RF01 | PMON158 Does Early Moderate Fluid Restriction Decrease Incidence of Delayed Hyponatremia Following Transsphenoidal Surgery? A Randomized Prospective Trial
Authors: Fong Brendan , Kim Albert , Yuan Jane , Blount Sydney , Hwang Jenie Y , Williams Kelley , Silverstein Julie 
Published: November 2022

Abstract

Background
Delayed hyponatremia is the most common cause for readmission after transsphenoidal surgery (TSS), occurring in up to 35% of patients. Due to lack of reliable predictive risk factors for the development of delayed hyponatremia, some institutions have implemented a post-operative fluid restriction for all patients undergoing TSS. Retrospective studies have demonstrated a reduction in the incidence of hyponatremia and readmission for hyponatremia after implementation of post-operative fluid restriction of varying volumes and duration. To our knowledge, a randomized prospective study on fluid restriction post-TSS has not been published previously. We present an interim analysis of a prospective randomized controlled study comparing two approaches to post-TSS fluid management.

Methods
Participants scheduled for TSS were randomly assigned to the control (CON, n=79) or fluid restriction group (FR1, n=38; FR2, n=37). Participants with chronic kidney disease stage III or greater, NYHA class III or IV heart failure, diabetes insipidus on postoperative day (POD) 3, chronic hyponatremia, or untreated adrenal insufficiency or hypothyroidism were excluded. All participants were started on postoperative weight-based intravenous fluids until POD 1 and allowed to drink freely. Participants in the initial fluid restriction group (FR1) were fluid restricted to 1.8 liters/day (2 liters/day if weight &gt; 100 kg) from POD 3 through POD 14. The fluid restriction was changed to 1 liter/day (1.2 liters/day if weight &gt; 100 kg) (FR2) during the study due to an interim analysis suggesting a trend toward a reduction in the incidence of hyponatremia with fluid restriction and new publications advocating for a tighter fluid restriction. Participants in the CON group were instructed to drink ad lib. Serum sodium (Na) levels were checked every 8 hours in the hospital and on POD 3, 7, 10, and 14. Incidence of hyponatremia (Na &lt; 135 mmol/L), severe hyponatremia (Na &lt; 125 mmol/L), and readmissions for hyponatremia were evaluated.

Results
There was no significant difference in baseline characteristics between the three groups. 25 participants (31.6%) in CON, 11 (28.9%) in FR1, and 9 (24.3%) in FR2 developed hyponatremia (FR2 vs CON, p=0.556). The incidence of severe hyponatremia was 0% in the FR2 group compared to 7.6% in the CON group (p=0.175). The rate of readmission for hyponatremia was 2.7% in the FR2 group compared to 6.3% in the CON group (p=0.71). There was no difference in the incidence of acute kidney injury or hypernatremia.

Conclusion
Preliminary results suggest a trend towards decreased rates of severe hyponatremia with 1L/day post-operative fluid restriction. A higher overall incidence of hyponatremia was noted in this interim analysis compared to previously published retrospective studies and may be related to increased screening in the current study. Further analysis with more participants is needed.
Presentation: Saturday, June 11, 2022 1:06 p.m. - 1:11 p.m., Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.