Hyponatremia is associated with higher NT-proBNP than normonatremia after prolonged exercise

Effects of Sodium Intake on Health and Performance in Endurance and Ultra-Endurance Sports

The majority of reviews on sports nutrition issues focus on macronutrients, often omitting or paying less attention to substances such as sodium. Through the literature, it is clear that there are no reviews that focus entirely on the effects of sodium and in particular on endurance sports. Sodium intake, both at high and low doses, has been found to be associated with health and performance issues in athletes. Besides, there have been theories that an electrolyte imbalance, specifically sodium, contributes to the development of muscle cramps (EAMC) and hyponatremia (EAH). For this reason, it is necessary to create this systematic review, in order to report extensively on the role of sodium consumption in the population and more specifically in endurance and ultra-endurance athletes, the relationship between the amount consumed and the occurrence of pathological disorders, the usefulness of simultaneous hydration and whether a disturbance of this substance leads to EAH and EAMC. As a method of data collection, this study focused on exploring literature from 2000–2021. The search was conducted through the research engines PubMed and Scopus. In order to reduce the health and performance effects in endurance athletes, simultaneous emphasis should be placed on both sodium and fluid intake.

Exercise-Induced Hyponatremia: An Assessment of the International Hydration Recommendations Followed During the Gran Trail De Peñalara and Vitoria-Gasteiz Ironman Competitions

Introduction

Hyponatremia often occurs during the practice of endurance sports. We evaluated the impact on hyponatremia of the hydration recommendations of the Third International Exercise-Associated Hyponatremia Consensus Development Conference 2015 (3IE-AHCD) during the 2017 Gran Trail de Peñalara marathon (GTP) and the Vitoria Gasteiz Ironman triathlon (VGI).

Methods

Prospective study of GTP and VGI athletes participating in four information sessions in the months prior to the events, to explain that hydration should only be according to their level of thirst, per the recommendations of the 3IE-AHCD. Consenting event finishers were included in final analysis. Pre- and post-race anthropometric and biochemical parameters were compared.

Results

Thirty-six GTP (33 male) and 94 VGI (88 male) finishers were evaluated. GTP race median fluid intake was 800 ml/h, with 900 ml/h in the VGI race. 83.3% GTPfin and 77.6% VGIfin remained eunatremic (blood sodium 135–145 mmol/L). Only 1/36 GTP and 1/94 VGI participant finished in hyponatremia, both with a sodium level of 134 mmol/L. Fourteen percent of GTP, and 21.2% of VGI participants finished in hypernatremia, with no increase in race completion times. No participating athlete required medical attention, except for musculoskeletal complaints. Pro-BNP and Copeptin levels rose significantly. Changes in copeptin levels did not correlate with changes in plasma osmolality, nor total body water content in impedance analysis.

Conclusions

Recommending that athletes' fluid intake in endurance events be a function of their thirst almost entirely prevented development of hyponatremia, without induction of clinically significant hypernatremia, or a negative repercussion on race completion times.

Exercise-Associated Hyponatremia in Endurance and Ultra-Endurance Performance-Aspects of Sex, Race Location, Ambient Temperature, Sports Discipline, and Length of Performance: A Narrative Review

Exercise-associated hyponatremia (EAH) is defined as a plasma sodium concentration of <135 mmol/L during or after endurance and ultra-endurance performance and was first described by Timothy Noakes when observed in ultra-marathoners competing in the Comrades Marathon in South Africa in the mid-1980s. It is well-established that a decrease in plasma sodium concentration <135 mmol/L occurs with excessive fluid intake. Clinically, a mild hyponatremia will lead to no or very unspecific symptoms. A pronounced hyponatremia (<120 mmol/L) will lead to central nervous symptoms due to cerebral edema, and respiratory failure can lead to death when plasma sodium concentration reaches values of <110-115 mmol/L. The objective of this narrative review is to present new findings about the aspects of sex, race location, sports discipline, and length of performance. The prevalence of EAH depends on the duration of an endurance performance (i.e., low in marathon running, high to very high in ultra-marathon running), the sports discipline (i.e., rather rare in cycling, more frequent in running and triathlon, and very frequent in swimming), sex (i.e., increased in women with several reported deaths), the ambient temperature (i.e., very high in hot temperatures) and the country where competition takes place (i.e., very common in the USA, very little in Europe, practically never in Africa, Asia, and Oceania). A possible explanation for the increased prevalence of EAH in women could be the so-called Varon-Ayus syndrome with severe hyponatremia, lung and cerebral edema, which was first observed in marathon runners. Regarding the race location, races in Europe seemed to be held under rather moderate conditions whereas races held in the USA were often performed under thermally stressing conditions (i.e., greater heat or greater cold).

