Concentration of oxygen for an artificial membrane lung and the safety of prolonged extracorporeal membrane oxygenation
Tsuno, K.; Terasaki, H.; Saito, Y.; Sakai, K.; Kishi, Y.; Sakanashi, Y.; Morioka, T.
Masui. Japanese Journal of Anesthesiology 35(10): 1528-1535
1986
ISSN/ISBN: 0021-4892 PMID: 3806943 Document Number: 280009
In order to establish a simple and safe procedure for prolonged ECMO, fundamental studies were done on 12 goats and 3 sheep. The animals were anesthetized only for the cannulation maneuvers, and fed ad lib in a confining cage throughout all the experiments. Blood was withdrawn from the right jugular vein. A veno-arterial bypass with the Kolobow lung and rotary pump was used to return the oxygenated blood into the right carotid artery. The bypass ratio varied from 20 to 50% of the cardiac output of each animal. When the Kolobow lungs with a surface area of 0.8 to 2.5 square meters were ventilated with pure oxygen, the oxygen partial pressure of the outflow blood ranged between 400 to 600 mmHg. Under ECMO with pure oxygen, the physical conditions of the animals gradually declined, and the animals often showed loss of appetite, thrombocytopenia and some neurological disorders, such as nystagmus and convulsions. After 4 to 5 days, the animals became so weak that it was difficult to continue ECMO for more than a week. With the last two goats the concentration of oxygen for the artificial lung was reduced to between 30 to 40% to maintain oxygen partial pressure of the outlet blood at around 100 mmHg. These animals survived prolonged ECMO for 23 and 38 days in good physical condition. When an animal breathes room air and undergoes ECMO with pure oxygen, counterdiffusion supersaturation of blood gases will cause a microbubble formation on the surface of the membrane of the artificial lung. These bubbles may trap platelets, and microaggregates and thrombocytopenia may develop. Oxygen at a high tension will possibly produce excessive superoxide radicals in the blood, and peroxidation of the body tissues may develop. When venoarterial bypass is performed and excessively oxygenated blood flows directly into the brain without mixing with the less oxygenated blood from the natural lung, and without filtration of the microbubbles and platelet aggregates at the lung capillaries, some neurological disorders may develop and prolonged ECMO may lead to a fatal outcome. For a safe prolonged veno-arterial ECMO, the concentration of oxygen to an artificial membrane lung should be controlled to maintain the oxygen partial pressure of the outlet blood at around 100 mmHg.