Hyponatremia is not induced by postoperative hypotonic fluids in infants with biliary atresia after sufficient diuresis.

Background: In Japan, the administration of extra-hypotonic fluids (approximately 35 mmol/L of sodium) as maintenance fluid is still the mainstream practice, and there have been relatively few reports on maintenance intravenous fluid therapy. Since 2014, our institution has administered maintenance fluids containing 83 mmol/L of Na (HALF) after diuresis is achieved post-Kasai portoenterostomy for biliary atresia (BA). We investigated whether hyponatremia is induced by the administration of half saline during postoperative maintenance of infants with BA.

Methods: Patients who underwent surgery for BA at our institution were included. The serum sodium concentration ([Na]) before and after surgery and the incidence of hyponatremia were compared between patients administered fluids with [Na] of 35 mmol/L (exHYPO group, 59 patients) and those with [Na] of 83 mmol/L (HALF group, 20 patients).

Results: The median age of patients was 59 days. There were no significant differences in the background or preoperative [Na] between groups. There was a significant decrease in [Na] on postoperative day 3 (POD3) in the exHYPO group compared with the preoperative [Na] value in the exHYPO group and the [Na] value on POD3 in the HALF group. There were no significant differences in [Na] before and after surgery in the HALF group. The odds ratio was 21.0, and the 95% confidence interval was 3.31-130, indicating that the exHYPO group had an increased risk of hyponatremia.

Conclusion: Administration of half saline as maintenance fluid can maintain [Na] levels during postoperative care of infants with BA.