Cardiopulmonary-bypass and Reno-protective Effect of Atorvastatin Trial

Overview

Acute kidney dysfunction is common after cardiac surgery. While many patients suffer no long-term ill effects from post-operative kidney dysfunction, some require initiation of dialysis therapy that can contribute to long-term morbidity. Further, there is evidence to suggest that those patients requiring dialysis after cardiac surgery have a higher risk of death in hospital. The exact reasons why some patients develop acute kidney dysfunction after cardiac surgery is not well understood. However, research evidence to date has suggested that the presence of co-morbid illnesses (i.e., diabetes mellitus) and exposure to cardiopulmonary bypass (heart-lung machine used during operation when heart is stopped). Cardiopulmonary bypass, in particular, has been shown to over-activate several aspect of the body's immune system. Such over-activity can induce oxidative stress and contribute to acute kidney dysfunction. The investigators believe that the statin drug, atorvastatin, might reduce the oxidative stress that occurs during cardiopulmonary bypass, and thus, prevent or reduce the magnitude of acute kidney dysfunction in those patients at highest risk. The investigators hope to give atorvastatin (40 mg orally) to patients immediately prior to and for 3 days after cardiac surgery, and to compare the effects on kidney function with patients who have not had atorvastatin. Atorvastatin is the most commonly prescribed medication in Australia and is used to reduce blood cholesterol levels and decrease the risk of heart attacks and stroke. Recently, however, it has been discovered that atorvastatin may be useful for prevention of inflammation and oxidative stress in other conditions, such as following cardiac surgery with cardiopulmonary bypass. Thus, the investigators plan to examine whether atorvastatin can prevent acute kidney dysfunction. This trial as planned is a pilot study. If atorvastatin shows promising evidence of reduction in acute kidney dysfunction, further studies on a larger scale would be required to justify its general use. The investigators plan to determine whether atorvastatin, a statin drug, possesses kidney protective effects in patients at risk for perioperative acute kidney dysfunction after cardiac surgery and exposure to cardiopulmonary bypass. This is a pilot, randomized, blinded, placebo-controlled trial. The investigators plan to administer atorvastatin (40 mg orally) or placebo to patients immediately prior to and for 3 days after cardiac surgery. The atorvastatin/placebo will be given orally either by orogastric tube after induction of anaesthesia or swallowed by the patients. Whether a particular patient receives the atorvastatin or placebo will be decided at random, and neither the patient nor the investigators will be aware of the allocated treatment. The investigators plan to measure kidney function before and after cardiac surgery using the standard blood tests. The investigators also plan to measure markers of inflammation and oxidative stress in the blood. This may give insight into the mechanisms whereby atorvastatin exerts its effects. The investigators will also take four 20 ml samples of blood, spaced before, and after the operation, from the arterial catheter routinely inserted in every patient undergoing cardiac surgery. The investigators believe that there will be no significant additional risk to a patient who participates in the study, and no discomfort other than that normally associated with cardiac surgery. Informed consent will be obtained from the patient prior to the operation by one of the investigators or the ICU research nurse. The clinical care of a patient who does not consent for any reason will not be affected.