Hypervolemia induced by fluid ingestion at rest: effect of sodium concentration
Sodium drink is used as a countermeasure against body fluid loss. However, high concentrations of sodium may cause gastrointestinal upset (e.g., diarrhea). We sought to determine the sodium concentration that induces hypervolemia with a minimal risk of gastrointestinal disturbance.
Eight healthy active males rested in a chair and ingested a given amount (16−17 ml kg body mass−1) of water (W) or solution containing 60, 120 or 180 mmol l−1 Na+ (60, 120 and 180Na trials) in 6 equal portions at 10 min intervals. To standardize their hydration status, subjects consumed the same meal and water 2 h before each trial. Drink trials were performed on separate days, and the order was randomized. The change in plasma volume (PV) from pre-drink status was estimated from the hemoglobin concentration and hematocrit every 30 min for 150 min after initiation of drinking.
Subjects began trials in a euhydrated state, as reflected by their plasma osmolality (in mmol l−1: W, 289.4 ± 1.4; 60Na, 287.0 ± 3.5; 120Na, 287.6 ± 2.3; 180Na, 288.9 ± 3.3). At 120 min, PV had not increased from the pre-drink value in the W (−0.8 ± 4.5 %) or 60Na (2.4 ± 4.9 %) trials, but it increased to similar degrees in the 120Na (7.2 ± 4.6 %) and 180Na (9.4 ± 6.6 %) trials. No diarrhea was reported in the W or 60Na trials, but it was reported in the 120Na (n = 1) and 180Na (n = 6) trials.
Beverages containing 120 mmol l−1 Na+ induce hypervolemia with a minimum incidence of gastrointestinal problems.
KeywordsHyperhydration Blood Extracellular fluid Fluid balance Fluid intake
Analysis of variance
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