Hyponatremia Associated with Overhydration in U.S. Army Trainees

O'Brien, Karen; Montain, Scott J.; Corr, William P.; Sawka, Michael N.; Knapik, Joseph J.; Craig, Stephen C.

doi:10.1093/milmed/166.5.405

Cited by 76 publications

(57 citation statements)

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“…Many of these reports relate to a series of fatalities in the military between 1989 and 1996 (27)(28)(29). During this period, military recruits were encouraged to ingest 1.8 L of fluid for every hour they were exposed to temperatures above 30°C (30).…”

Section: Incidencementioning

confidence: 99%

Exercise-Associated Hyponatremia

Rosner

Kirven

2007

Clinical Journal of the American Society of Nephrology

170

165

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Exercise-associated hyponatremia has been described after sustained physical exertion during marathons, triathlons, and other endurance athletic events. As these events have become more popular, the incidence of serious hyponatremia has increased and associated fatalities have occurred. The pathogenesis of this condition remains incompletely understood but largely depends on excessive water intake. Furthermore, hormonal (especially abnormalities in arginine vasopressin secretion) and renal abnormalities in water handling that predispose individuals to the development of severe, life-threatening hyponatremia may be present. This review focuses on the epidemiology, pathogenesis, and therapy of exercise-associated hyponatremia.

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Section: Incidencementioning

confidence: 99%

Exercise-Associated Hyponatremia

Rosner

Kirven

2007

Clinical Journal of the American Society of Nephrology

170

165

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“…A striking example of this imbalance is seen when a low serum sodium concentration (hyponatraemia below 130 mmol × l 71 ) causes fluid movement into the brain, causing swelling with symptoms that can progress from feeling strange, to mental confusion, general weakness, collapse, seizure, coma and death. Because the sodium concentration in sweat is much lower than that of plasma, the primary cause of hyponatraemia is dilution of body water by drinking a large volume of low sodium-containing fluid over several hours, and it can be exacerbated by also losing large amounts of sodium in sweat (Vrijens and Rehrer, 1999;Montain et al, 2001;O'Brien et al, 2001;Rehrer, 2001).…”

Section: Salt Intake During Exercisementioning

confidence: 99%

Fluid and fuel intake during exercise

Coyle¹

2004

Journal of Sports Sciences

330

205

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The amounts of water, carbohydrate and salt that athletes are advised to ingest during exercise are based upon their effectiveness in attenuating both fatigue as well as illness due to hyperthermia, dehydration or hyperhydration. When possible, fluid should be ingested at rates that most closely match sweating rate. When that is not possible or practical or sufficiently ergogenic, some athletes might tolerate body water losses amounting to 2% of body weight without significant risk to physical well-being or performance when the environment is cold (e.g. 5-108C) or temperate (e.g. 21-228C). However, when exercising in a hot environment ( 4308C), dehydration by 2% of body weight impairs absolute power production and predisposes individuals to heat injury. Fluid should not be ingested at rates in excess of sweating rate and thus body water and weight should not increase during exercise. Fatigue can be reduced by adding carbohydrate to the fluids consumed so that 30-60 g of rapidly absorbed carbohydrate are ingested throughout each hour of an athletic event. Furthermore, sodium should be included in fluids consumed during exercise lasting longer than 2 h or by individuals during any event that stimulates heavy sodium loss (more than 3-4 g of sodium). Athletes do not benefit by ingesting glycerol, amino acids or alleged precursors of neurotransmitter. Ingestion of other substances during exercise, with the possible exception of caffeine, is discouraged. Athletes will benefit the most by tailoring their individual needs for water, carbohydrate and salt to the specific challenges of their sport, especially considering the environment's impact on sweating and heat stress.Keywords: carbohydrate, dehydration, fatigue, gastrointestinal function, hyperthermia, sodium. IntroductionWhen athletes exercise during training or while competing, it is clear that they sometimes benefit by ingesting various mixtures of water, carbohydrate and electrolytes (Convertino et al., 1996;Casa, 2000). The benefits can be expressed through improved performance and/or reduced physiological stress, on an athlete's cardiovascular, central nervous and muscular systems. Although ample scientific evidence exists to support the general theory for encouraging athletes to consume water, carbohydrate and electrolytes during exercise, the practical recommendations for optimally applying these general theories is not simple. This is due to the quite varied nature of the physical stresses encountered during training and competition for a wide range of sports, as well as the unique rules of each sport regarding the allowance for fluid and fuel intake during competition. Furthermore, variations in the physical intensity, duration and environment, as well as individual characteristics of a given athlete, might alter their optimal rate of water, carbohydrate and salt intake as well as the rate of gastrointestinal absorption and feelings of fullness. This task of developing consensus for general recommendations becomes less daunting when approached systematical...

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“…However, dilution of the plasma as reflected in mild, largely asymptomatic hyponatremia is said to be common in general practice (33). Moreover, nonfatal hyponatremia has been reported in a variety of circumstances (32,48,64). In the majority of patients, hyponatremia reflects an excess of water in the body rather than a decrease in sodium (91).…”

Section: Nonfatal Hyponatremiamentioning

confidence: 99%

“Drink at least eight glasses of water a day.” Really? Is there scientific evidence for “8 × 8”?

Valtin¹

2002

American Journal of Physiology-Regulatory, Integrative and Comp

179

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Despite the seemingly ubiquitous admonition to “drink at least eight 8-oz glasses of water a day” (with an accompanying reminder that beverages containing caffeine and alcohol do not count), rigorous proof for this counsel appears to be lacking. This review sought to find the origin of this advice (called “8 × 8” for short) and to examine the scientific evidence, if any, that might support it. The search included not only electronic modes but also a cursory examination of the older literature that is not covered in electronic databases and, most importantly and fruitfully, extensive consultation with several nutritionists who specialize in the field of thirst and drinking fluids. No scientific studies were found in support of 8 × 8. Rather, surveys of food and fluid intake on thousands of adults of both genders, analyses of which have been published in peer-reviewed journals, strongly suggest that such large amounts are not needed because the surveyed persons were presumably healthy and certainly not overtly ill. This conclusion is supported by published studies showing that caffeinated drinks (and, to a lesser extent, mild alcoholic beverages like beer in moderation) may indeed be counted toward the daily total, as well as by the large body of published experiments that attest to the precision and effectiveness of the osmoregulatory system for maintaining water balance. It is to be emphasized that the conclusion is limited to healthy adults in a temperate climate leading a largely sedentaryexistence, precisely the population and conditions that the “at least” in 8 × 8 refers to. Equally to be emphasized, lest the message of this review be misconstrued, is the fact (based on published evidence) that large intakes of fluid, equal to and greater than 8 × 8, are advisable for the treatment or prevention of some diseases and certainly are called for under special circumstances, such as vigorous work and exercise, especially in hot climates. Since it is difficult or impossible to prove a negative—in this instance, the absence of scientific literature supporting the 8 × 8 recommendation—the author invites communications from readers who are aware of pertinent publications.

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Hyponatremia Associated with Overhydration in U.S. Army Trainees

Cited by 76 publications

References 0 publications

Exercise-Associated Hyponatremia

Exercise-Associated Hyponatremia

Fluid and fuel intake during exercise

“Drink at least eight glasses of water a day.” Really? Is there scientific evidence for “8 × 8”?

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