Exercise-Associated Hyponatremia,

Hyperthermia, and the Balance of Fluids

Andrew Getzin, MDClinical DirectorCayuga Medical CenterSports Medicine and Athletic Performancewww.cayugamed.org/sportsmedicine

Objectives

• Understand how to diagnose and treat exercise-associated hyponatremia

• Understand the best means for lowering core body temperature in a hyperthermic athlete

• Gain an improved understanding of individual fluid needs for endurance athletes

Question 1: What is the correct treatment for minimally symptomatic exercise-induced hyponatremia?A. Administering NS at 200cc/hour for 24 hoursB. Hypertonic (3%) saline intravenous 100mL

bolusC. Wait for the individual to voidD. Lasix 80mg

Question 2: What is the best way to lower core body temperature in a athlete with heat stroke?

A. Cooling fansB. Ice water immersion at 2°CC. Warm water immersion at 26°CD. Eating lots of ice cream

Question 3: What is the ideal fluid consumption rate for a heat acclimatized 77Kg male competing in an international distance triathlon who is an above average sweater on a 61 degree day with 87% humidity and minimal wind?

A. He should not consume any fluidsB. 200ml per hourC. 600ml per hourD. 1L per hour

“I am of the opinion that in the healthy subject the only potential

risk to life is heat stroke… a danger well exhibited by

examples I have seen of alarming collapse and, on one occasion,

death.”Sir Adolphe Abrahams, article on athletics, Encyclopaedia of Medical Practice, 1950

Sawka, MSSE 1992

Hypohydration Effects on Aerobic Power

Sawka, MSSE 1992

The Danger of an Inadequate Water Intake in Marathon Running

• Wyndham and Strydom, 1969, SA Medical Journal

• Sugar’s marathon x 2 in 1968• 20 volunteers• Increase rectal temperatures when 3% water

deficit

“The ideal regimen of water drinking is to take about 300ml every 20 minutes or so. This should start right at the beginning of the race.”

1996 ACSM Position Stand: Exercise and Fluid Replacement

• Drink adequate fluids 24 hours before the event

• Drink 500ml of fluids 2 hours before exercise• During exercise, athletes should start drinking

early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all the water lost through sweating (i.e., body weight loss), or consume the maximal amount that can be tolerated.

Team in Training Newsletter 2010

When you are training alone be sure to either carry fluids, stash them along your route or plan to run routes that will take you by places where you can stop at regular intervals for a drink. At group training sessions all runners must stop and drink at every water stop! It is essential that you drink plenty of fluids to stay well hydrated. Thirst is a sign that you’re already dehydrated. Drink before you get thirsty!

EAH is the occurrence of hyponatremia during or up to 24 hours after prolonged physical activity and is defined by a serum or plasma sodium concentration below the normal reference range of the laboratory performing the test. For most laboratories, this is a [Na+] < 135 mmol/L

Exercise Associated Hyponatremia (EAH)

EAH is primarily adilutional hyponatremia

caused by an increase in totalbody water relative to the amount

of total exchangeable Na+

The primary etiological factor inmost cases appears to bethe consumption of fluids

in excess of body fluid losses

Weight Gain with EAH

• In most reported cases of symptomatic EAH there is bodyweight gain suggestive of an absolute increase in total body water

• Body weight loss is expected due to oxidation of substrate

• A dilutational hyponatremia may still occur with loss of body weight- Lebus CJSM 2010

Arginine Vasopressin (AVP)

0 250 500 750 10000

200

400

600

800

1000

Urine volume (ml/h)

1

296

294

292

290

288

286

284

282

280

278

plasmaOsmolality

plasmaAVP

(pg/ml)

urineosmolality

(mOsm/kg H2O)thirst

osmoticthreshold

AVPosmotic

threshold

2

3

4

5

6

7

8

9

0

maximal urine

excretion rate (ml/h)

1000500

250

Verbalis JG, Best Practice and Research Clin Endocrinology and Metabolism 2003

Potential Non-Osmotic Stimuli of AVP During Exercise

• Endocrine factors, Hew-Butler

• Nausea and Vomiting, Rowe

• Hypoglycemia, Verbalis

• Cytokines, Siegel

• Elevated body temperature, Takamata

Hew-Butler, 2010 Br J Sports Med

Which Athletes Have Inappropriate AVP Release?

• 13% of marathon runners, Almond NEJM 2005

• 27% of Ironman triathletes, Speedy Clin J Sport Med 1997

• 5% of cyclists in a 109-km cycle race, Hew-Butler, Br J Sports Med 2010

Athlete Related Risk Factors for EAH

• Excessive drinking• Weight gain• Low body weight• Female sex• Slow running• Event inexperience• NSAIDs

Hew, Clin J Sports Med 2003

Event Related Risk Factors for EAH

• High fluid availability

• > 4 hours of exercise

• Unusually hot conditions

• Extreme cold

Excessive sodium loss has not yet been demonstratedto be a causative factor in the pathogenesis of EAH

Sodium loss has been shown to be no greater in individuals who develop EAH

than in individuals who do not

Sodium Loss and EAH

Ingestion of Electrolyte Drinks Can Not Prevent EAH

• All drinks have sodium concentration of <125 mmol/L

• The ingestion of sodium will be excreted in the urine rather than retained in the body of inappropriate AVP is released

