Tamara Hew-Butler

Statement of the Second International Exercise-Associated Hyponatremia Consensus Development Conference, New Zealand, 2007.

Tamara Hew-Butler, DPM, PhD,* J. Carlos Ayus, MD,† Courtney Kipps, BMBS, MSc,‡ Ronald J. Maughan, PhD,§ Samuel Mettler, MSc,¶ Willem H. Meeuwisse, MD, PhD (chair),k Anthony J. Page, MBChB, MD,** Stephen A. Reid, MBBS, PhD,†† Nancy J. Rehrer, PhD,‡‡ William O. Roberts, MD, MSc,§§ Ian R. Rogers, MBBS,¶¶ Mitchell H. Rosner, MD,kk Arthur J. Siegel, MD,*** Dale B. Speedy, MBChB, MD,††† Kristin J. Stuempfle, PhD,‡‡‡ Joseph G. Verbalis, MD,§§§ Louise B. Weschler, MAT, PT,¶¶¶ and Paul Wharam, MMedSckkk

Consensus statement of the 1st International Exercise-Associated Hyponatremia Consensus Development Conference, Cape Town, South Africa 2005.

Over the past decade, exercise-associated hyponatremia (EAH) has emerged as an important complication of prolonged endurance activity. Prior to 1985, this condition was not reported, and runners generally finished marathons with weight loss but without serious medical complications. Abnormalities of serum sodium concentrations ([Na]), when measured, were confined to elevated levels consistent with varying degrees of volume depletion. In March 2005, a panel of twelve international experts on exercise physiology, sport medicine, water metabolism and body fluid homeostasis convened in Cape Town, South Africa, for the 1st International Exercise-Associated Hyponatremia Consensus Development Conference. The primary goal of this panel was to review all of the existing data on EAH and formulate an evidence-based analysis that would define the current understanding of the pathophysiology of EAH. In particular, the panel was constituted to facilitate integration of existing medical and scientific knowledge of other forms of hyponatremia with the occurrence of this homeostatic imbalance during endurance exercise. A secondary goal of the EAH Consensus Development Conference was to prepare a statement that would serve to curtail the growing problem of EAH by disseminating the most current information to both medical personnel and the greater public on the prevalence, nature and treatment of this disorder. The panel strived to clearly articulate what we agreed upon, debate issues that we did not agree upon, and describe in detail what we did and did not know, including minority viewpoints that were supported by clinical and experimental data. The following statement reflects a concise summary of the data deliberated and synthesized by the panel and provides a ‘‘snapshot in time’’ of the current state of knowledge on EAH. New knowledge will continue to advance regarding our understanding of EAH, and will mandate future updates to this consensus statement.

Updated Fluid Recommendation: Position Statement From the International Marathon Medical Directors Association (IMMDA)

Controversy exists regarding optimal fluid guidelines for athletes engaging in different sports. Most published recommendations emphasize the detrimental consequences of dehydration, while more recent reports warn of the morbid consequences of hyperhydration. Accordingly, individualized recommendations emphasizing a balance between the two extremes have evolved. These revised guidelines, however, continue to promote static recommendations for what in reality are very dynamic athletic situations. Marathon running epitomizes a dynamic situation that requires a constant adjustment to constantly changing homeostatic requirements. Real-time assessments of fluid and sodium homeostasis are physiologically represented by changes in plasma osmolality (POsm). Pituitary arginine vasopressin (AVP) secretion is stimulated when POsm increases by only 1% to 2%, representing the body’s attempt to prevent dehydration by decreasing kidney water excretion. After maximal antidiuresis is achieved, thirst is then stimulated to replace water losses that are in excess of the ability of AVP-stimulated antidiuresis to conserve body water. In general, the osmotic threshold for thirst is 5 to 10mOsm/g H2O higher than that of AVP secretion. Thus, thirst is stimulated with decreases in body water of approximately 1.7% to 3.5%. Concomitant performance decrements and cardiovascular strain are also documented when baseline body fluid losses exceed approximately 2%. The failure of athletes to replace 100% of bodyweight losses from ad libitum fluid intake has been well-described as ‘‘involuntary’’ or ‘‘voluntary’’ dehydration; this phenomenon has resulted in the devaluation of thirst as a ‘‘poor’’ indicator of body fluid needs. The combination of laboratory with recent field data (see Table 1 and subsequent discussion), however, suggests that the body primarily defends POsm, and not blood or extracellular fluid volume during prolonged endurance exercise. Because it is well established that thirst is stimulated in response to changes in tonicity in most land mammals, it seems reasonable to conclude that thirst would be the predominant physiologic and dynamic regulator governing fluid balance during exercise. This article will focus on the physiology of normal fluid balance as the ultimate guide toward the evolution of optimal fluid recommendations. Six physiologic considerations of fluid and sodium balance will be detailed followed by 6 practical recommendations. The neuroendocrine regulation of homeostasis will be emphasized in defense of the behavioral drives for thirst and sodium palatability during dynamic activities such as prolonged endurance exercise. The behavioral drives to maintain fluid and sodium balance are evolutionary stable, essential for the safety and survival of the species, and deeply rooted within the human genetic makeup.

