Efficacy of oral versus intravenous hypertonic saline in runners with hyponatremia.

OBJECTIVES: To determine more conclusively whether intravenous (IV) administration of 3% saline is more efficacious than oral administration in reversing below normal blood sodium concentrations in runners with biochemical hyponatremia. DESIGN: Randomized controlled trial. METHODS: 26 hyponatremic race finishers participating in the 161-km Western States Endurance Run were randomized to receive either an oral (n=11) or IV (n=15) 100mL bolus of 3% saline. Blood sodium concentration (Na(+)), plasma protein (to assess %plasma volume change), arginine vasopressin (AVP), blood urea nitrogen (BUN) and urine (Na(+)) were measured before and 60 min following the 3% saline intervention. RESULTS: No significant differences were noted with respect to pre- to post-intervention blood [Na(+)] change between intervention groups, although blood [Na(+)] increased over time in both intervention groups (+2 mmol/L; p<0.0001). Subjects receiving the IV bolus had a greater mean (± SD) plasma volume increase (+8.6 ± 4.5% versus 1.4% ± 5.7%; p<0.01) without significant change in [AVP] (-0.2 ± 2.6 versus 0.0 ± 0.5 pg/mL; p=0.49). 69% of subjects completing the intervention trial were able to produce urine at race finish with a mean (± SD) pre-intervention urine [Na(+)] of 15.2 ± 8.5 mmol/L (range 0-35; NS between groups). [BUN] of the entire cohort pre-intervention was 30.7 ± 10.5mg/dL (range 13-50). CONCLUSIONS: No group difference was noted in the primary outcome measure of change in blood [Na(+)] over 60 min of observation following a 100mL bolus of either oral or IV 3% saline. Administration of an oral hypertonic saline solution can be efficacious in reversing low blood sodium levels in runners with mild EAH.

Characteristics of 161-km ultramarathon finishers developing exercise-associated hyponatremia.

This study sought to identify runner characteristics or symptoms that could distinguish those finishers developing exercise-associated hyponatremia (EAH) from those not developing EAH in a 161-km ultramarathon. Of 310 finishers, 207 (67%) underwent postrace blood studies. Twelve (6%) finishers had EAH (blood sodium range 131-134 mmol/L). Experience at 161-km ultramarathons was lower (p = 0.01) and blood creatine kinase (CK) concentration was higher (p = 0.04) among those with EAH than those not developing EAH. Blood sodium and CK concentration were negatively correlated (p = 0.0015, r = -0.22). There were no group differences in age, sex, regular running experience, weekly training distance, use of sodium supplements during training, immediately postrace sodium palatability and thirst ratings, body mass change, urination frequency, nonsteroidal anti-inflammatory drugs (NSAIDs) use, and various symptoms experienced during the race. These findings indicate that a clinical suspicion and measurement of blood sodium concentration remain the only viable means for determining when an ultramarathon runner has EAH.

The effect of physiology and hydration beliefs on race behavior and postrace sodium in 161-km ultramarathon finishers.

PURPOSE: To determine if beliefs about physiology and rehydration affect ultramarathon runners' hydration behaviors or if these beliefs increase the risk for exercise-associated hyponatremia (EAH). METHODS: Participants of the 2011 161-km Western States Endurance Run completed a prerace questionnaire, prerace and postrace body-mass measurements, and postrace assessment of serum sodium ([Na⁺]). RESULTS: Of 310 finishers, 309 (99.7%) completed the prerace questionnaire and 207 (67%) underwent postrace blood studies. Twelve (5.8%) finishers had asymptomatic EAH ([Na⁺] range 131-134 mmol/L). The most common hydration plan (43.1%) was drinking according to schedule, and these runners did so to replace fluid lost when sweating (100%) and to avoid dehydration (81.2%). Prerace drinking plan was not associated with postrace [Na⁺] or the development of postrace hyponatremia. There also were no group differences between those with and those without EAH for any other variables including planned energy intake or knowledge of fluid balance. Runners not planning to drink to thirst trended toward more influence from advertisements (P = .056) and were significantly more influenced by scientific organizations (P = .043) than runners with other drinking plans. Finally, runners who believe that EAH is caused by excessive drinking adopted a lower-volume drinking plan (P = .005), while runners who believe that EAH is caused by sodium loss via sweating reported more common use of sodium supplementation during the race (P = .017). CONCLUSIONS: Beliefs regarding the causes of EAH alter race behaviors including drinking plan and sodium supplementation but do not appear to affect the likelihood of developing EAH during a 161-km ultramarathon.

