Carbohydrate hastens hypervolemia achieved through ingestion of aqueous sodium solution in resting euhydrated humans.

PURPOSE: Ingesting beverages containing a high concentration of sodium under euhydrated conditions induces hypervolemia. Because carbohydrate can enhance interstitial fluid absorption via the sodium-glucose cotransporter and insulin-dependent renal sodium reabsorption, adding carbohydrate to high-sodium beverages may augment the hypervolemic response. METHODS: To test this hypothesis, we had nine healthy young males ingest 1087 ± 82 mL (16-17 mL per kg body weight) of water or aqueous solution containing 0.7% NaCl, 0.7% NaCl + 6% dextrin, 0.9% NaCl, or 0.9% NaCl + 6% dextrin under euhydrated conditions. Each drink was divided into six equal volumes and ingested at 10-min intervals. During each trial, participants remained resting for 150 min. Measurements were made at baseline and every 30 min thereafter. RESULTS: Plasma osmolality decreased with water ingestion (P ≤ 0.023), which increased urine volume such that there was no elevation in plasma volume from baseline (P ≥ 0.059). The reduction in plasma osmolality did not occur with ingestion of solution containing 0.7% or 0.9% NaCl (P ≥ 0.051). Consequently, urine volume was 176-288 mL smaller than after water ingestion and resulted in plasma volume expansion at 60 min and later times (P ≤ 0.042). In addition, net fluid balance was 211-329 mL greater than after water ingestion (P ≤ 0.028). Adding 6% dextrin to 0.7% or 0.9% NaCl solution resulted in plasma volume expansion within as little as 30 min (P ≤ 0.026), though the magnitudes of the increases in plasma volume were unaffected (P ≥ 0.148). CONCLUSION: Dextrin mediates an earlier hypervolemic response associated with ingestion of high-sodium solution in resting euhydrated young men. (247/250 words).

Hypervolemia induced by fluid ingestion at rest: effect of sodium concentration.

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: Beverages containing 120 mmol l(-1) Na(+) induce hypervolemia with a minimum incidence of gastrointestinal problems.