Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) involves artificial blood gas exchange. It is primarily administered to patients suffering from severe respiratory or cardiac failure. These cardiopulmonary bypass techniques may be used both during surgery and outside the operating room. Although the introduction of neonatal ECMO once spawned considerable controversy, the methods have become well established. In fact, with portable equipment and percutaneous techniques, ECMO can even be administered during emergency resuscitation subsequent to cardiac arrest. In the future, it is very probably that ECMO will become a regular component of critical care.

The development of extracorporeal membrane oxygenation can be traced back to the early heart-lung machines. During the 1950s, these machines provided patients' blood with oxygen, eliminated carbon dioxide, and provided surgeons with both time and a clear surgical view. In 1953, Gibbon performed the first successful open-heart surgery using his own machine. Moreover, by 1956, Kirklin et al. (cited in Campbell, 1994, pp. 109-116) had documented some 40 cases involving the Gibbon-type pump oxygenator. This device--which employed a roller pump for artificial circulation and heparin for anticoagulation-- eventually became widely used (Campbell, 1994, pp. 109-116). While the early heart-lung machines were effective, they also subjected patients to considerable hemolysis (Levy, O'Rourke, & C

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it adds capacitance to the circuit; (2) it prevents inconsistent venous return; (3) it provides an access site for blood sampling and drug administration; and (4) it traps any air which may become entrained in the circuit's venous limb. From the bladder, blood is pumped by a roller pump through a silicon membrane oxygenator. After passing through this device, the blood is then subjected to a heat exchanger. Ultimately, it reaches the arterial cannula and return to the patient. The silicon membrane oxygenator is a key ECMO component. It essentially consists of a silicon envelope coiled around a spool. The envelope and spool are then encased in a plastic sleeve. The oxygenator's membranes are rated for gas transfer capability. This characteristic--which is a function of surface area--may range from 0.4 m2 for a neonate, to 3.5-4.5 m2 for an adult. As fresh gas flows through the inside of the envelope, patients' blood travels in a countercurrent direction. The gas' composition is typically adjusted in response to patients' arterial blood gases. Patients generally want a Pao2 of 60-100 mm Hg, and a Paco2 30-45 mm Hg. The gas' fraction of inspired oxygen may range from 40 percent to 100 percent. In addition, 1 percent to

Category: Science - E