Sodium supplementation is not required to maintain serum sodium concentrations during an Ironman triathlon

Context: Critical assessment of recommendations that athletes consume additional sodium during athletic events. Objective: To evaluate if sodium supplementation is necessary to maintain serum sodium concentrations during prolonged endurance activity and prevent the development of hyponatraemia. Design: Prospective randomised trial of athletes receiving sodium (620 mg table salt), placebo (596 mg starch), or no supplementation during a triathlon. The sodium and placebo tablets were taken ad libitum, with the suggested range of 1–4 per hour. Setting: The 2001 Cape Town Ironman triathlon (3.8 km swim, 180 km cycle, 42.2 km run). Subjects: A total of 413 triathletes completing the Ironman race. Main outcome measures: Sodium supplementation was not necessary to maintain serum sodium concentrations in athletes completing an Ironman triathlon nor required to prevent hyponatraemia from occurring in athletes who did not ingest supplemental sodium during the race. Results: Subjects in the sodium supplementation group ingested an additional 3.6 (2.0) g (156 (88) mmol) sodium during the race (all values are mean (SD)). There were no significant differences between the sodium, placebo, and no supplementation groups with regard to age, finishing time, serum sodium concentration before and after the race, weight before the race, weight change during the race, and rectal temperature, systolic and diastolic blood pressure after the race. The sodium supplementation group consumed 14.7 (8.3) tablets, and the placebo group took 15.8 (10.1) tablets (p  =  0.55; NS). Conclusions: Ad libitum sodium supplementation was not necessary to preserve serum sodium concentrations in athletes competing for about 12 hours in an Ironman triathlon. The Institute of Medicine’s recommended daily adequate intake of sodium (1.5 g/65 mmol) seems sufficient for a healthy person without further need to supplement during athletic activity.

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.

Left ventricular wall segment motion after ultra-endurance exercise in humans assessed by myocardial speckle tracking

AIMS Assessment of the left ventricular responses to prolonged exercise has been limited by technology available to assess cardiac tissue movement. Recently developed strain and strain rate imaging provide the unique opportunity to assess tissue deformation in all planes of motion. METHODS AND RESULTS Nineteen runners (mean+/-SD age; 41+/-9 years) were assessed prior to and within 60 min (34+/-10 min) of race finish (Comrades Marathon, 89 km). Standard echocardiography assessed ejection fraction and the ratio of early to atrial (E/A) peak transmitral blood flow velocities. Myocardial speckle tracking determined segmental strain as well as systolic and diastolic strain rates in radial, circumferential, and longitudinal planes. Cardiac troponin T (cTnT) assessed cardiomyocyte insult. Ejection fraction (71+/-5 to 64+/-6%) and E/A (1.47+/-0.35 to 1.25+/-0.30) were reduced (P<0.05). Peak strain and peak systolic and diastolic strain rates were altered post-race in circumferential (e.g. peak strain reduced from 21.3+/-2.4 to 17.3+/-3.2%, P<0.05) and radial planes. Some individual heterogeneity was observed between segments and planes of motion. A post-race elevation in cTnT (range 0.013-0.272 microg/L) in 5/12 runners did not differentiate changes in LV function. CONCLUSION Completion of the Comrades Marathon resulted in a depression in ejection fraction, E/A, as well as radial and circumferential strain and strain rates. Group data, however, masked some heterogeneity in cardiac function.

Maintenance of plasma volume and serum sodium concentration despite body weight loss in ironman triathletes.

Objective:To examine the relationship between body weight, plasma volume, and serum sodium concentration ([Na+]) during prolonged endurance exercise. Design:Observational field study. Settings:2000 South African Ironman Triathlon. Participants:181 male triathletes competing in an Ironman triathlon. Main Outcome Measures:Body weight, plasma volume, and serum ([Na+]) change from pre- to postrace. Results:Significant body weight loss occurred (−4.9 ± 1.7%; P < 0.0001), while both plasma volume (1.0 ± 11.2%; P = 0.4: NS) and serum [Na+] (0.6 ± 2.4%; P < 0.001) increased from pre- to postrace. Blood volume (−0.6 ± 6.6%) and red cell volume (−2.6 ± 5.5%; P < 0.001) decreased in conjunction with the body weight loss. There was a strong correlation between blood and plasma volume change, both as a percentage, and absolute change in fluid volume (r = 0.9; P < 0.001). Body weight change was positively correlated with plasma volume change (r = −0.4; P < 0.001), but inversely correlated with serum [Na+] change (r = −0.4; P < 0.001). Plasma volume change was not significantly correlated with serum [Na+] change (r = 0.0; NS). Serum [Na+] change was inversely correlated with both percentage of red cell volume change (r = −0.2; P < 0.05) and percentage body weight change (r = −0.4; P < 0.001). Conclusion:Plasma volume and serum [Na+] were maintained in male Ironman triathletes, despite significant (5%) body weight loss during the course of the race. Body weight was not an accurate “absolute” surrogate of fluid balance homeostasis during prolonged endurance exercise. Clinicians should be warned against viewing these three regulatory parameters as interchangeable during an Ironman triathlon.

