Saline versus balanced crystalloids for hydration post-kidney biopsy.

Background: Isotonic fluids are becoming the standard for hydration and maintenance fluid therapy, but there is no consensus on the optional choice among the different types of isotonic solution.

Methods: This study is a single-center, non-randomized controlled trial at Kobe University Hospital, Japan, between April 2021 and March 2023. The study included pediatric patients aged 1-19 years who underwent kidney biopsies. From April 2021 to March 2022, 0.9% sodium chloride (saline) was administered, and from April 2022 to March 2023, balanced crystalloids were used. The primary outcome was the occurrence of hyponatremia (< 137 mEq/L) after a kidney biopsy. Secondary outcomes included other electrolyte balances, blood gas parameters, creatinine-based estimated glomerular filtration rate (Cr-eGFR), and arginine vasopressin concentrations (UMIN Clinical Trial Registry: UMIN 000044330).

Results: Of 61 patients enrolled, 2 were excluded, leaving 34 in the saline group and 25 in the balanced crystalloid group. No hyponatremia occurred, and serum sodium concentrations were similar between both groups (138.7 vs. 138.9 mEq/L, P = 0.08). The saline group showed a greater increase in serum chloride (+ 1.7 vs. + 0.2, P < 0.01) and a greater decrease in HCO₃^- concentrations (- 0.6 vs. + 0.9, P < 0.01). There were minimal changes in pH (- 0.01 vs. - 0.01, P = 0.99) and Cr-eGFR (- 1.5 vs. + 1.1 mL/min/1.73 m², P = 0.96) in both groups.

Conclusions: During pediatric kidney biopsy, both saline and balanced crystalloids were effective in preventing hyponatremia. Although saline infusion results in higher serum chloride concentrations and lower blood HCO₃^- concentrations than balanced crystalloids infusion, the clinical significance was minimal.