Comparison of isotonic versus hypotonic intravenous fluid for maintenance fluid therapy in neonates more than or equal to 34 weeks of gestational age - a randomized clinical trial.

Background and objectives: The use of hypotonic fluids as maintenance therapy in the neonatal population has been in practice for a long time, but there is a lack of evidence for the choice of this fluid in neonates. This study compared isotonic (sodium chloride, 0.9%, and dextrose, 5%) versus hypotonic (sodium chloride, 0.15%, and dextrose, 5%) intravenous fluid for maintenance fluid therapy in neonates more than or equal to 34 weeks of gestational age.

Methods: In this triple-blind randomized clinical trial, we recruited 60 neonates admitted to a neonatal intensive care unit of a tertiary care children's hospital from June 2017 through May 2018 with normal baseline serum sodium levels, anticipated to require intravenous maintenance fluids for 24 hours or longer (intention-to-treat analyses). Patients were randomized to receive isotonic or hypotonic intravenous fluid at maintenance rates for 72 hours. The primary outcome was the incidence of hyponatremia (defined as serum sodium <135mEq/L) at 24 hours in both groups. The secondary outcomes were incidence of hypernatremia at 24 hours (defined as serum sodium >145 mEq/L), the incidence of hypo and hypernatremia at 48 and 72 hours, mean serum sodium at 24, 48, and 72 hours, rate of change of serum sodium during the study period, mean serum osmolality at the end of the study period, the absolute difference in osmolality during the study period, the absolute difference in weight during the study period and edema during the study period.

Results: Of 60 enrolled neonates, 31 received isotonic fluids and 29 received hypotonic fluids. Three patients in the hypotonic group developed hyponatremia and none in isotonic group at 24 h (RR = 0.13; 95% CI = 0.007 - 2.485; p = .106). Fourteen neonates developed hypernatremia in the isotonic group and one in hypotonic group at 24 h (RR = 13.09; 95% CI = 1.83 - 93.4; p = .0001).

Conclusions: Our study results do not support the hypothesis that isotonic fluid is superior to hypotonic fluid in reducing the proportion of neonates developing hyponatremia after 24 hours of intravenous fluid therapy. The proportion of neonates developing hypernatremia is significantly higher after using isotonic fluid for maintenance therapy. TRIAL REGISTRATION CTRI/2017/05/008585.