PMON47 Fluid restriction reduces hyponatremia and hospital readmission rates following pituitary surgery

: Rationale: Hyponatremia occurs in approximately 20% of patients after transsphenoidal pituitary surgery (TSS). Symptomatic delayed hyponatremia from SIADH is a major cause of morbidity and hospital readmission. Prophylactic fluid restriction (FR) protocols starting 2-5 days after surgery may potentially reduce rates of symptomatic hyponatremia and readmissions. METHODS: Patients who underwent TSS for sellar and parasellar masses at a tertiary referral center were discharged with a one-liter fluid restriction protocol. Serum sodium levels were measured on post-operative day (POD) 7 with telephone follow-up care. Rates of hyponatremia and readmissions were compared to a cohort of 316 post-operative patients treated prior to the protocol. Numerical variables were summarized as mean ± SD and significance testing calculated by Chi-square and t-test. RESULTS: 105 patients were enrolled on the FR protocol upon discharge. Twelve patients were excluded as they had diabetes insipidus or prolonged hospitalization beyond POD 7. Ninety-three patients were included in the analysis, of whom 74.3% had pituitary adenomas, 5.4% Rathke's Cleft cysts, 8.6% meningiomas, 5.4% apoplexy, 2.2% craniopharyngiomas, and 4.3% other masses. Hyponatremia occurred in 13/93 (14%) patients. Mean POD 7 sodium was 137.9 mmol/L across the entire cohort. Two patients (2.1%) were readmitted for hyponatremia, while 3 were re-admitted for other causes. 88/93 (94.6%) of patients complied with the FR protocol. Of the 5 non-compliant patients, 2 developed hyponatremias (40%) compared to 3/88 (3.4%) in those who complied (p=0.008). Mean POD7 sodium was 138 (+/-4.5) mmol/L in those that complied and 135 (+/- 4.7) mmol/L in those who did not. Overall readmission rate for those with postoperative hyponatremia was 23% compared to 2.5% for those with normal sodium levels (p=0.0023). 15.4% of patients with hyponatremia were re-admitted for hyponatremia treatment, compared to 0/80 (0%) of those who did not develop post-operative hyponatremia (p=0.0004). Age and BMI did not impact hyponatremia rates. In 316 patients treated in 2012-2018 prior to the FR protocol, 78 (24.7%) developed delayed hyponatremia with 6% readmitted for hyponatremia. Thirty nine percent of patients with delayed hyponatremia were re-admitted, compared to 7.6% for those without hyponatremia. Compared to patients not on FR, patients on the FR protocol had 50% reduced risk of hyponatremia (OR=0.49 (95% CI 0.26-0.94, p=0.03), and a 3-fold reduced risk of overall readmissions (OR=0.31; 95% CI 0.12-0.81, p=0.0157) and readmission for hyponatremia (OR= 0.34;95% CI 0.08-1.5, p=0.16). A post-operative CSF leak or use of a lumbar drain were associated with an increased readmission rate in the historical cohort. CONCLUSION: Instituting a one-liter daily FR protocol in patients after TSS results in significantly reduced rates of hyponatremia, overall readmissions, and readmission for symptomatic hyponatremia. A FR protocol should become routine practice in the post-operative care of patients undergoing pituitary surgery. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.