cardiopulmonary bypass

Imagine needing to repair a building’s plumbing while the water still has to keep flowing to every tap — so you reroute the supply through a temporary external pump and filter while you work. Cardiopulmonary bypass does this for the body: a machine temporarily takes over the work of the heart and lungs so a surgeon can operate on a still, bloodless heart.

Blood is drained from the body into a heart-lung machine, where an oxygenator adds oxygen and removes carbon dioxide (the lung’s job) and a pump pushes the blood back into the arteries (the heart’s job). With circulation maintained by the machine, the surgeon can stop the heart and open it or work on its vessels safely. The patient’s blood is kept from clotting in the circuit with heparin throughout.

Cardiopulmonary bypass made open-heart surgery — valve repair, many bypass operations, repair of congenital defects — possible. It is remarkably safe in skilled hands but is not without effects: longer times on the machine carry risks such as inflammation, bleeding, and temporary organ stress, which is one reason some operations are now done off-pump or via catheter techniques.