The effect of remote ischaemic preconditioning on lowering postoperative myocardial troponin I release in children with congenital heart disease undergoing cardiopulmonary bypass.

Support of the circulation during heart surgery using the heart-lung bypass machine is inevitably associated with organ damage and associated reduced function. This is due to reduced blood flow (ischaemia), the effects of restoration of flow (reperfusion injury) and the subsequent inflammation that is caused. The body has its own way of protecting itself against reduced blood flow and oxygen by a mechanism known as preconditioning. In essence, brief periods of mild ischaemia are protective against a subsequent more severe episode of ischaemia. These periods of mild ischaemia can be of the organ itself or of another organ in the body. For example ischaemia of the leg can protect the heart against ischaemia, so called “remote preconditioning”. We have shown in animal and human models that remote preconditioning using a tourniquet placed around the leg for brief periods (similar in duration to when taking blood samples from children) reduces the amount of injury to heart muscle by 50% and also leads to improved heart and lung function. We have shown that remote preconditioning in a similar way protects the organs of a heterogeneous group of children undergoing cardiac surgery, resulting in better function of the heart and lungs and also a reduction of the inflammatory response to the heart-lung machine. This could potentially reduce the problems in looking after children after surgery and also reduce the amount of time spent on the intensive care unit. We intend to study a more uniform group of patients undergoing cardiac surgery in the neonatal period. All interventions will be performed during the period of routine general anaesthesia at the time of surgical repair. We will study the degree of organ injury induced by heart-lung bypass using standard intensive care parameters and equipment for measuring lung function. In addition, the degree heart muscle death and inflammation will be assessed by blood tests. Samples will be taken from indwelling catheters routinely placed at the time of surgery and not require additional venepuncture. Measurements will be made prior to surgery and also at set time intervals in the first 24 hours postoperatively to determine the evolution of effects.