Cardiopulmonary bypass (CPB) has developed into an invaluable tool for operations on the thoracic viscera. By interfacing with the cardiovascular system, total CPB completely replaces the function of the heart and lungs for a short time. Modifications of CPB have been designed to partially replace or control more specific aspects of the cardiopulmonary systems. To fully utilize the tremendous flexibility available with “the pump,” one must understand its components, operation, and potential for complications.
The development of CPB is a testament to personal perseverance and collaboration and demonstrates how cardiac surgery has truly evolved as a science. Initial progress in the field of extracorporeal circulation required mastery of the principles of total-body oxygen delivery and consumption. Later, further refinements in the understanding of metabolic demands at the cellular level served to enhance the safety and flexibility of circulatory support. Undoubtedly the most important milestone in the development of CPB is John Gibbon’s use of the first clinical application of CPB. In 1953, after devoting most of his career to this work, he successfully repaired an atrial septal defect in a young woman with a pump-oxygenator. Additional milestones include the work of Bigelow, who, in the early 1950s, reported on systemic hypothermia with topical cooling as a means to reduce oxygen demand during the periods of reduced oxygen delivery inevitably encountered during operations on the heart. Shortly thereafter, Lillehei began performing congenital repairs using “cross circulation,” employing a parent’s cardiopulmonary system to support a child’s during cardiac surgery. Finally, in the mid-1950s, Kirklin and colleagues at the Mayo Clinic ushered in the era of routine congenital repairs using the Mayo–Gibbon pump-oxygenator. Modern refinements in equipment and techniques have subsequently evolved as a consequence of the proliferation of coronary revascularization surgery and increased industrial interest.
Components of the CPB Circuit
Current-generation CPB circuits maintain much of the simplicity of older perfusion equipment but have much more flexibility and ability to more precisely control various perfusion parameters. Core components of any circuit include cannulas, tubing, a pump, and an oxygenator (Fig. 24-1). In reality, however, even basic circuits used in routine clinical practice include many other features such as additional pump heads for suction, venting of the heart, and delivery of cardioplegia. Venous reservoirs are also needed to maintain adequate circuit volume and remove air. Filters are required at various levels to prevent embolic complications. Finally, a heat exchanger facilitates systemic and myocardial cooling and rewarming.
Schematic of typical CPB circuit. (Reprinted with permission from Cohn LH, Edmunds LD Jr (eds). Cardiac Surgery in the Adult, 2nd ed. New York: McGraw-Hill, 2003.)
Cannulation for CBP is typically performed centrally with an inflow cannula in the ascending aorta ...