Randomised controlled trial of postnatal sodium supplementation on oxygen dependency and body weight in 25-30 week gestational age infants

Aim-To compare the effects of early against delayed sodium supplementation on oxygen dependency and body weight, in preterm infants of 25-30 weeks of gestational age. Methods-Infants were stratified by gender and gestation and randomly assigned to receive a sodium intake of 4 mmol/kg/day starting on either the second day after birth or when weight loss of 6% of birthweight was achieved. Daily sodium intake, serum sodium concentration, total fluid intake, energy intake, clinical risk index for babies (CRIB) score and duration of ventilatory support and additional oxygen therapy were recorded. Infants were weighed daily. Weights at 36 weeks and six months of postmenstrual age were also recorded. Results-Twenty four infants received early, and 22 delayed, sodium supplementation. There were no significant differences in total fluid and energy intake between the two groups. There was a significant difference in oxygen requirement at the end of the first week, with 9% of the early group in air in contrast to 35% of the delayed group (difference 26%, 95% confidence interval 2, 50). At 28 days after birth the proportions were 18% of the early group and 40% of the delayed group (difference 22%, 95% CI-5, 49). Proportional hazards modelling showed early sodium supplementation and lower birthweight to be significantly associated with increased risk of continuing oxygen requirement. The delayed sodium group had a greater maximum weight loss (delayed 16.1%; early 11.4%, p=0.02), but there were no significant differences in time to maximum weight loss, time to regain birthweight, and weight at 36 weeks and 6 months of postmenstrual age. Conclusion-In infants below 30 weeks of gestation, delaying sodium supplementation until at least 6% of birthweight is lost has a beneficial effect on the risk of continuing oxygen requirement and does not compromise growth.