The pericardium is incised anteriorly (and laterally on the diaphragmatic surface) exposing the heart. The pericardial well is created by securing the pericardial edges to the retractor or skin with sutures. Digital palpation is notoriously inaccurate in detecting atherosclerotic disease. It is our preference that epiaortic echo be completed on all patients to better detect atherosclerotic plaque and thus minimize embolic phenomenon. If disease is detected, alternate sites for cannulation (proximal arch, right axillary or femoral artery) may be chosen (Fig. 25.2).

If the disease is diffuse and the cross-clamp cannot be applied safely, the procedure can be performed either off-pump or on-pump beating heart, minimizing aortic manipulation.

Two concentric purse-string sutures are placed in the aorta at the site of cannulation. Care must be taken to place these sutures into the media of the aorta to avoid hematoma formation. The aorta is incised and the appropriately sized cannula is inserted and secured. The cannula is de-aired and connected to arterial inflow line. Typically, a purse-string suture is placed in the right atrium and a dual- or triple-staged venous cannula is placed with the tip extending into the IVC. Independent cannulation of the SVC and IVC is sometimes used to improve venous drainage and prevent RV injury due to exposure to systemic temperatures during cardioplegic arrest. This may also be necessary to provide adequate drainage if the heart is to be displaced into the right chest to expose the proximal circumflex marginal or the circumflex proper. Once this is completed CPB is initiated. CPB initiation is a critical event requiring the full attention of the surgeon, anesthesiologist, and perfusionist. It is essential that arterial inflow is proven to be unobstructed before venous drainage is freely allowed, which otherwise could result in exsanguination. Issues with arterial inflow due to cannula malposition, aortic dissection, or even an overlooked tubing clamp must be assessed and corrected. Once CPB is safely established, ventilation is stopped and the patient cooled (our preference is cooling to 32° to 34°C for most CABG patients). If a PA catheter has been placed, it must be withdrawn into the main PA before the ventilator is discontinued, to avoid the frequently fatal complication of PA catheter pulmonary vascular injury. This injury risk is increased with more profound hypothermia that stiffens the catheter.

Inadequate venous drainage must be corrected to avoid hypoxia through continued ejection of both right and left ventricles, with systemic oxygen desaturation by admixture of blood traversing the unventilated lungs. Additionally, elevated central venous pressure associated with poor venous drainage decreases the transcerebral pressure gradient. Inadequate venous return is often associated with the reduced arterial inflow (and arterial pressure) which can further reduce the pressure gradient placing the patient at risk for cerebral hypoperfusion and injury.

Once full cardiopulmonary bypass is achieved and the heart is decompressed, the coronary targets are evaluated. Most of the targets for revascularization can be easily identified
by visual inspection and gentle palpation to ensure that there is minimal or no atherosclerotic disease at each proposed site. These sites and the visible coronary anatomy are compared to the angiogram, which must be available in the operating room.