ISOLATED HYPONATREMIA AFTER TRANSSPHENOIDAL PITUITARY SURGERY

A retrospective analysis was performed to study the fluid and sodium s tatus of patients undergoing transsphenoidal surgery (TS) for Cushing' s disease. We evaluated the time of onset, duration, and relative inci dence of isolated hyponatremia and identified possible factors associa ted with it. Of 58 patients that underwent TS over 1 yr, 52 without po stoperative diabetes insipidus or Volume depletion were studied. Isola ted hyponatremia after TS for Cushing's disease occurred in 21%, and s ymptomatic hyponatremia (plasma sodium, less than or equal to 125 mmol /L) with new onset headache, nausea, and emesis occurred in 7.0% of al l operated. These later patients escaped monitoring and intervention f or 24 h. The development of hyponatremia began early in the postoperat ive period and progressed slowly over 7 days. Maximum antidiuresis occ urred on postoperative day 7. Vasopressin levels measured in two patie nts while hypoosmolar suggested that unregulated vasopressin release c ontributed to the hyponatremia. Cortisol levels, glucocorticoid replac ement, and pituitary adenoma size were similar in normonatremic and hy ponatremic patients. Patients combining a history of an estrogenic mil ieu and documented posterior pituitary trauma at surgery experienced l ower nadir plasma sodium. All hyponatremic patients were fluid restric ted, and none developed progressive neurological symptoms, morbidity, or mortality. We speculate that the mild degree and slow rate of devel opment of hyponatremia and/or active monitoring and intervention contr ibuted to the good outcome.