Post-operative Fluid Restriction to Prevent Delayed Hyponatremia after Endoscopic Transsphenoidal Surgery

Abstract Background Readmission following endoscopic endonasal transsphenoidal surgery (EETS) for pituitary neuroendocrine tumor (PitNET) and other sellar pathology is most commonly due to delayed hyponatremia. Studies suggest post-operative fluid restriction (FR) reduces delayed hyponatremia. We present a prospective randomized controlled study evaluating post-EETS FR. Methods 300 participants were scheduled for EETS (2016-2023) at a single institution. Patients with CKD, CHF, arginine vasopressin deficiency on post-operative day (POD) 3, chronic hyponatremia, and untreated adrenal insufficiency or hypothyroidism were excluded. Groups included control (ad-lib, n=94), moderate FR (1.8 L/day or 2 L/day weight >100 kg, n=39), and strict FR (1 L/day or 1.2 L/day weight >100 kg, n=62) from POD 3-14. Incidence of overall, moderate, and severe hyponatremia (Na <135, 125-129, and <125 mEq/L), readmission rates, fluid intake, and thirst were evaluated. Results The incidence of overall hyponatremia was 31.9%, 28.2%, and 21.0% in control, moderate FR, and strict FR groups, and the incidence of severe hyponatremia was 7.4%, 5.1%, and 0% in control, moderate FR, and strict FR groups. Nadir Na level was higher (1.81 mEq/L; 95% CI, 0.34 to 3.27; P=0.02) and severe hyponatremia occurred less frequently (95% CI, 0.00 to 1.02; P=0.04) in the strict FR vs. control group. Readmission was lower in the strict FR (1.6%, n=1) vs. control group (6.4%, n=6). Conclusion Post-operative FR decreases rates of delayed hyponatremia and related readmission compared to patients drinking ad-lib. Further studies are needed to assess the optimal volume and duration of FR after EETS.