Incidence and risk factors of hyponatremia after transsphenoidal surgery: a systematic meta-analysis

The transsphenoidal approach to sellar lesions is a mainstay technique in modern neurosurgical treatment of pituitary adenomas. One prominent complication following transsphenoidal surgery is the development of postoperative hyponatremia, frequently necessitating additional medical management and hospital readmission. However, the precise incidence and risk factors of postoperative hyponatremia remain unclear in the current literature. We conducted a systematic meta-analysis of 104 studies (31,676 patients) to clarify the incidence of postoperative hyponatremia and associated hospital readmission, as well as to summarize conflicting findings regarding significant risk factors of postoperative hyponatremia. The overall incidence of postoperative hyponatremia following transsphenoidal surgery was 13.3% [95% Confidence Interval (CI): 11.8-14.7%; 96 studies]. The rate of hospital readmission due to postoperative hyponatremia was 3.3% [95% CI: 2.7-3.9%; 33 studies]. Factors such as infundibular stalk deviation angle, plasma copeptin level, and Knosp grades served as more reliable predictors of postoperative hyponatremia. In contrast, conventional demographic and surgical parameters such as patient age, body mass index, sex, and extent of resection were not consistently identified as significant predictive factors. Secondary analyses revealed that prophylactic fluid restriction significantly reduced the incidence of postoperative hyponatremia from ~ 13.1% to ~ 4.0% (Odds Ratio 3.39 [95% CI; 2.18-5.26, Z = 5.545, P < 0.001]. This meta-analysis establishes definitive 'benchmarks' for anticipated complications after transsphenoidal surgery while highlighting important factors such as prophylactic fluid restriction protocols as a key source of inter-study variability. In addition, this study summarizes the congruence of the predictive factors thought to be influential in leading to postoperative hyponatremia, highlighting key areas of (dis)agreement.