Evaluation of salt supplementation in CF infants

J Cyst Fibros. 2009 Dec;8(6):382-5. doi: 10.1016/j.jcf.2009.08.006. Epub 2009 Oct 2.


Background: CF infants may be at increased risk of sodium depletion which may lead to impaired growth. The objective of this study was to evaluate their sodium supplementation requirements.

Methods: Ten CF infants had serial measurements of weight and plasma/urine sodium and creatinine. Sodium supplementation was adjusted with the aim of maintaining fractional excretion (FENa) between 0.5% and 1.5% and urinary sodium > 10 mmol/L.

Results: Urine sodium:creatinine (UNa:Cr) ratio strongly correlated with FENa [UNa:Cr (mmol/mmol)=35.0 x FENa (r=0.99)]. The FENa target range corresponded to UNa:Cr 17-52 mmol/mmol. All infants required sodium supplementation to achieve UNa:Cr > 17 mmol/mmol. Sodium supplement requirements (mean+/-SD) at ages 0-3, 3-6, 6-9 and 9-12 months were 1.9+/-0.5, 1.8+/-0.8, 1.9+/-0.9 and 0.8+/-0.4 mmol/kg/d. No infant required calorie supplementation to achieve expected weight gain.

Conclusions: Using current UK guidelines, many cases of sodium depletion may be overlooked. Some infants require more than the recommended 1-2 mmol/kg/d. UNa:Cr ratio is a useful non-invasive measure to monitor sodium supplementation.

Publication types

  • Clinical Trial

MeSH terms

  • Adolescent
  • Body Weight
  • Creatinine / urine
  • Cystic Fibrosis / diet therapy*
  • Cystic Fibrosis / metabolism
  • Female
  • Humans
  • Hyponatremia / blood
  • Hyponatremia / diet therapy*
  • Hyponatremia / urine
  • Infant, Newborn
  • Infant, Newborn, Diseases / diet therapy*
  • Infant, Newborn, Diseases / metabolism
  • Male
  • Sodium Chloride, Dietary / administration & dosage*
  • Sodium Chloride, Dietary / pharmacokinetics


  • Sodium Chloride, Dietary
  • Creatinine