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Background and study aims Open-heart surgery is carried out on more than 35,000 UK patients each year. Currently only 3-4% die in the period immediately after surgery. However, the numbers of patients experiencing respiratory complications is much higher and is rising due to the increasing number of high-risk patients having open-heart surgery. Complications after surgery can be life threatening, place an enormous burden on hospital resources and are associated with increased NHS costs. Conventional open-heart surgery requires the use of the heart-lung machine, also known as cardiopulmonary bypass (CPB), for 1-2 hours or more depending on the complexity of the operation. During this time the heart is stopped and most of the blood supply is diverted from the heart and lungs to allow the operation to proceed in a largely blood-free environment. These steps of diverting the blood supply from the heart and lungs, stopping the heart and artificially deflating the lungs are thought to be associated with injury to the heart and lungs, inflammation and major complications. Over the years, effective techniques have been developed to protect the heart from this injury. These involve feeding the heart with an artificial intermittent supply of blood containing protective chemicals. However, no methods for protecting the lungs have been developed. The lungs are allowed to deflate, and remain deflated with a limited blood supply for the entire period when the heart-lung machine is being used. The aim of this study is to investigate a simple strategy to protect the lungs during cardiac surgery. It involves inflating and deflating the lungs several times a minute for the entire period when the heart-lung machine is being used. We think that this treatment may reduce the risk of an injury to the lungs. This procedure has been tested and validated by our group in large animal experiments and is also being evaluated in a similar trial on safety and feasibility at the Bristol Heart Institute. We propose to compare the strategy of inflating and deflating the lungs when the heart-lung machine is being used with the current standard practice of allowing the lungs to deflate, focusing in particular on the effects of the two strategies on markers of inflammation in the lungs and peripheral blood. Who can participate? Patients having elective or urgent coronary artery bypass grafting surgery (CABG) using the heart-lung machine and with the heart stopped. What does the study involve? General anaesthesia will be used in the same way for all participants. Patients who give written consent to take part will be assigned by chance (like tossing a coin) to have the operation done in one of two ways: low-frequency ventilation or conventional treatment. In the low-frequency ventilation group, the anaesthetist will inflate and deflate the lungs several times a minute when the heart-lung machine is being used. If the inflated lungs interfere with the surgeon’s ability to operate on the heart, the lungs will be deflated for as long as is necessary. Then, the anaesthetist starts to inflate and deflate the lungs again. In the conventional treatment group, the anaesthetist will disconnect the lungs from the ventilator. The lungs will be allowed to deflate and remain deflated when the heart-lung machine is being used. Post-operative management will be carried out in the usual way and be the same for all participants, irrespective of the way in which the lungs were treated when the heart-lung machine was being used. What are the possible benefits and risks of participating? If we are right in thinking that inflating and deflating the lungs is beneficial, patients treated in this way when the heart-lung machine is being used will be less likely to have a lung injury. However, we do not know that this will happen. It is possible that patients treated conventionally may do better. We can only find out which treatment will benefit patients most by doing the study. We do not expect patients to be at higher risk. In particular, we do not expect patients having the treatment which involves inflating and deflating the lungs to have any additional pain, discomfort, distress or changes to lifestyle compared to patients who have conventional treatment. We will ask all participants to donate some blood while they are in hospital and to do some extra tests to measure how well their lungs are working. Doing these tests may be quite painful because of the chest wound after the operation. However, the tests do not cause any harm and the pain will stop after doing the test. Where is the study run from? The study will be run by doctors and researchers at the Hammersmith Hospital where cardiac surgery operations are carried out. When is the study starting and how long is it expected to run for? The study is expected to start in June 2012 and it is expected to run for 2 years. Who is funding the study? British Heart Foundation (UK) Who is the main contact? Professor Gianni Angelini [email protected]

Inclusion criteria

• Open-heart surgery with CPB / coronary artery bypass grafting (CABG)

Links

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