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Circadian variations of urinary electrolyte concentrations in preterm and term infants
A Trotter1, M Stoll, J U Leititis
1Division of Neonatology and Pediatric Critical Care Medicine, Children's Hospital, University of Ulm, Germany.
Insights
This study found no significant daily rhythm in the urinary excretion of calcium and phosphorus in preterm infants. Therefore, the timing of urine collection does not impact the assessment of mineral balance in these vulnerable newborns.
Area of Science:
- Neonatal Medicine
- Pediatric Nephrology
- Circadian Biology
Background:
- Preterm infants often require careful monitoring of mineral balance, particularly calcium and phosphorus, due to their immature physiological systems.
- Understanding diurnal variations in urinary mineral excretion is crucial for accurate assessment and management of metabolic homeostasis in neonates.
- Previous research on circadian rhythms in mineral excretion has yielded varied results, necessitating specific investigation in preterm populations.
Purpose of the Study:
- To investigate the presence of a circadian variation in the urinary excretion of calcium and phosphorus in preterm infants.
- To determine if the time of day for urine sample collection influences the measurement of mineral excretion in this population.
Main Methods:
- A cohort of 70 preterm infants with varying birth weights and gestational ages was studied.
- Four urine specimens were collected from each infant over a 24-hour period at 6-hour intervals.
- Urinary concentrations of calcium, phosphorus, sodium, potassium, and creatinine were measured, and creatinine quotients were calculated.
Main Results:
- No clinically significant circadian variation was observed in the urinary excretion of calcium or phosphorus.
- The concentrations of other measured electrolytes (sodium, potassium) also did not show a relevant diurnal pattern.
Conclusions:
- The time of day for collecting spot urine specimens is not a critical factor when monitoring calcium and phosphorus balance in preterm infants.
- These findings simplify the clinical practice of assessing mineral status in neonates, allowing for flexible urine sample collection.
- Further research could explore other factors influencing mineral excretion patterns in preterm infants.
Objectives:
To determine whether a circadian variation of urinary excretion of calcium and phosphorus exists in preterm infants.
Study Design:
We studied 70 newborn infants (median birth weight 1920 gm, range 660 to 3550 gm; median gestational age 34 weeks, range 25 to 42 weeks) at a median postmenstrual age of 36 weeks (range 32 to 42 weeks). Within a period of 24 hours, four urine specimens were collected during 6-hour periods. The concentrations of calcium, phosphorus, sodium, potassium, and creatinine were determined and creatinine quotients were calculated for each specimen.
Results:
No clinically relevant circadian variation in urinary excretion for any of these minerals was found.
Conclusion:
If spot urine specimens are used to monitor calcium and phosphorus balance in preterm infants, the time of the day these are collected is not important.