Primary end point The primary end point will be the highest change in serum creatinine from before operation to the first three days postoperatively. Supporting data will be from the highest creatinine and urea in the first three postoperative days. Patients leaving hospital before 3 postoperative days will be included. Good clinical care for patients with renal impairment includes a creatinine measurement on admission and at least one postoperative creatinine measurement. The trial coordinator will oversee this. The data for this study will be from clinically indicated tests. Specific blood tests for this study will not be needed. Data will be collected from the ARMC clinical chemistry results. Data will be stored on computer in a secure are of the ARMC Department of Anaesthesia in line with the Therapeutic Goods Administration Guidelines for Good Clinical Research Practice in Australia.