Urine dipstick analysis for identification of runners susceptible to acute kidney injury following an ultramarathon.

This study examined whether urine dipstick testing might be useful to predict the development of acute kidney injury after an ultramarathon. Participants in the 2011 161-km Western States Endurance Run underwent post-race blood and urine dipstick analyses. Of the 310 race finishers, post-race urine dipstick testing was completed on 152 (49%) and post-race blood also was obtained from 150 of those runners. Based on "injury" and "risk" criteria for acute kidney injury of blood creatinine 2.0 and 1.5 times estimated baseline, respectively, 4% met the criteria for injury and an additional 29-30% met the criteria for risk of injury. Those meeting the injury criteria had higher creatine kinase concentrations (P < 0.001) than those not meeting the criteria. Urine dipstick tests that read positive for at least 1+ protein, 3+ blood, and specific gravity ≥ 1.025 predicted those meeting the injury criteria with sensitivity of 1.00 (95% confidence interval [CI] 0.54-1.00), specificity of 0.76 (95% CI 0.69-0.83), positive predictive value of 0.15 (95% CI 0.06-0.30), negative predictive value of 1.00 (95% CI 0.97-1.00), and likelihood ratio for a positive test of 4.2. We conclude that urine dipstick testing was successfully able to identify those individuals meeting injury criteria for acute kidney injury with excellent sensitivity and specificity.

Demographic characteristics of 161-km ultramarathon runners.

Despite considerable recent growth in ultramarathon running, little is known about the characteristics of the participants. This work documents demographic characteristics of 161-km ultramarathoners. Surveys were completed by 489 of 674 runners entered in two of the largest 161-km ultramarathons in North America in 2009. Respondents had a mean (± SD) age of 44.5 ± 9.8 years (range 20-72 years) and were generally men (80.2%), married (70.1%), had bachelor's (43.6%) or graduate (37.2%) degrees, and used vitamins and/or supplements (75.3%). They reported 2.8 ± 20.2 days of work or school loss in the previous year from injury or illness. Body mass index (23.4 ± 2.2 and 20.8 ± 1.8 kg/m2 for men and women, respectively) was not associated with age. The findings indicate that 161-km ultramarathon participants are largely well-educated, middle-aged, married men who rarely miss work due to illness or injury, generally use vitamins and/or supplements, and maintain appropriate body mass with aging.

Factors related to successful completion of a 161-km ultramarathon.

PURPOSE: Despite increased 161-km ultramarathon participation in recent years, little is known about those who pursue such an activity. This study surveyed entrants in two of the largest 161-km trail ultramarathon runs in North America to explore demographic characteristics and issues that affected race performance. METHODS: All entries of the 2009 Western States Endurance Run and the Vermont 100 Endurance Race were invited to complete a postrace questionnaire. RESULTS: There were 500 respondents among the 701 race entries (71.3% response). Finish time was found to have a significant (P ≤ .01) negative association with training volume and was generally directly associated with body mass index. Among nonfinishers, the primary reason for dropping out was nausea and/or vomiting (23.0%). Finishers compared with nonfinishers were more likely (P ≤ .02) to report blisters (40.1% vs 17.3%), muscle pain (36.5% vs 20.1%), and exhaustion (23.1% vs 13.7%) as adversely affecting race performance, but nausea and/or vomiting was similar between groups (36.8% vs 39.6%). Nausea and/or vomiting was no more common among those using nonsteroidal anti-inflammatory drugs (NSAIDs), those participating in the event with higher ambient temperatures, those with a lower training volume, or those with less experience at finishing 161-km races. Overall use of NSAIDs was high, and greater (P = .006) among finishers (60.5%) than nonfinishers (46.4%). CONCLUSIONS: From this study, we conclude that primary performance-limiting issues in 161-km ultramarathons include nausea and/or vomiting, blisters, and muscle pain, and there is a disturbingly high use of NSAIDs in these events.