Cardiopulmonary bypass

Open heart surgeries are done under cardiopulmonary bypass support. When an open heart surgery is required, it cannot be done while the heart is full of blood and is beating. Imagine a car has to be repaired. It can't be done without stopping the car. So the heart has to be stopped for open heart surgery. This has to be done without harming the patient, meaning oxygen poor blue blood needs to be enriched with oxygen and red, oxygen rich blood needs to be supplied to the whole body. When the heart is stopped for open heart surgery, this job is done by a heart-lung machine. Blue, oxygen poor blood is collected by the heart lung machine, oxygenated and pumped back to the body during the open heart surgery. Essentially the heart lung machine takes over the function of the lung and the heart for the duration of open heart surgery. This is called cardio-pulmonary bypass.  

Cardiopulmonary bypass carries the risk of blood clots, bleeding , acute kidney injury, and decreased lung and or heart function. Any surgery that requires cardiopulmonary bypass is a major/serious surgery and should not be taken lightly. Nevertheless, open heart surgeries under cardio-pulmonary bypass are necessary and life saving for a large  number of children with congenital heart disease.