Fluids, Electrolytes and Hydrationforms.acsm.org/TPC/PDFs/12 Heiman.pdf · Fluids, Electrolytes and...

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Fluids, Electrolytes and Hydration Diana Heiman, MD Associate Professor, Family Medicine Residency Director East Tennessee State University

Transcript of Fluids, Electrolytes and Hydrationforms.acsm.org/TPC/PDFs/12 Heiman.pdf · Fluids, Electrolytes and...

Page 1: Fluids, Electrolytes and Hydrationforms.acsm.org/TPC/PDFs/12 Heiman.pdf · Fluids, Electrolytes and Hydration ... dehydration on exercise ... Performance decreases with water loss

Fluids, Electrolytes and

Hydration

Diana Heiman, MD

Associate Professor, Family Medicine Residency Director

East Tennessee State University

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Objectives

Discuss optimum hydration and effects of

dehydration on exercise

Discuss the best methods for fluid replacement

Review the electrolyte composition of sports

drinks

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Optimum Hydration

Performance decreases with water loss of 2% or more of body weight

Prehydration prior to exercise helps avoid excessive losses during exercise (goal to be euvolemic)

Measuring body weight prior to and after exercise can estimate sweat rates

Electrolytes also need to be replaced – more or less depending on sweat rate and salt content

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* increased losses with increased sweat

rate and dehydration

Sweat

Major means of cooling the exercising body

Losses vary greatly person to person and with different types of activities

Contains: Water

Electrolytes Sodium *

Potassium

Calcium

Magnesium

Chloride *

Electrolytes must be replaced

Excessive salty sweating can lead to hyponatremia

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Sweat

Water loss (sweat) during exercise is dependent

on:

Exercise intensity

Ambient temperature and humidity

Clothing

Body surface area/body weight

Acclimatization

Metabolic efficiency in the exercise

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Hourly Sweat Rates

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Sweat

1L of sweat loss

= 1 kg body weight loss

= ~580 kcal loss

Page 8: Fluids, Electrolytes and Hydrationforms.acsm.org/TPC/PDFs/12 Heiman.pdf · Fluids, Electrolytes and Hydration ... dehydration on exercise ... Performance decreases with water loss

ACSM Position Stand on Exercise and

Fluid Replacement 2007

Sweat Rates in Different Sports

Page 9: Fluids, Electrolytes and Hydrationforms.acsm.org/TPC/PDFs/12 Heiman.pdf · Fluids, Electrolytes and Hydration ... dehydration on exercise ... Performance decreases with water loss

ACSM Position Stand on Exercise and

Fluid Replacement 2007

Measures of Hydration Status

Urine measures not accurate during rehydration.

Page 10: Fluids, Electrolytes and Hydrationforms.acsm.org/TPC/PDFs/12 Heiman.pdf · Fluids, Electrolytes and Hydration ... dehydration on exercise ... Performance decreases with water loss

Measures of Hydration Status

Can’t rely on thirst, dizziness, headache,

tachycardia, dry mouth, skin turgor to predict

dehydration

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Effects of Dehydration on

Performance

With dehydration: increased strain and perceived exertion for the same task

Exaggerated in warm-hot conditions and with greater degree of dehydration

Less effect of dehydration seen in cold conditions

Dehydration (>2% BW) decreases aerobic performance, especially in warm-hot conditions

Dehydration (>2% BW) may decrease mental/cognitive performance

Dehydration (3-5% BW) doesn’t decrease anaerobic performance or muscle strength

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Dangers of Impaired Fluid Balance

Dehydration

Increases risk for

exertional heat illness

Muscle cramps (salty

sweaters)

Increases risk for renal

damage with

rhabdomyolysis

Hyperhydration

Hyponatremia – free

water intake greater than

sweat loss or large sweat

sodium losses

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Exercise-Associated

Hyponatremia First recognized in the comrades marathon (South

Africa, reported in 1971)

Associated with overdrinking of hypotonic fluids and/or excessive salt loss

Athletes at higher risk: women and older adults, smaller athletes who run slowly, sweat less and drink hypotonic fluids before, during and after the race; CF gene carriers; football and tennis players who overhydrate to prevent cramps or get hypotonic IV hydration

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Exercise-Associated

Hyponatremia

Beware of diagnosing the endurance athlete with

dehydration and encouraging hypotonic fluid

replacement

Symptoms occur with rapid decline in levels

below 130 mmol/L

Symptoms increase with the rapidity of decline,

the longer it remains low and the lower it goes

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Exercise-Associated

Hyponatremia

Symptoms at levels of 125 mmol/L or less:

headache, vomiting, swollen hands and feet,

restlessness, fatigue, confusion and

disorientation (cerebral edema), wheezing

(pulmonary edema)

Progression of symptoms with levels below

120mmol/L: cerebral edema with seizure, coma,

brainstem herniation, respiratory arrest and

death

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Exercise-Associated

Hyponatremia

Treatment:

Get a sodium level immediately!

Hypertonic fluid replacement immediately and

transport to the ED with clear diagnosis

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Fluid Replacement – Pre-Exercise

Goal is to start euhydrated

If not euhydrated from prior exercise (<12 hour

interval between activities), drink slowly at least

4 hours prior to exercise

If urine is dark or no urine output, drink more 2

hours prior to exercise

Add salt to beverages or eat salty food to assist

in fluid retention

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Fluid Replacement – During

Exercise

Goal is to prevent excessive dehydration (>2% BW)

Fluid replacement should mirror losses (0.4 - 1.8 L/hr)

and not be excessive, especially in exercise >3 hours

Periodically drink, don’t drink at every water station

Marathoners safe to drink 0.4 – 0.8 L/hr

Slower, thinner athletes most at risk of overhydration in

activity >3 hours

Salty sweaters need to replace electrolytes during

exercise to avoid hyponatremia

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Marathon Hydration Levels and

Body Weight Loss

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Fluid Replacement – After Exercise

Goal is to fully replace fluid and electrolyte deficits

If mild deficits, normal eating and drinking will replace losses with time (12+ hours)

If more moderate deficits, more aggressive replacement is warranted 1.5 L fluid/kg weight lost

Replacing fluid without sodium leads to excessive urine production and delayed euhydration

IVF should be used only when losses exceed >7% BW with inability to ingest oral fluids No benefit vs. oral rehydration

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Sports Drinks

Institute of Medicine-recommended composition of sports drinks for prolonged physical activity in hot weather:

20-30 mEq/L sodium

2-5 mEq/L potassium

5-10% carb Concentrations >8% delay gastric emptying

Ranges are variable to account for different exercise conditions, durations and intensity

Carb intake is important only for extended periods of exercise (>1 hour)

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1mEq Na = 23 mg, 1mEq K = 39 mg

Sports Drinks

8 oz ≈ ¼ L goal is 115-173 mg Na and 20-48 mg K per 8 oz

Gatorlytes add 700 mg Na and 200 mg K; also 70 mg Ca and 40 mg Mg –

only really want to use in salty sweaters or bad crampers.

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Caffeine and Alcohol

Caffeine, in small amounts (< 180 mg/d), does

not lead to dehydration

Alcohol does increase urine output, especially in

higher doses, use in the rehydration period can

delay full rehydration

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Caffeine Content

Red Bull 80 mg/8.3 oz Fixx Extreme Ultra Shot 400mg/0.17 oz

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Summary

Proper hydration is important to good performance

Dehydration negatively impacts performance

Rehydration should be performed orally when possible

Salty sweaters are at risk of hyponatremia if not replacing electrolyte losses

Sports drinks are a good way of replacing losses, but often don’t contain the recommended electrolyte concentrations