Cardiopulmonary bypass CPB or heart-lung machine , also called the pump or CPB pump , is a machine that temporarily takes over the function of the heart and lungs during open-heart surgery by maintaining the circulation of blood and oxygen throughout the body. CPB is operated by a perfusionist. The machine mechanically circulates and oxygenates blood throughout the patient's body while bypassing the heart and lungs allowing the surgeon to work in a bloodless surgical field. CPB is commonly used in operations or surgical procedures involving the heart.
The technique allows the surgical team to oxygenate and circulate the patient's blood, thus allowing the surgeon to operate safely on the heart. In many operations, such as coronary artery bypass grafting CABG , the heart is arrested , due to the degree of the difficulty of operating on a beating heart. Operations requiring the opening of the chambers of the heart, for example mitral valve repair or replacement , requires the use of CPB.
This is to avoid engulfing air systemically, and to provide a bloodless field to increase visibility for the surgeon. The machine pumps the blood and, using an oxygenator, allows red blood cells to pick up oxygen, as well as allowing carbon dioxide levels to decrease.
This mimics the function of the heart and the lungs, respectively. CPB can be used for the induction of total body hypothermia , a state in which the body can be maintained for up to 45 minutes without perfusion blood flow. If blood flow is stopped at normal body temperature , permanent brain damage can occur in three to four minutes β death may follow. Similarly, CPB can be used to rewarm individuals who have hypothermia. The blood is cooled during CPB and is returned to the body.
The cooled blood slows the body's basal metabolic rate, decreasing its demand for oxygen. Cooled blood usually has a higher viscosity, but the various crystalloid or colloidal solutions that are used to prime the bypass tubing serve to dilute the blood. Maintaining appropriate blood pressure for organs is a challenge, but it is monitored carefully during the procedure.