[Exercise-Associated Hyponatremia in Endurance Performance]

Exercise-Associated Hyponatremia in Endurance Performance Abstract. Exercise-associated hyponatremia is defined as a plasma sodium concentration of <135 mmol/l and was first described by Timothy Noakes at the Comrades Marathon in South Africa in the mid-1980s. A decrease in plasma sodium <135 mmol/l occurs with excessive fluid intake. Risk factors include long to very long endurance performance, extreme climatic conditions, female gender and competitions in the USA. Regarding its prevalence by sport, exercise-associated hyponatraemia tends to occur while swimming and running, but rarely when cycling. While mild exercise-associated hyponatremia does not lead to clinical symptoms, severe hyponatremia due to cerebral edema can lead to neurological deficits and even death. The best prevention of exercise-associated hyponatremia is the reduction of fluid intake during exercise.

Proper Hydration During Ultra-endurance Activities

The health and performance of ultra-endurance athletes is dependent on avoidance of performance limiting hypohydration while also avoiding the potentially fatal consequences of exercise-associated hyponatremia due to overhydration. In this work, key factors related to maintaining proper hydration during ultra-endurance activities are discussed. In general, proper hydration need not be complicated and has been well demonstrated to be achieved by simply drinking to thirst and consuming a typical race diet during ultra-endurance events without need for supplemental sodium. As body mass is lost from oxidation of stored fuel, and water supporting the intravascular volume is generated from endogenous fuel oxidation and released with glycogen oxidation, the commonly promoted hydration guidelines of avoiding body mass losses of >2% can result in overhydration during ultra-endurance activities. Thus, some body mass loss should occur during prolonged exercise, and appropriate hydration can be maintained by drinking to the dictates of thirst.

Management of Suspected Fluid Balance Issues in Participants of Wilderness Endurance Events

Dehydration and exercise-associated hyponatremia (EAH) are both relatively common conditions during wilderness endurance events. Whereas dehydration is treated with fluids, EAH is appropriately managed with fluid restriction and a sodium bolus but can worsen with isotonic or hypotonic fluids. Therefore, caution is recommended in the provision of postevent rehydration in environments where EAH is a potential consideration because accurate field assessment of hydration status can be challenging, and measurement of blood sodium concentration is rarely possible in the wilderness. Dehydration management with oral rehydration is generally adequate and preferred to intravenous rehydration, which should be reserved for athletes with sustained orthostasis or inability to tolerate oral fluid ingestion after some rest. In situations where intravenous hydration is initiated without known blood sodium concentration or hydration status, an intravenous concentrated sodium solution should be available in the event of acute neurological deterioration consistent with the development of EAH encephalopathy.

Are we being drowned by overhydration advice on the Internet?

OBJECTIVE

Because inappropriate recommendations about hydration during exercise appear widespread and potentially dangerous, we assessed the quality of a sampling of information currently available to the public on the Internet.

METHODS

Internet searches using the Google search engine were conducted using the terms "hydration," "hydration guidelines," "drinking fluids" and "drinking guidelines" combined with "and exercise." From the first 50 websites for each search phrase, duplicates were removed yielding 141 unique websites that were categorized by source and examined for specific hydration related information and recommendations.

RESULTS

Correct endorsement was as follows (reported as percent endorsing the concept relative to the number of websites addressing the issue): some weight loss should be expected during exercise (69.5% of 95), fluid consumption during exercise should be based upon thirst (7.3% of 110), electrolyte intake is not generally necessary during exercise (10.4% of 106), dehydration is not generally a cause of heat illness (3.4% of 58) or exercise-associated muscle cramping (2.4% of 42), exercise-associated muscle cramping is not generally related to electrolyte loss (0.0% of 16), and overhydration is a risk for hyponatremia (100.0% of 61). Comparison of website information from medical or scientific sources with that from other sources revealed no differences (p = 0.4 to 1.0) in the frequency of correct endorsement of the examined criteria.

