Related Experiment Video
Updated: Aug 1, 2026
Use of a Hanging-weight System for Isolated Renal Artery Occlusion
Published on: July 19, 2011
Renal function in sick very low birthweight infants: 3. Sodium, potassium, and water excretion
1Department of Child Health, Bristol University.
Insights
Premature infants show significant daily variations in water, sodium, and potassium excretion. Most infants experience hyponatremia, while high sodium and potassium excretion are common in the early postnatal period, especially in immature infants.
Area of Science:
- Neonatal Physiology
- Pediatric Nephrology
Background:
- Infants born prematurely (25.5-33 weeks gestation) have immature renal systems.
- Understanding electrolyte and water balance is crucial for neonatal care.
Purpose of the Study:
- To quantify renal excretion of sodium, water, and potassium in preterm infants.
- To identify patterns and potential complications related to these excretions.
Main Methods:
- Measured renal excretion of sodium, water, and potassium in 40 preterm infants (0.5-36 days old).
- Analyzed data in relation to gestational age, birth weight, and postnatal age.
- Correlated findings with electrolyte imbalances like hyponatremia and hyperkalemia.
Main Results:
- Wide daily variations in water excretion (1-30% of GFR).
- Nearly all infants developed hyponatremia post-birth.
- High sodium excretion (up to 16% of filtered sodium) observed, particularly in the most immature infants.
- Elevated potassium excretion (up to 96% of filtered potassium) linked to early hyperkalemia.
Conclusions:
- Preterm infants exhibit significant renal immaturity affecting water and electrolyte homeostasis.
- Close monitoring of sodium and potassium balance is essential in the neonatal intensive care unit.
- Hyponatremia and hyperkalemia are common challenges in this vulnerable population.
Abstract:
Renal excretion of sodium, water, and potassium was measured on 434 occasions in a sample of 40 infants of 25.5-33 weeks' gestation, birth weight 720-2000 g, between the ages of 0.5 and 36 days. Water excretion varied between 1% and 30% of the glomerular filtration rate, or 15-350 ml/kg/day, and varied widely from day to day in individual infants. Nearly all infants became hyponatraemic before or after the first postnatal week. There were a few instances of hypernatraemia in the first week caused by high insensible water loss. There were high levels of sodium excretion up to 16% of filtered sodium, or 21 mmol/kg/day, in the first two postnatal weeks. Highest levels of sodium excretion were seen in the most immature infants in the first week. In most infants sodium excretion increased either in the first week or later before a subsequent decline. Potassium excretion was often high in the first week, as much as 96% of filtered potassium, or 5 mmol/kg/day, and is associated with early hyperkalaemia.
Related Concept Videos
01:25Regulation of Water Intake
01:26Regulation of Water Output
01:26Regulation of Sodium and Potassium
Sodium Regulation
Sodium ions make up approximately 90% of extracellular cations, with a normal blood plasma concentration of 136–148 mEq/L. A decrease in blood volume and pressure triggers the release of renin from granular cells in the juxtaglomerular complex (JGC), primarily in...
01:22Physiology of the Genitourinary System II: Tubular Reabsorption and Secretion
01:20Physiology of the Genitourinary System III: Urine Concentration and Dilution
01:20Acute Kidney Injury V: Interprofessional Care