Frusemide Infusion for the Prevention of Deterioration in Renal Function Post Cardiac Surgery.

All patients will receive standard supportive care based on current established management practice of cardio-thoracic patients. The only difference in treatment will be the randomisation of patients to receive/not receive protocolised administration of frusemide targeting a urine output. There will be 2 groups of patients. The control group-which will receive frusemide bolus doses if required as determined by the surgeon/consultant physician. The frusemide infusion group-which will be monitored to achieve a trial specified hourly urine output target range of 1-2mls/kg/hour. In order to achieve this target the patient may need to receive a loading dose of frusemide and may also then require a frusemide infusion. The aim will be to maintain the urine output within the target range for the first 48 hours after cardiac surgery.