Validity of urine-blood hydrational measures to assess total body water changes during mountaineering in the sub-Arctic.

Mountaineering involves high altitude and cold exposure which are each associated with significant levels of dehydration (via altitude-cold diuresis, high energy expenditures, and poor access to water). The purpose of this study was to identify and validate urine and blood indices of dehydration as compared to changes in total body water (which served as the reference standard). Male subjects (n = 10) were studied during a 14 day mountaineering expedition in the sub-Arctic during which they climbed to an altitude of 5245 +/- 229 m (mean +/- SE). Daily activity consisted of approximately 10-15 hours skiing, hiking, and performing mountaineering tasks with heavy loads (> 30 kg). Various measurements were made immediately before ascending (Pre) and after descending (Post) the mountain: body weight (Bw) and composition (%Fat), urine specific gravity (USG), urine protein (UP), plasma electrolytes (K+, Cl-, Na+), plasma proteins (PP), plasma and urinary osmolality (UOsm), hematocrit (Hct), hemoglobin (Hb), blood urea nitrogen (BUN), plasma aldosterone, and total body water (TBW determined via deuterium oxide). Post the expedition significant (p < 0.05) decreases were observed in Bw, and %Fat, while significant increases were found in Na+, K+, USG, UOsm and UP. TBW was slightly reduced, however, changes were non-significant (Pre = 52.9 +/- 1.2 L vs. Post = 52.6 +/- 1.3 L). USG is often used to monitor hydration status in field settings; however, no significant correlations were found between changes in TBW and USG, nor between changes in TBW and other typical urinary indicators of dehydration.(ABSTRACT TRUNCATED AT 250 WORDS)