Incidence of hyponatremia with different postoperative intravenous maintenance fluids: a single-center, prospective,...

Patients undergoing surgery are prone to postoperative hyponatremia, which can lead to delirium. However, the optimal sodium concentration for postoperative maintenance fluids in adult patients is still unclear. Therefore, this study examined the incidence of hyponatremia and delirium in postoperative patients.

This was a single-center, non-blinded, randomized trial. The inclusion criteria for this study were age 20 years or older and elective head and neck cancer or esophageal cancer surgery between April 2018 and June 2023. Patients were randomly assigned to one of three groups based on the sodium concentration in the intravenous fluids administered after surgery: the 140 mmol/L sodium (Na₁₄₀) group, the 77 mmol/L sodium (Na₇₇) group, and the 35 mmol/L sodium (Na₃₅) group.

A total of 105 patients had complete data at the end of the study: Na₁₄₀ group (n = 35), Na₇₇ group (n = 32), and Na₃₅ group (n = 38). The incidence of postoperative hyponatremia was 22.9% (8/35) in the Na₁₄₀ group, significantly lower than in the Na₇₇ group [56.3% (18/32)] and the Na₃₅ group [60.5% (23/38)] (both p < 0.01). The incidence of postoperative delirium was 20.0% (7/35) in the Na₁₄₀ group, 31.3% (10/32) in the Na₇₇ group, and 23.7% (9/38) in the Na₃₅ group. No significant difference was observed among the groups (p = 0.56).

The use of postoperative fluids with a sodium concentration of 140 mmol/L significantly reduced the incidence of hyponatremia. There was no significant difference in the incidence of postoperative delirium.