CONCLUSION

Prevalent misinformation on the Internet about hydration needs during exercise and the contribution of hydration status to the development of heat illness and muscle cramping fosters overhydration. In general, those websites that should be most trusted by the public were no better than other websites at providing accurate information, and the potential risk of hyponatremia from overhydration was noted by less than half the websites. Since deaths from exercise-associated hyponatremia should be preventable through avoidance of overhydration, dissemination of a more appropriate hydration message is important.

Sodium Supplementation and Exercise-Associated Hyponatremia during Prolonged Exercise

PURPOSE

This work examines whether sodium supplementation is important in prevention of hyponatremia during continuous exercise up to 30 h and whether any distinguishing characteristics of those developing hyponatremia could be identified.

METHODS

Participants of the 161-km Western States Endurance Run underwent body weight measurements before, during, and after the race, completed a postrace questionnaire about drinking strategies and use of sodium supplementation during four race segments, and underwent analysis of postrace serum sodium concentration.

RESULTS

The postrace questionnaire was completed by 74.5% of the 376 starters, a postrace blood sample was provided by 61.1% of the 296 finishers, and 53.0% of finishers completed the postrace survey and also provided a postrace blood sample. Among this population, the incidence of hyponatremia among finishers was 6.6% and sodium supplements were used by 93.9% of the runners. Postrace serum sodium concentration was found to be directly related to the rate of sodium intake in supplements (r = 0.24, P = 0.0027) and indirectly related to the percentage change in body weight from immediately before the race start (r = -0.19, P = 0.010). There was no difference in rate of sodium intake in supplements between the hyponatremic and normonatremic finishers, and none of the hyponatremic finishers lost >4.3% body weight. Hyponatremic finishers were not distinguished from normonatremic or hypernatremic finishers by other runner characteristics considered, drinking strategies, or gastrointestinal symptoms of nausea and vomiting.

CONCLUSIONS

We conclude that a low sodium intake in supplements has minimal responsibility for development of hyponatremia during continuous exercise up to 30 h, whereas overhydration is the primary characteristic of those developing hyponatremia. Therefore, avoiding overhydration seems to be the most important means for preventing hyponatremia under these conditions.

Wilderness Medical Society practice guidelines for treatment of exercise-associated hyponatremia: 2014 update

Exercise-associated hyponatremia (EAH) is defined by a serum or plasma sodium concentration below the normal reference range of 135 mmol/L that occurs during or up to 24 hours after prolonged physical activity. It is reported to occur in individual physical activities or during organized endurance events conducted in austere environments in which medical care is limited and often not available, and patient evacuation to definitive care is often greatly delayed. Rapid recognition and appropriate treatment are essential in the severe form to ensure a positive outcome. Failure in this regard is a recognized cause of event-related fatality. In an effort to produce best practice guidelines for EAH in the austere environment, the Wilderness Medical Society convened an expert panel. The panel was charged with the development of evidence-based guidelines for management of EAH. Recommendations are made regarding the situations when sodium concentration can be assessed in the field and when these values are not known. These recommendations are graded on the basis of the quality of supporting evidence and balance between the benefits and risks/burdens for each parameter according to the methodology stipulated by the American College of Chest Physicians. This is an updated version of the original WMS Practice Guidelines for Treatment of Exercise-Associated Hyponatremia published in Wilderness & Environmental Medicine 2013;24(3):228-240.

Hiker Fatality From Severe Hyponatremia in Grand Canyon National Park

We present the case of a hiker who died of severe hyponatremia at Grand Canyon National Park. The woman collapsed on the rim shortly after finishing a 5-hour hike into the Canyon during which she was reported to have consumed large quantities of water. First responders transported her to the nearest hospital. En route, she became unresponsive, and subsequent treatment included intravenous normal saline. Imaging and laboratory data at the hospital confirmed hypervolemic hyponatremia with encephalopathy. She never regained consciousness and died of severe cerebral edema less than 24 hours later. We believe this is the first report of a fatality due to acute hyponatremia associated with hiking in a wilderness setting. This case demonstrates the typical pathophysiology, which includes overconsumption of fluids, and demonstrates the challenges of diagnosis and the importance of appropriate acute management. Current treatment guidelines indicate that symptomatic exercise-associated hyponatremia should be acutely managed with hypertonic saline and can be done so without concern over central pontine myelinolysis, whereas treatment with high volumes of isotonic fluids may delay recovery and has even resulted in deaths.

