Delayed Hyponatremia after Transsphenoidal Surgery for Pituitary Adenomas: A Single Institutional Experience

BACKGROUND: Hyponatremia is a common complication after transsphenoidal surgery (TSS) for pituitary adenomas. This study retrospectively reviewed various clinical factors of pituitary adenoma patients who underwent TSS and aimed to identify possible risk factors of postoperative hyponatremia. METHODS: Total 1,343 patients who underwent TSS for their pituitary adenomas in a single institution were enrolled to this study. We identified and analyzed 93 patients (6.9%) with postoperative hyponatremia and compared them with other 1,250 patients in a control group. Patients' age, sex, tumor extent based on the modified Hardy classification, tumor size and hormonal type of the tumors were analyzed in comparison between two groups. The results of pre- and post-operative combined pituitary function test and their comparison were analyzed to elucidate a possible association between postoperative hyponatremia and hypopituitarism. RESULTS: The onset of postoperative hyponatremia was 7.8 days after surgery (range: postoperative day 3–13). The initial level of serum sodium (Na) level at the start of treatment was 123.5 mmol/L (range: 114–131 mmol/L) and the duration of treatment was 2.7 days (range: 1–9 days). Female predominance was evident in the hyponatremia group (77.4% vs. 61.4%, p=0.02). Preoperative hypopituitarism (58.5% vs. 71.5%, p=0.007) and postoperative hypocortisolism (33.7% vs. 23.4%, p=0.029) were related to postoperative hyponatremia. Other pre- and post-operative clinical factors were not associated with postoperative hyponatremia. CONCLUSION: Postoperative hyponatremia is a common complication after TSS and is potentially fatal. Female patients were more likely to develop delayed hyponatremia. We demonstrated possible associations of delayed postoperative hyponatremia with preoperative and postoperative pituitary functions, but the mechanism behind it should be further investigated.