An oxygenator is a medical device that is capable of exchanging oxygen and carbon dioxide in the blood of human patient in surgical procedures that may necessitate the interruption or cessation of blood flow in the body, a critical organ or great blood vessel. These organs can be the heart, lungs or liver, while the great vessels can be the aorta, pulmonary artery, pulmonary veins or vena cava. An oxygenator is typically utilized by a perfusionist in cardiac surgery in conjunction with the heart-lung machine. However, oxygenators can also be utilized in extracorporeal membrane oxygenation in neonatal intensive care units by nurses.
For most cardiac operations such as coronary artery bypass grafting, the cardiopulmonary bypass is performed using a heart-lung machine (or cardiopulmonary bypass machine). The heart-lung machine serves to replace the work of the heart during the open bypass surgery. The machine replaces both the heart's pumping action and the lungs' gas exchange function. Since the heart is stopped during the operation, this permits the surgeon to operate on a bloodless, stationary heart.
One component of the heart-lung machine is the oxygenator. The oxygenator component serves as the lung, and is designed to expose the blood to oxygen and remove carbon dioxide. It is disposable and contains about 2-4 m² of a membrane permeable to gas but impermeable to blood, in the form of hollow fibers. Blood flows on the outside of the hollow fibers, while oxygen flows in the opposite direction on the inside of the fibers. As the blood passes through the oxygenator, the blood comes into intimate contact with the fine surfaces of the device itself. Gas containing oxygen and medical air is delivered to the interface between the blood and the device, permitting the blood cells to absorb oxygen molecules directly.
Although the renewed attention to blood management is primarily cost-driven, clinicians have long recognized the clinical benefits associated with minimizing the use of donor blood. Transfusions have been linked to many negative outcomes, including the single biggest cause of morbidity and mortality after cardiac surgery - inflammatory response.
A Multi-Strategy Approach
However, reducing transfusions is but one strategy that can be employed to reduce inflammatory response. For decades, surgeons, anesthesiologists and perfusionists have studied the interrelated causes and multiple effects of inflammatory response in attempts to minimize the impact of cardiopulmonary bypass. In addition to reducing transfusions, cardiac teams have documented several additional important strategies:
* Minimizing the blood/foreign surface interface
* Reducing microemboli
* Reducing inflammatory mediators.
Each of these can be addressed, at least partly, through the conduct of cardiopulmonary bypass where the adoption of even a single new technology or technique can create an incremental improvement in the reduction of inflammatory response.