Inflammatory Response in Patients under Coronary Artery Bypass Grafting Surgery and Clinical Implications: A Review of the Relevance of Dexmedetomidine Use
Figure 1
Overview of a standard extracorporeal circulation system (upper panel) and a detailed view of a heart undergoing artery bypass grafting surgery (lower panel). Cardiopulmonary bypass is achieved by gravity drainage of blood from the vena cava into a reservoir, followed by its pumping through a heat exchanger, oxygenator, and filter, followed by its return to the arterial system, usually the ascending aorta, by means of a centrifugal or roller pump. The heart is excluded from the patient’s circulation by a single venous cannula inserted into the right atrium and advanced into the inferior vena cava, or by dual catheters placed into the superior and inferior vena cava. An aortic cross-clamp is placed between the anterograde cardioplegia catheter and the arterial inflow catheter to separate the heart from the circulation and allow cardioplegic arrest. When the heart is isolated from the circulation, total cardiopulmonary bypass is present, and ventilation of the lungs is no longer necessary to maintain oxygenation. The bypass pump produces nonpulsatile flow into the patient’s aorta by either a centrifugal or roller pump. Myocardial preservation is achieved by decreasing myocardial oxygen consumption by infusing cardioplegia solutions containing potassium into the aortic root, which in the presence of a distally cross-clamped aorta and competent aortic valve ensures diversion of the solution into the coronary arteries. Alternatively, the cardioplegia solution may be administered in retrograde fashion through a cannula placed into the coronary sinus. An additional route for infusion of cardioplegia solutions is directly into newly placed bypass grafts. Cardioplegia solutions may also contain many additives, including blood, insulin, glucose, aspartate, glutamate, calcium, magnesium, nitroglycerine, and superoxide dismutase. None of these additives are definitively better than cold blood cardioplegia with a short cross-clamp time.