Three cases of severe hyponatremia during a river run in Grand Canyon National Park

We present 3 cases of severe hyponatremia occurring on a commercially guided river rafting trip on the Colorado River in Grand Canyon National Park. All 3 women appeared to have been overhydrating because of concern about dehydration and required evacuation within 24 hours of each other after the staggered onset of symptoms, which included fatigue and emesis progressing to disorientation or seizure. Each was initially transferred to the nearest hospital and ultimately required intensive care. Imaging and laboratory data indicated all 3 patients had hypervolemic hyponatremia. Unlike the well-documented exercise-associated hyponatremia cases commonly occurring in prolonged endurance athletic events, these 3 unique cases of acute hyponatremia were not associated with significant exercise. The cases illustrate the diagnostic and treatment challenges related to acute hyponatremia in an austere setting, and underscore the importance of preventive measures focused on avoidance of overhydration out of concern for dehydration.

Physiopathological, Epidemiological, Clinical and Therapeutic Aspects of Exercise-Associated Hyponatremia

Exercise-associated hyponatremia (EAH) is dilutional hyponatremia, a variant of inappropriate antidiuretic hormone secretion (SIADH), characterized by a plasma concentration of sodium lower than 135 mEq/L. The prevalence of EAH is common in endurance (<6 hours) and ultra-endurance events (>6 hours in duration), in which both athletes and medical providers need to be aware of risk factors, symptom presentation, and management. The development of EAH is a combination of excessive water intake, inadequate suppression of the secretion of the antidiuretic hormone (ADH) (due to non osmotic stimuli), long race duration, and very high or very low ambient temperatures. Additional risk factors include female gender, slower race times, and use of nonsteroidal anti-inflammatory drugs. Signs and symptoms of EAH include nausea, vomiting, confusion, headache and seizures; it may result in severe clinical conditions associated with pulmonary and cerebral edema, respiratory failure and death. A rapid diagnosis and appropriate treatment with a hypertonic saline solution is essential in the severe form to ensure a positive outcome.

Exercise-associated hyponatremia and hydration status in 161-km ultramarathoners

PURPOSE

This work combines and reanalyzes 5 yr of exercise-associated hyponatremia (EAH) research at 161-km ultramarathons in northern California with primary purposes to define the relationship between postrace blood sodium concentration ([Na]) and change in body weight; to examine the interactions among EAH incidence, ambient temperature, and hydration state; and to explore the effect of hydration status on performance.

METHODS

Prerace and postrace body weight and finish time data were obtained on 887 finishers, and postrace [Na] was also obtained on a subset of 669 finishers.

RESULTS

EAH incidence was 15.1% overall (range, 4.6%-51.0% by year) and had a significant positive relationship with ambient temperature. Of the runners with EAH, 23.8% were classified as overhydrated (weight change, ≥0), 40.6% were euhydrated (weight change, <0% to -3%), and 35.6% were dehydrated (weight change, <-3%) at the finish. There was a weak significant relationship (r = 0.17, P < 0.0001) between postrace [Na] and change in body weight such that a lower [Na] was more common with increased weight loss. Considering all finishers examined, 18.5% were dehydrated and 34.9% were overhydrated at the finish. There was a weak significant relationship (r = 0.092, P = 0.006) between change in body weight and performance in that faster runners tended to lose more weight. Top finishers varied in body weight change from ∼1% gain to ∼6% loss.

CONCLUSIONS

EAH incidence can be high in 161-km ultramarathons in northern California. In this environment, EAH is more common with dehydration than overhydration and is more common in hotter ambient temperature conditions. Because weight loss >3% does not seem to have an adverse effect on performance, excessive sodium supplementation and aggressive fluid ingestion beyond the dictates of thirst are ill advised.