Since its first use in humans in 1955, the heart-lung machine has been used in millions of open-heart surgeries. Nevertheless, there are risks associated with use of the machine. The complication rate is between 1 and 4 percent, depending on the kind of surgery.

The major risks associated with the heart-lung machine include:

• Blood clots. These may form as the machine processes blood and in extreme cases may cause stroke, heart attack or kidney failure upon return to the body’s bloodstream.
  
  
• Postpericardiotomy syndrome. A severe inflammatory response that may damage many of the body’s systems and organs.
  
  
• The reintroduction of fat and debris from the surgical field through the use of suction.
  
  
• Cardiac arrest.

Problems with temporary confusion or memory loss have also been reported in some cases. To avoid these risks, new surgical techniques called beating heart (or off-pump) surgeries have been developed, in which the heart beats throughout the operation and the heart-lung machine is not used. Some types of beating heart surgery are minimally invasive, requiring only small incisions. Other versions involve opening the chest. Today, about 25 percent of coronary artery bypass surgeries are performed without use of the heart-lung machine.