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Objective: Renal dysfunction following cardiac surgery is more apparent in high-risk patients with pre-existing renal dysfunction, diabetes and impaired left-ventricular function, and following complicated procedures involving prolonged cardiopulmonary bypass (CPB). The aim of this prospectively randomised double-blinded placebo-controlled study was to evaluate reno-protective effect of low-dose furosemide infusion in this high-risk group. Methods: Patients with preoperative serum creatinine >130 mmol/l (1.4 mg/dl), left-ventricular ejection fraction <50%, congestive heart failure, diabetes, or procedures involving prolonged CPB were randomised to receive either saline at 2 ml/h (n = 21), or furosemide at 4 mg/h (n = 21). Infusion was commenced after induction of anaesthesia and continued for 12 h postoperatively. Renal dysfunction was defined as >50% increase in serum creatinine postoperatively, or >130 mmol/l (1.4 mg/dl), or requirement for haemodialysis, or all of these. In patients with preoperative serum creatinine >130 mmol/l, >50% increase over preoperative levels was used to define postoperative renal dysfunction. Results: Following cardiac surgery, patients receiving furosemide had a higher urine output (3.4 AE 1.2 ml/kg/h in furosemide group and 1.2 AE 0.5 ml/kg/h in placebo group; p < 0.001), higher postoperative fluid requirement (4631 AE 1359 ml in furosemide group and 3714 AE 807 ml in placebo group, p = 0.011), and lower urinary-creatinine (2 AE 1.3 mmol/l in furosemide group and 5.9 AE 2.5 mmol/l in placebo group p < 0.001). Both groups had significant increase in retinol binding protein/creatinine ratio (7.2 AE 6 to 3152 AE 1411 in furosemide group; 4.9 AE 2.1 to 2809 AE 1125 in placebo group; p < 0.001) and peak serum creatinine (98 AE 33 to 177 AE 123 mmol/l in furosemide group; 96 AE 20 to 143 AE 87 mmol/l in placebo group; p < 0.001), and a significant decrease in peak creatinine-clearance (64.3 AE 29.4 to 39.1 AE 16.6 ml/min in furosemide group; 65.5 AE 38.6 to 41.8 AE 17.8 ml/min in placebo group; p < 0.001) following cardiac surgery, implying significant renal injury following cardiac surgery. Peak creatinine levels (177 AE 123 mmol/l in furosemide group and 143 AE 87 mmol/l in placebo group; p = 0.35) and peak creatinine-clearance (39.1 AE 16.6 ml/min in furosemide group and 41.8 AE 17.8 ml/min in placebo group; p = 0.61) were similar in the two groups. Importantly, there was no difference in incidence of renal dysfunction between the furosemide group (9/21) and the control group (8/21) (relative risk 1.1, 95% confidence interval 0.6-2.2; p = 0.99). Conclusions: Our randomised trial did not demonstrate any benefit of furosemideinfusion postoperatively in high-risk cardiac surgical patients. Although urinary output increased with furosemide, there was no decrease in renal injury, and no decrease in incidence of renal dysfunction. #

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