 Code for patient, gender and age. Date and time of admission to ICU Operative procedure and date and time on and off cardiopulmonary bypass Preoperative assessment of left ventricular function, Comorbidities, Pre-, intra- and post-operative medication, Markers of renal function as described above, Doses of frusemide administered or rate of frusemide infusion Use of inotropes or vasopressors Cardiac output whenever measured for clinical purposes in the first 24 hours postoperatively Requirement of renal replacement therapy Urine output in each 6 hour period during the presence of urine catheter Acid base status and electrolytes at baseline, 6 and 24 hours after commencement of cardiopulmonary bypass, Time of intubation and extubation, Date and time of arrival on and discharge from ICU and hospital, death Resources required The principle of the study has been discussed with the involved cardiac anaesthetists, cardiac surgeons, intensivists and intensive care nurses, who have offered their co-operation. ICU research nurse to allocate patients and collect clinical data. Pharmacy will be required to prepare drug and placebo infusion bags. Clinical pathology will be required to perform 24 hour creatinine clearance estimation in addition to those tests clinically indicated Protocol violations All protocol violations will be recorded. It will then be decided whether the nature of such violation had been such that the patient should be excluded from primary data analysis. Such evaluation will be blinded to treatment. 