Cardiopulmonary Bypass and the Anesthesiologist

The cardiopulmonary bypass (CPB) circuit is designed to perform four major functions: (1) oxygenation and carbon dioxide elimination, (2) circulation of blood, (3) systemic cooling and rewarming, and (4) diversion of blood from the heart to provide a bloodless surgical field. Typically, venous blood is drained by gravity from the right side of the heart into a reservoir that serves as a large mixing chamber for all blood return, additional fluids, and drugs. Because (in most instances) negative pressure is not employed, the amount of venous drainage is determined by the central venous pressure, the column height between the patient and reservoir, and resistance to flow in the venous circuitry. Venous return may be decreased deliberately (as is done when restoring the patient’s blood volume before coming off bypass) by application of a venous clamp. From the reservoir, blood is pumped to an oxygenator and heat exchanger unit before passing through an arterial filter and returning to the patient. Additional components Goals and Mechanics of Cardiopulmonary Bypass