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Abstract: SA-OR032

Intense Renal Sodium Retention in Healthy Individuals Subjected to a Potassium Deprived Diet

Session Information

Category: Fluid and Electrolytes

  • 902 Fluid and Electrolytes: Clinical

Authors

  • Kowalski, Andrew, Northwestern University, Lombard, Illinois, United States
  • Batlle, Daniel, Northwestern University Feinberg Medical School, Chicago, Illinois, United States

Group or Team Name

  • Northwestern University Feinberg School of Medicine
Background

Diets poor in potassium (K) have been associated with hypertension, cardiovascular disease and all-cause mortality. Our study aims to quantify sodium (Na) balance in the setting of total dietary potassium deprivation of brief duration while keeping dietary sodium constant.

Methods

10 male healthy volunteers were studied in the clinical research unit while on a strict calorie and electrolyte balanced liquid diet for a 10 day control period followed by a 5 day study period with total dietary K deprivation. The Na intake was kept constant throughout the entire study period (1.8 mEq/KBW) and the intake of K was reduced from 1.5 mEq/KBW to 0 mEq/KBW. Body weights, systolic and diastolic blood pressure (SBP, DBP), serum and 24 hour urine electrolytes were collected daily.

Results

At the end of the control period, urinary K was 81 ± 8.6 mEq/24hrs and fell to 16 ± 1.68 mEq/24Hr (p=0.0006) by day 5 of the K deprived diet. After 5 days on a K deprived diet the cumulative K deficit was -132 ±10 mEq with a fall in plasma K from 4.54 ±0.15 to 3.68 ±0.05 mEq/dL (p=0.0016) by the end of the study period. Urinary Na excretion fell on day one on the K deprived diet, and by day 5 renal Na retention resulted in a positive Na balance of 507 ± 3.8 mEq/L. Bodyweight did not significantly increase during the initial 5 days of the study diet (from 91.6 ± 5.2kg to 91.8 ± 5.3kg; p=0.71). SBP at the end of 5 day increased slightly, but not significantly from 111.2 ± 2 .58 mmHg to 115.49 ± 2.94 mmHg; p=0.083, and DBP decreased but not significantly from 72.6 ± 1.6 mmHg to 71.3 ± 2.4mmHg; p=0.50. There was a marked fall in hematocrit by day 5 with a fall from 45.6 ± 0.53% to 42 ± 0.44% (p=0.01). From the change in hematocrit and body weight plasma volume was estimated to have increased by 192mL (from 3483 ± 379 mL to 3675 ± 409 mL; p=0.005) over the 5 day period.

Conclusion

This study shows that total dietary K deprivation is a potent stimulus for the kidney to rapidly retain Na over a very short period of time. Even more striking was the observed magnitude of the positive Na balance of 507 mEq/L with only a small increase in plasma volume along with no significant increase in body weight or blood pressure. This observation supports recent evidence of a large Na reservoir with the ability to store significant amounts of Na, thus limiting its impact on body weight and blood pressure.

Funding

  • NIDDK Support