CTNI-34. A RANDOMIZED PROSPECTIVE TRIAL OF POST-OPERATIVE FLUID RESTRICTION TO DECREASE THE INCIDENCE OF DELAYED HYPONATREMIA AND READMISSION AFTER TRANSSPHENOIDAL SURGERY

Abstract BACKGROUND Delayed hyponatremia (hypoNa) is the leading cause of readmission following transsphenoidal surgery (TSS). Some institutions have adopted post-operative fluid restriction (FR) protocols based on retrospective studies. We present results of a prospective randomized controlled trial evaluating post-TSS FR. METHODS 300 participants scheduled for TSS (2016-2023) at a single institution were included. Patients with CKD, CHF, AVP deficiency on postoperative day (POD) 3, chronic hypoNa, untreated adrenal insufficiency/hypothyroidism, and those for whom FR was felt unsafe were excluded. Patients were randomly assigned to control (CON, n=94) or moderate FR (FR1, n=39). Participants in CON group were instructed to drink ad lib. Participants in FR1 were FR to 1.8 liters/day (2 liters/day if > 100 kg) from POD3-14. Based on interim analysis suggesting a trend toward reduced hypoNA, FR was changed to strict FR (FR2, n=62) of 1 liter/day (1.2 liters/day if > 100 kg). Serum sodium (Na) was monitored inpatient and on POD 3, 7, 10, and 14, and readmissions evaluated. Fluid intake and thirst were assessed. RESULTS In the intention-to-treat analysis, incidence of hypoNa (Na < 135 mEq/L) was 31.9% CON, 28.2% FR1, and 21% FR2, and severe hypoNa (Na < 125 mEq/L) 7.4% CON, 5.1% n FR1 and 0% FR2. Readmission for hypoNa occurred in 6.4% (n=6) CON, 7.7% (n=3) FR1 and 1.6% (n=1) FR2. Severe hypoNa occurred more frequently in CON vs. FR2 (P=0.04), and nadir Na was higher in FR2 vs. CON (P=0.02). Although thirst scores were similar among groups, an individual’s thirst score correlated with compliance CONCLUSION Results of this randomized study show a reduction in severe hypoNa and readmission for hypoNa in patients on FR from POD3-14 after TSS vs. patients instructed to drink ad lib. This provides strong evidence that post-TSS FR decreases rate of delayed hypoNa and related readmission.