Renal phosphate handling of premature infants of 23-25 weeks gestational age

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Gerald Hellstern1, Johannes Pöschl, Otwin Linderkamp

  • 1Department of Neonatology, University of Heidelberg Children's Hospital, Im Neuenheimer Feld 150, 69120, Heidelberg, Germany. gerald_hellstern@med.uni-heidelberg.de

Pediatric Nephrology (Berlin, Germany)
|June 5, 2003
PubMed

Insights

Extremely premature infants (23-25 weeks gestational age) excrete phosphate even with low serum levels. Careful monitoring and phosphate supplementation are crucial for these vulnerable infants to prevent osteopenia.

Area of Science:

  • Neonatology
  • Pediatric Nephrology
  • Biochemistry

Background:

  • Premature infants, especially those with low serum phosphate (<2 mmol/l), face risks of osteopenia.
  • Maintaining adequate serum phosphate levels (>2 mmol/l) is vital for premature infants.
  • Renal phosphate handling and excretion patterns differ based on gestational age.

Purpose of the Study:

  • To compare renal phosphate threshold (Tp/GFR) levels in extremely premature infants (23-25 weeks gestational age) versus moderately premature infants (26-31 weeks gestational age).
  • To assess the risk of urinary phosphate excretion in different gestational age groups.
  • To inform phosphate supplementation strategies for premature infants.

Main Methods:

  • Retrospective case note evaluation of 12 infants (23-25 weeks GA) and 19 infants (26-31 weeks GA).
  • Calculation of renal phosphate threshold (Tp/GFR) using simultaneous measurements of urinary and serum phosphate and creatinine.
  • Comparison of Tp/GFR values at 3-5 weeks postnatal and near-term (35-37 weeks postmenstrual age).

Main Results:

  • Infants of 23-25 weeks GA exhibited significantly lower Tp/GFR values (1.06+/-0.36 mmol/l) at 3-5 weeks postnatal compared to infants of 26-31 weeks GA (1.76+/-0.26 mmol/l).
  • No significant difference in Tp/GFR was observed between the groups near term (35-37 weeks postmenstrual age).
  • Lower Tp/GFR in extremely premature infants indicates risk of phosphate wasting even with low serum phosphate levels.

Conclusions:

  • Extremely premature infants (23-25 weeks GA) are at risk for low renal phosphate threshold concentrations early in life.
  • These infants may excrete phosphate significantly, necessitating close serum phosphate monitoring.
  • Phosphate supplementation should be individualized and adjusted to maintain serum phosphate levels above 2 mmol/l in this population.

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