Predictive factors for early-onset hyponatremia following endoscopic transsphenoidal surgery for nonfunctioning pituitary adenomas

OBJECTIVE The goal of this study was to characterize the pre-, peri-, and postoperative risk factors associated with early hyponatremia (defined as a serum sodium level < 135 mEq/L on or before postoperative day [POD] 3) following transsphenoidal pituitary surgery. METHODS This retrospective study was performed using a single-institution database for patients undergoing surgery for pituitary adenoma (PA). Serum values were collected routinely throughout the postoperative period. Uni- and multivariable statistical analyses were performed to identify independent predictors of early hyponatremia. Patients with diabetes insipidus receiving desmopressin were excluded from the analysis. RESULTS Of 254 patients with nonfunctional PAs (NFPAs), 65 (25.6%) developed early-onset hyponatremia. Univariable analysis showed that older age, higher preoperative serum sodium, higher preoperative serum glucose, BMI > 30 kg/m 2 , and pituitary apoplexy were significantly associated with early hyponatremia (p < 0.05). Multivariable logistic regression modeling revealed that the factors most strongly associated with early hyponatremia were thiazide diuretic use (OR 7.84, 95% CI 1.01–72.11; p = 0.049), pituitary apoplexy (OR 21.33, 95% CI 2.86–271.37; p = 0.006), preoperative glucose level (OR 1.16 per 10 mg/dl, 95% CI 1.02–1.36; p = 0.032), and BMI > 27 kg/m 2 (OR 0.05, 95% CI 0.00–0.36; p = 0.010). CONCLUSIONS Early-onset hyponatremia is a common electrolyte derangement following transsphenoidal pituitary surgery for NFPAs. Clinical factors including low BMI, thiazide diuretic use, and elevated preoperative serum glucose were associated with an increased risk of early-onset hyponatremia. Higher BMI, in contrast, was protective against early-onset hyponatremia. Understanding the factors related to postoperative hyponatremia can aid in earlier detection, monitoring, and treatment for high-risk patients following PA surgery.