Effects of Low-Dose Tolvaptan for Fluid Management After Cardiovascular Surgery

Background: Perioperative management of body fluid levels after cardiovascular surgery with cardiopulmonary bypass is essential. Fluid management using tolvaptan with conventional diuretics is effective in maintaining urine output without worsening renal function. This study aimed to improve the in-out balance in the early perioperative phase using low-dose tolvaptan (3.75 mg/day). Methods and Results: This prospective, single-center, randomized, open-label study included 199 patients who underwent cardiovascular surgery with cardiopulmonary bypass in Kobe City Medical Center General Hospital between September 2018 and December 2020. Treatment with tolvaptan and loop diuretics (tolvaptan group; 99 patients) was compared with treatment with loop diuretics alone (control group; 100 patients) to evaluate achievement of preoperative body weight as the primary outcome. Secondary outcomes were urine volume, the incidence of worsening renal function (WRF), and postoperative paroxysmal atrial fibrillation (POAF). There was no significant difference between groups in the return to preoperative body weight on postoperative Day 6. The tolvaptan group had significantly increased urine volume (2,530 vs. 2,150 mL/day) and decreased total furosemide dose (24 vs. 32 mg) compared with the control group. No significant differences were observed in the development of WRF and POAF between the 2 groups. Conclusions: Although low-dose tolvaptan administration did not shorten the time to achieving preoperative body weight, it did significantly increase urine volume without WRF and POAF.