Plasma sodium and potassium concentrations after hypophysectomy in dogs with corticotroph adenomas

Background: Electrolyte abnormalities, especially hypernatremia, are frequent complications after transsphenoidal hypophysectomy in dogs with pituitary-dependent hypercortisolism. Objectives: To describe electrolyte abnormalities after transsphenoidal hypophysectomy and to investigate possible associations between postoperative hypernatremia and clinical and surgical variables as well as with postoperative outcome. Animals: One hundred and twenty-seven client-owned dogs. Methods: Dogs with pituitary corticotroph adenomas that underwent transsphenoidal hypophysectomy were retrospectively included. Plasma sodium and potassium concentrations were measured −2, +2, +8, +24, and +48 hours from hypophysectomy. Clinical (breed, age, body weight, skull type, urinary cortisol/creatinine ratio, percentage of suppression to dexamethasone) and surgical variables (duration of anesthesia and surgery, pituitary dimensions) were compared to the development of hypernatremia. Results: Postoperative hypernatremia developed in 46.5% (57/127) of dogs and hyponatremia in 6.3% (8/127). Plasma sodium concentration increased after surgery and peaked at 8 hours after surgery, normalizing after 24 to 48 hours. Plasma potassium concentration increased without exceeding the reference limit. No significant associations were found between clinical and surgical variables and hypernatremia, or between hypernatremia and postoperative death, long-term survival or recurrence. Surgery time was significantly longer in dogs that developed persistent diabetes insipidus (P =.02) and persistent diabetes insipidus occurred more frequently in dogs with enlarged pituitary glands (P =.01). Conclusion and Clinical Importance: Hypernatremia remains a frequent postoperative complication after transsphenoidal hypophysectomy but did not appear to have an impact on postoperative outcome. No predisposing factor to postoperative hypernatremia was identified. Variations in plasma potassium concentrations do not seem to influence postoperative outcome.