61: Cardiopulmonary Bypass in the Pediatric Patient

The development of cardiopulmonary bypass (CPB) has enabled operative treatment for countless numbers of patients with a multitude of acquired and congenital cardiac and vascular anomalies. The CPB circuit is a unique device designed to divert a patient’s circulation around the area that requires surgical repair so that surgeons can operate in a virtually bloodless field. The typical CPB circuit consists of a series of blood pumps that provide cardiopulmonary support through disposable components consisting primarily of tubing, a blood collection reservoir, and an oxygenator (Fig. 61-1). The deoxygenated venous blood is pumped through the oxygenator and is returned to the arterial system of the patient. The first successful open heart surgical procedure using an extracorporeal CPB machine was performed in 1953 by John Gibbon.¹ Since then, there have been dramatic improvements to the device itself, to the components required for its application and to the techniques and strategies used to apply it, and to the monitoring, while safety systems have been designed to enable safe and consistent results, with steadily improving patient outcomes. This chapter will provide a general overview of the CPB circuit components [extracorporeal circuit (ECC)] and a brief discussion of strategies used to apply this technology in the field of pediatric cardiac surgery.

Circuit Components

Venous Cannulae

Deoxygenated blood is diverted from the systemic atrium to the collection reservoir via a venous cannula. Although CPB can be simply established using a single venous cannula placed in the right atrium, most pediatric operations require direct or indirect (via the right atrium) systemic (or bicaval) venous cannulation. As the situation warrants, venous drainage may be achieved through peripheral cannulation of one or more of the large peripheral veins. This is particularly true for larger children, in which femoral vessels might be sizeable. For smaller children and infants presternotomy cannulation of the internal jugular vein in the case of a truly hostile mediastinum might be an option for venous drainage. The diameter of the venous cannula/e depends on the size of the patient, the number of cannulae, and the desired CPB blood flow rates for the particular child and operation. Venous drainage is normally facilitated by gravity, but may be assisted by adding low-level vacuum, allowing in turn for the use of smaller venous cannulae. The vacuum is applied to the venous reservoir in the circuit, and should not exceed a negative pressure of 40 mm Hg. The potential drawback for vacuum assisted venous drainage is air entrainment and hemolysis through excess negative pressure; when applied appropriately, this risk of such complications is nevertheless minimal.^2,3

Tubing