A study of serum sodium level among Hong Kong runners

Exercise-Associated Hyponatremia in Marathon Runners

Exercise-associated hyponatremia (EAH) was first described as water intoxication by Noakes et al. in 1985 and has become an important topic linked to several pathological conditions. However, despite progressive research, neurological disorders and even deaths due to hyponatremic encephalopathy continue to occur. Therefore, and due to the growing popularity of exercise-associated hyponatremia, this topic is of great importance for marathon runners and all professionals involved in runners' training (e.g., coaches, medical staff, nutritionists, and trainers). The present narrative review sought to evaluate the prevalence of EAH among marathon runners and to identify associated etiological and risk factors. Furthermore, the aim was to derive preventive and therapeutic action plans for marathon runners based on current evidence. The search was conducted on PubMed, Scopus and Google Scholar using a predefined search algorithm by aggregating multiple terms (marathon run; exercise; sport; EAH; electrolyte disorder; fluid balance; dehydration; sodium concentration; hyponatremia). By this criterion, 135 articles were considered for the present study. Our results revealed that a complex interaction of different factors could cause EAH, which can be differentiated into event-related (high temperatures) and person-related (female sex) risk factors. There is variation in the reported prevalence of EAH, and two major studies indicated an incidence ranging from 7 to 15% for symptomatic and asymptomatic EAH. Athletes and coaches must be aware of EAH and its related problems and take appropriate measures for both training and competition. Coaches need to educate their athletes about the early symptoms of EAH to intervene at the earliest possible stage. In addition, individual hydration strategies need to be developed for the daily training routine, ideally in regard to sweat rate and salt losses via sweat. Future studies need to investigate the correlation between the risk factors of EAH and specific subgroups of marathon runners.

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.

Subclinical hypernatraemia in a population of endurance racing sled dogs

Electrolyte disturbances occur in both human and veterinary endurance athletes; however, hypernatraemia is poorly documented in dogs. To further explore electrolyte changes in canine endurance athletes, we collected blood from two teams of dogs (n=16) participating in the mid-distance (336 km) CanAm race. Serum samples were collected 36 hours before the start and within 20 minutes of race completion. Serum was similarly collected from 18 dogs withdrawn after completing 264 km. Biochemical profiles and aldosterone assays were performed. Mean serum sodium (>155 mEq/l) and corrected chloride concentrations were significantly increased (P<0.01) from baseline in finishing and withdrawn dogs; however, unlike sodium, corrected chloride concentrations remained within the reference interval. Serum phosphorous, hepatic enzymes, cholesterol, creatinine kinase, blood urea nitrogen, globulin, glucose, and iron concentrations were also significantly increased (P<0.01) compared to baseline in both finishing and withdrawn dogs. Both mean serum aldosterone and urea nitrogen concentrations were significantly increased (P<0.01) from baseline in finishing and withdrawn dogs, with finishers having greater concentrations than withdrawn dogs (P<0.01). Pre-race and matched finishing dog populations were then used for correlation analysis. Serum sodium concentrations were significantly (P<0.01) and strongly correlated with chloride (r=0.92), albumin (r=0.88), total protein (r=0.87), globulin (r=0.81), and potassium (r=0.86). Serum sodium concentrations were not significantly correlated with serum aldosterone concentrations (r=0.04, P=0.87). This study uniquely described subclinical hypernatraemia in the canine endurance athlete. The data lend support of dehydration through free water loss as a cause of hypernatraemia likely compounded by insufficient replenishment by drinking. Elevations in aldosterone concentrations in the face of hypernatraemia may be attributed to concurrent extra-renal hypotonic water losses, counter regulatory hormone influences, or physiological hyperthermia. Such findings demonstrate a degree of clinical tolerance for euvolemic driven hypernatraemia in endurance sled dogs, while highlighting the need for appropriate water supplementation.

Dysnatremia among runners in a half marathon performed under warm and humid conditions

Background

Dysnatremia has been associated with sports activity, especially long-distance running and endurance sports. High fluid intake is associated with hyponatremia. This study aims to evaluate dysnatremia and risk factors in half-marathon runners under warm and humid environmental conditions.

Methods

A cross-sectional study was performed among randomly selected runners in the 2017 Cali half marathon. Runners on diuretic therapy or with a known history of kidney disease were excluded. Participants went through a 2-day assessment. Previous medical history, training history, body mass index and running history were determined in the first assessment. Symptoms of dysnatremia and level of fluid consumption during the race were registered during the second assessment and post-run blood sampling for serum [Na+] was also undertaken.

Results

130 runners were included in the study. The complete 2-day assessment was performed on 81 participants (62%) that were included in the final analysis. No cases of hyponatremia were found; instead, there were six cases of asymptomatic hypernatremia (7.4%). This hypernatremia had a statistically significant association with lower frequency (p=0.01) and volume of fluid intake during the race (water: p=0.02, Gatorade: p=0.04).

Conclusion

Hyponatremia has been associated with high fluid intake in races performed under cool weather, such as the Boston Marathon during spring. In contrast, hypernatremia was found in a half marathon in warm and humid weather, which was associated with lower volume and frequency of fluid intake, suggesting that under warm and humid conditions, a median fluid intake of 900 mL during the race could prevent this event.

Exercise-Associated Hyponatremia: 2017 Update

Exercise-associated hyponatremia (EAH) was initially described in the 1980s in endurance athletes, and work done since then has conclusively identified that overdrinking beyond thirst and non-osmotic arginine vasopressin release are the most common etiologic factors. In recent years, EAH has been described in a broader variety of athletic events and also has been linked to the development of rhabdomyolysis. The potential role of volume and sodium depletion in a subset of athletes has also been described. This review focuses on the most recent literature in the field of EAH and summarizes key new findings in the epidemiology, pathophysiology, treatment, and prevention of this condition.