The modern era of heart surgery began in 1953 after the research efforts of Dr. John Gibbon culminated in the use of the heart-lung machine, also known as cardiopulmonary bypass (CPB). The heart-lung machine temporarily performs the functions of the heart and lungs by circulating blood and exchanging gases, such as oxygen and carbon dioxide. This system creates a temporary interruption of the normal circulation, making heart surgery possible.

During surgery, the heart-lung machine diverts blood from the body and circulates it to the bypass machine where the blood cells pick up oxygen, and blood is filtered, cooled or warmed, and then returned to the body. Because the blood is exposed to artificial filters, tubing, and synthetic surfaces, blood elements are damaged and several physiological reactions can occur.

Research has indicated that during CPB, blood flow to the brain can decrease over time. Consequently, the Duke DREAM Team investigated other interventions that could protect the brain during CPB. We discovered that keeping patients mildly cooler during CPB can help maintain a good blood flow to the brain and keep mechanisms of the brain intact thus protecting the brain during surgery.