Hydration Status as Predictor of Summit Success on Mount McKinley

Abstract

As thousands of people attempt high-altitude peaks each year, euhydration is promoted for optimal climbing performance and dehydration is viewed as a potential detriment. This study was the first to define hydration status at high altitude by ultrasound measurements and correlate this with summit success (SS). A prospective observational cohort study enrolled climbers between the ages of 18 and 65 who had been at 14,000 ft (4267 m) for less than 24 hours on Mount McKinley, Alaska during June 2013. Participants completed a survey about water-carrying capacity and intake and had state of hydration evaluation determined by urine specific gravity (SG) and ultrasound measurements of the inferior vena cava (IVC) collapsibility index. Upon returning to 14,000 ft after their summit attempt, climbers reported maximum elevation gained. An independent two-sample t test was performed for independent variables with binary logistic regression for the identified significant predictors. One-hundred twenty-one participants enrolled, with 100 (86%) complete data sets and 67% successful summiters. There was no significant association with SS and IVC collapsibility (50.4% vs 52.4% ± 1.9%, P = .52), IVC size (0.96 cm vs 0.99 cm ± 0.03 cm, P = .63), or SG (1.02 vs 1.02 ± 0.001, P = .64). Successful summiters estimated they consumed more water (3.4 L/day vs 3 L/day ± 0.4 L/day, P = .049) than non-summiters, though this significance was not seen in the regression analysis. Ultrasound measurements did not appear to have a diagnostic role in predicting dehydration or high-altitude performance by summit success. While ultrasound measurements indicated that climbers were dehydrated, specific gravity measurements suggested climbers were euvolemic (average SG 1.02). A trend was seen that greater water consumption might have increased chances for SS. Increasing water-carrying capacity is an inexpensive and easy intervention that may improve SS in climbers ascending to high altitudes.