Cardiopulmonary Bypass Setup and Cannulation

Cardiopulmonary bypass (CPB) is the setup behind almost every open-heart operation. Blood is drained from the right side of the heart, run through the heart-lung machine (pump oxygenator), where it is oxygenated, filtered and warmed or cooled, and then pumped back into the arterial system. With the machine doing the work of the heart and lungs, the heart can be stopped with cardioplegia and the lungs deflated so the surgeon has a still, bloodless field. Extra pump lines run the cardiotomy suckers and the vents, so blood suctioned from the field is returned to the patient instead of lost. The most common setup is central cannulation: an arterial cannula in the ascending aorta and a two-stage venous cannula through the right atrial appendage with its tip in the inferior vena cava. When the right atrium has to be opened (tricuspid repair, atrial septal defect), each vena cava is cannulated and snared with tapes for total bypass. When the ascending aorta is diseased, too short or hidden behind scar from an earlier operation, the femoral artery and vein or the right axillary artery are used instead, and the same femoral technique is used for many minimally invasive and catheter-based heart operations. The patient is fully heparinized before any cannula goes in, and the heparin is reversed with protamine at the end. Going on and coming off bypass is a spoken routine between the surgeon, the perfusionist and the anesthesia provider, and the scrub person is part of it: the right stitch, tourniquet, clamp and cannula must be in hand at each call, and the field must stay ready to go back on bypass until the patient leaves the room. Bypass itself causes an inflammatory reaction, bleeding problems and a risk of tiny air or debris emboli to the brain, and the longer the pump run, the greater the risk to the kidneys, lungs and nervous system. Careful de-airing and steady teamwork lower these risks.