• In early 1950s first open heat procedures were performed under
  • Cooling an circulatory arrest
  • Cross circulation between parent and child
  • Cardiopulmonary bypass with pump and oxygenator

Components of cardiopulmonary bypass circuit

• Cannula is inserted into right atrium to drain venous return
• Venous blood passes into venous reservoir under gravity
• Oxygenated (and CO₂) removed usually by membrane oxygenator
• Heat exchanger control blood temperature
• Surgery often performed with 5-10 C of hypothermia
• A 40 mm filter removes air bubbles
• Pump returns blood into aorta distal to a cross clamp
• Suction used to remove blood from operative field
• Returned to patient via cardiotomy reservoir

Picture provided by Phillip Endelmann, University of Innsbruck Medical School, Austria

Complications of bypass

• Prolonged bypass induces cytokine activation and an inflammatory response
• Results in:
  • Red cell damage and haemoglobinuria
  • Thrombocytopenia
  • Clotting abnormalities
  • Reduced pulmonary gas exchange
  • Cerebrovascular accidents

Bibliography

Levy J H,  Tanaka K A.  Inflammatory response to cardiopulmonary bypass.  Ann Thorac Surg 2003;  75:  S715-720.

Merrill W H.  What's new in cardiac surgery.  J Am Coll Surg 2002;  194:  617-635.

Wheatley D J.  Coronary artery surgery at the dawn of the 21st Century.  J R Coll Surg Ed 2002;  47:  608-12.