

• dehydration

• recent alcohol use

• sunburn (can dehydrate ppl)

extrinsic risk factors EHS *

• Hot, humid environment

• Exercise intensity

• Inappropriate work-to-rest ratios

• Equipment/clothing

• Education

• athletes,

• Coaches and medical staff

• Lack of emergency plans to identify and treat EHS

• Lack of proper infrastructure (heat acclimatization)

• Access to fluids

• Access to preventative cooling strategies

combatting heat injuries concepts

• get an accurate temp

• get them cool

• allow acclimatization

• train coaches and players on signs

• keep them hydrated

getting an accurate temperature

• Know what we’re dealing with

• devices to measure core body temperature via direct contact with the forehead or radiation from the ear canal may not be accurate and are potentially dangerous (devices typically underestimate the temp)

• its ok to assume EHS if the patient is displaying signs even if the temp reading is slightly lower

keep them cool/get them cool

• cold water and ice water immersion provide superior cooling rates (temp dec 5-14 times faster than packing with ice)

• c100% effective in preventing death

amost ehs deaths

most ehs deaths occur among non-acclimatized players during the initial 3 days of summer

acclimatization improves cooling through

• increased sweating (evaporation)

  • less effective in high humidity

  • may need to add electrolytes if sweating a lot because we’re losing salt

acclimatization occurs by

progressive and prolonged elevation of the body core temperature

conditioned athletes acclimatize

after 4-7 progressive exercise sessions of 1-4 hours total duration each over a period of 1-2 week

Four high-intensity intermittent acclimation sessions, in a 10-day period, is sufficient to improve games-type exercise capacity.

living in a hot environment

without exercising in the environment provides little acclimatization

bottom lime acclimatization

• physiological adaptations will occur during 1-2 weeks of exercise heat exposure

• these include

  • reduced rectal temp, cardiovascular strain, and perceived exertion as well as inc plasma volume

the medical team (heat and hydration)

must educate staff and players on signs and symptoms and ensure EAPs are completed, understood and followed

• voice of reason

most ehs deaths in football

occur during practice

hypohydrated

• more than 50% of athletes arrive at training sessions hypohydrated

• and usually only replave 2/3 of sweat loss while training

excessive water deficit

The goal of drinking during exercise is to prevent excessive (>2% body weight loss from water deficit) dehydration and excessive changes in electrolyte balance to avert compromised performance

• greater than 2% means we’re probably dehydrated

facctors that contribute to the risk of hypohydration (extrinsic)*

• availability of fluids

• exercise structure

• sport specific factors

• env conditions

risk of hypohydration (Intrinsic factors) *

• sex

• thirst drive

• acclimatization status

• body size and comp

tracking hydration changes

1. Acute hydration changes can be measured by taking nude body mass before and after exercise (go pee first)

2. Check urine concentration/colour in the morning

3. thirst: first morning thise is correlated w/ hypohydration

hydration status can be reliably estimated

using as few as three consecutive days of first morning euhydrated body weights, measured after voiding

• if bm decreases more than 2% the individual is drinking too little, if it increases individual is drinking too much

thirsty at rest

means we’re already dehydrated

primary goal of rehydration

• the primary goal is the immediate return of physiological function

rehydration points

• compensate for urine losses by drinking (get what lost and then 50% over that)

• when recovery time is greater than 12 hrs athlete can eat and drink

• a balanced diet that provides 2500-3000 kcal will provide 1 litre of water per day from food alone so if they don’t wanna drink they can eat watery food (melons)

pre exercise hydration

start in a state of euhydration

hydration during exercise

• try to maintain water levels

• use CHO drink for periods greater than 1 hr

post exericse dluid

correct fluid loss ASAP

• much of this through general nutrition and H20, may need to add CHO and electrolytes

Hyponatremia

• An athlete who exercises for more than 4 hours and hydrates excessively (well beyond

  sweat loss) only with water or low-solute beverages may be susceptible to a relatively rare

  condition known as hyponatremia (also known as water intoxication)