EAH Early Signs and Symptoms

• Bloating

• Puffiness

• Headache

• Nausea/Vomiting

Statement of 2nd International EAH Conference, New Zealand 2007. Clin J Sports Med 2008

EAH Late Signs and Symptoms

• Altered mental status

• Seizures

• Respiratory distress

• Coma

• Death

Ayus, Ann Intern Med 2000

Hyponatremia Post Treatment

Treatment of Minimally Symptomatic EAH

• Restrict fluid intake until the onset of urination

• Seek medical attention if symptoms worsen

• IV isotonic or hypertonic fluid administration is not usually necessary

Treatment of Severely Symptomatic EAH

• Administer a bolus infusion of 100ml 3% NaCl

• Up to 2 additional boluses of 100ml of 3% NaCl may be given at 10 minute intervals if no clinical improvement

• This regimen should not pose any substantial danger to the patient

• Stabilize, transport immediately, communicate with ER

Hew Butler, Clin J Sport Med 2008

Symptomatic EAH Treatment

Avoid the administration of isotonic or hypotonic fluids to prevent worsening the degree of hyponatremia and fluid overload

Chicago Marathon 2007

• October 2007, 31° C (88°F)

• 35 year old male police officer died from heat stroke

• 300 hospitalizations• Canceled the marathon

half way into it

Mechanism of Heat Transfer• Conduction: transfer of heat

from warmer to cooler objects– Direct Contact– Water 32x > air

• Convection: movement of heat away from body by the movement of ambient air

• Radiation: heat transfer by electromagnetic waves

• Evaporation: conversion of liquid to gas– Greatest means of cooling

when running– For every 1.7 ml of sweat

evaporated, 1kcal of heat is dissipated

Thermoregulation with Heat StressEnvironmental Heat Load Metabolic Heat Load

(Exercise)

Body heat

Core temperature

Sweating

Heat loss by evaporation

Cutaneous vasodilatation

Heat loss by radiationfrom skin surface

Acclimatization

• Increase aerobic capacity– Increased number of mitochondria/cell– Increased muscle glycogen stores– Training at intensity of 50% VO2max provides for ½

acclimatization needs• Increased sweating capacity

– Lower temperature threshold for vasodilation– Increased volume

• Increased Aldosterone production– 10-25% increase in plasma volume– Lower sweat sodium concentration

Spectrum of Heat Illness

• Heat cramps• Heat edema• Heat exhaustion• Heat stroke

Heat Exhaustion• Dehydration, electrolyte loss, core temperature

normal or slightly elevated• Symptoms: orthostatic vital signs, dyspnea,

weakness, profuse sweating, nausea/vomiting, irritability, headache, absence of serious central nervous system dysfunction

• Treatment: moderate cooling, remove to cool environment, remove excess clothing, fans, cool water, IV fluid if necessary

• Commonly occurs

Heat Stroke

• Core temperature>40°C (104°F) + CNS dysfunction

• Symptoms: hypotension, vomiting, diarrhea, mental status change, seizures, coma

• Lab abnormalities: increased LFTs, increased CPK, proteinurea, granular casts, hematuria, myoglobinuria

• Poor prognosis: temp >42°C (107.6), aspartate transaminase >1000 first 24 hours

Seizures Exercise K+ Ambient temp Prolonged sweating

Anticholinergicmeds

Muscularhyperactivity

Vasodilatation Fluid losses

Sweatingceases

AcidosisRhabdomyolysi

s

Muscle perfusionShock

Furthercore temp

Myocardial injury

DIC

CNS damageAcute renal

failure

Myoglo-binuria

K+

Arrhythmias

Heat Stroke - Multisystem Sequelae

Heat Stroke Diagnosis

• Valid temperature: ideally core temperature via rectal

• CNS dysfunction: coma, altered consciousness, irrational behavior, confusion, convulsions, disorientation, irritability, apathy, hysteria

Lawrence, et al, Exertional Heat Illness During Training and Competition, MSSE 2007

Treatment

Water Immersion

• Have tub prepared in advance

• Temperature between 2°C (35.6°F) and 26°C (78.8°F)?

• Pull out at about 38° (100.4°F)

• Monitor athlete closely• Transport second

Proulx, et al, J Appl Phys 2002

Hyperthermia Prevention

What Is the Correct Amount Of Fluid?

• Dehydration increases the risk for hyperthermia.• Overhydration can cause EAH.• It is OK to drink as thirst dictates.• Approximately 400-800ml (1 large water bottle)

per hour• Less fluid for slower, smaller athletes exercising

in mild environment• Be conditioned to environment.• Practice drinking in your training.• LISTEN TO YOUR BODY!!!

Noakes, IMMDA-AIMS Advisory statement on guidelines for fluid replacement during marathon running, Clin J Sports Med 2003

Prevention

• Drink to thirst

• Monitor body weight

• If you feel your temperature rising, slow down!

Hyperthermia vs. Hyponatremia

• If they make it to the finish line- statistics are positive

• What is the temperature?• What is the distance of the race?• Who are you evaluating?• Exam including a rectal temp, ?sodium level

Thank You