OBJECTIVES One of the most significant complications seen after the maze procedure for atrial fibrillation is excessive fluid retention, with subsequent pulmonary complications. To address this problem we recently started treating all patients prophylactically with a continuous infusion of furosemide starting immediately after the operation. METHODS Seventy-five consecutive patients with statistically similar demographic characteristics were divided into two groups. In the continuous infusion group (n = 36) furosemide was given intravenously as a continuous infusion at a dose of 2 to 15 mg/h for the first 48 hours after the operation, and in the bolus dose group (n = 39) furosemide was administered in bolus doses (50-100 mg) to maintain a targeted daily urinary output of 25 to 50 mL/kg. Hemodynamic data, urinary output, fluid balance, daily weights, and pulmonary complications were recorded during the first 48 hours after the operation. RESULTS The mean postoperative urinary output was higher, the total furosemide dose was lower, and the pulmonary complications were fewer in the continuous infusion group than in the bolus dose group. Three patients in the bolus dose group were reintubated after the operation, whereas none in the continuous infusion group were reintubated. Supplemental oxygen requirements were greater in the bolus dose group (7 vs 4 patients, P <.05). In the bolus dose group, 4 patients (10%) required thoracentesis and 3 patients (8%) required chest tube insertions for postoperative pleural effusions, in contrast with 1 patient (3%) each in the continuous infusion group (P <.05). CONCLUSION Despite a smaller total dose relative to bolus infusion, prophylactic continuous furosemide infusion decreased the adverse pulmonary complications associated with excessive fluid retention in patients undergoing the maze procedure for atrial fibrillation.