Prevention of Delayed Hyponatremia Following Transsphenoidal Surgery for Pituitary Mass in Patients with and Without Diabetes Insipidus

Introduction: Hyponatremia due to the syndrome of inappropriate ADH (SIADH) is a common complication of transsphenoidal surgery (TSS) and the leading cause of readmission. A protocolized approach to early recognition and treatment of hyponatremia is crucial to prevent complications. We describe our institution’s historical approach to identification and management of hyponatremia after TSS.

Methods: All patients who underwent TSS at the University of Pennsylvania Health System between January 1, 2015 and January 31, 2020 were identified. Patients without post-operative day (POD) 7 sodium values were excluded. Patient demographics, tumor characteristics, and clinical course, including routine POD 7 sodium value, and hospital readmissions were recorded. SIADH was defined as a serum sodium < 135 mmol/L within 14 days of TSS, in absence of other causes.

Hyponatremia prevention and identification protocol included pre and post-operative education on symptoms of hyponatremia, counseling patients to drink only to thirst, and routine measurement of sodium and urine osmolarity on POD 7. Fluid restriction was instituted when hyponatremia developed.

Results: 357 patients underwent TSS and met eligibility criteria. Mean pituitary tumor size was 21.6 mm. 13.5% patients developed post-op SIADH after discharge. Among outpatients who developed SIADH, 82% were identified on POD 7 labs. 25% patients with delayed hyponatremia required readmission. 20% outpatients with hyponatremia experienced preceding DI.

Conclusion : Our structured protocol was effective in identifying most outpatients with delayed hyponatremia. However, a substantial number of patients still required hospital readmission. Pre-emptive fluid restriction is a recently recognized tool for reducing rates of hyponatremia and readmission, and can be integrated into post-op management pathways. At our institution, we recently adopted pre-emptive 1-liter fluid restriction on POD 4-8. Comparison of the rate of delayed hyponatremia in patients treated with pre-emptive fluid restriction with those counseled to drink to thirst is needed to determine the value of early fluid restriction.