cardiopulmonary bypass and cardioplegia

Extracorporeal circulation and cardiopulmonary bypass are synonymous terms denoting a method by which the blood that usually returns directly to the heart is temporarily drained from the superior and inferior venae cavae. The blood is diverted into a reservoir, where it is oxygenated and subsequently returned to the patient’s arterial circulation. This process effectually excludes the heart from the general circulation and leaves it empty so that it can accommodate surgical intervention.

Myocardial protection

To provide a dry, motionless, operative area, a cross-clamp is placed across the ascending aorta above the coronary ostia and proximal to the aortic cannula, thus isolating the coronary circulation and preventing blood entering the chambers of the heart. Therefore, techniques of myocardial protection are used to preserve myocardial function and prevent cell death. Cardioplegic techniques for myocardial protection involve the delivery of cardioplegic solution to the myocardium to provide diastolic electromechanical arrest. This is administered by an anterograde approach via the aortic root or direct coronary ostium access, or by a retrograde manner if severe coronary artery occlusions exist. The latter may not provide adequate right-heart protection; thus, the delivery of both anterograde and retrograde cardioplegia may ensure adequate distribution and subsequent improved myocardial protect. Intermittent cardioplegia delivery (i.e. every 15–30 min) allows a relatively bloodless surgical view during more challenging operative periods. Continuous administration would improve for myocardial protection but this is not always practical.
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