Increasing Creatine Kinase Concentrations at the 161-km Western States Endurance Run

OBJECTIVE Very high blood creatine kinase (CK) concentrations have been observed among recent finishers of the 161-km Western States Endurance Run (WSER), and it has been suggested that there is a link between rhabdomyolysis and hyponatremia. Therefore, the purpose of this study was to compare CK concentrations of finishers in the 2010 WSER with past values, and to determine whether there was an association between blood CK and sodium concentrations. METHODS Consenting 2010 WSER finishers provided blood samples at the finish for determination of blood CK and sodium concentrations. Finish time, age, and gender were obtained from official race results, and running experience was determined from our database as number of prior 161-km ultramarathon finishes. RESULTS From 216 (66%) of the 328 finishers, median and mean CK concentrations were found to be 20 850 IU/L and 32 956 IU/L, respectively (range 1500-264 300 IU/L), and 13 (6%) had values greater than 100 000 IU/L. These values were statistically higher (P < .0001) than those reported from the 1995 WSER. The CK concentration was not significantly associated with finish time, age, gender, or running experience. Blood sodium concentrations were obtained from a subgroup of 159 runners, and the relationship between blood CK and sodium concentrations did not reach statistical significance (P = .06, r = -0.12). CONCLUSIONS Creatine kinase concentrations of 2010 WSER finishers are higher than values previously reported. More research should focus on explaining this observation and on whether there is a possible link between higher CK concentrations and hyponatremia.

Rhabdomyolysis and Hyponatremia: A Cluster of Five Cases at the 161-km 2009 Western States Endurance Run

OBJECTIVE Five of 400 starters of the 2009 Western States Endurance Run (WSER) were hospitalized with hyponatremia and rhabdomyolysis. This article explores the risk factors associated with development of hyponatremia and rhabdomyolysis. METHODS Data on the 5 cases were collected retrospectively from the runners and medical records, and all race participants were invited to complete a post-race survey. Characteristics of the cases were compared with the other race participants. RESULTS The 5 runners developing hyponatremia with rhabdomyolysis were men with a mean (±SD) age of 39 ± 7 years. Presenting complaints included neurological symptoms among 3 and nausea among 3. Compared with those runners not developing hyponatremia with rhabdomyolysis, the cases tended to be younger, faster, more likely to have sustained an injury which interfered with training prior to the race, and were more likely to use nonsteroidal anti-inflammatory drugs (NSAIDs) during the race. The 3 of 5 cases progressing to acute renal failure were characterized by higher initial blood urea nitrogen (BUN; 43-69 vs 18-23 mg/dL) and creatinine (2.8-4.9 vs 1.1-1.2 mg/dL) levels but were not distinguished by creatinine phosphokinase (CPK) concentrations. CONCLUSIONS Over 1% of participants in the 2009 WSER were hospitalized with hyponatremia in combination with rhabdomyolysis. These individuals tended to be younger, faster, more likely to have had an injury that interfered with training, and more likely to have used NSAIDs during the race. Higher initial BUN and creatinine levels, but not CPK concentrations, distinguished those 3 who progressed to acute renal failure.

An intervention study of oral versus intravenous hypertonic saline administration in ultramarathon runners with exercise-associated hyponatremia: a preliminary randomized trial.

Objective:To determine whether asymptomatic exercise-associated hyponatremia (EAH) in ultramarathon runners can be corrected with either oral or intravenous (IV) 3% hypertonic saline (HTS). Design:Prospective with randomization into 1 of 2 intervention arms. Setting:Western States (161 km) Endurance Run, California. Participants:Forty-seven finishers in the event consented to be screened to identify those with EAH, defined as plasma sodium ([Na+]p) <135 mmol/L at race end. Interventions:Participants with EAH but without symptoms were randomized to receive a single 100 mL dose of either oral or IV 3% HTS. Blood was drawn before intervention and at 60 minutes postintervention to measure [Na+]p, and concentrations of plasma potassium, proteins, and arginine vasopressin (AVP). Body mass, percent total body water, and percent body fat were measured prerace and postrace using impedance scales. Main Outcome Measures:Change in [Na+]p. Results:Fourteen of 47 consenting finishers (30%) had EAH. Eight agreed to be randomized into the intervention protocol. Only in the IV group did [Na+]p change significantly (from 130.8 to 134.6 mmol/L) over the 60 minutes post-HTS administration. Elevated AVP concentrations were seen at race finish in both the groups and remained so after HTS treatment. Conclusions:In this preliminary trial, prompt administration of a 100 mL bolus of IV 3% HTS was associated with normalization of [Na+]p in asymptomatic EAH, but a similar effect was not demonstrated for the same dose orally. Elevated AVP levels were observed and may play a part in the development of EAH but were not suppressed significantly by either intervention.