Cardiopulmonary function during and after prolonged extracorporeal circulation with membrane oxygenators in dogs

Prolonged veno-arterial partial extracorporeal circulation using membrane oxygenator was performed in 19 alert dogs. Investigations of alterations in the corpuscular elements of the blood during the perfusion showed 89 mg% as the highest value of free haemoglobin. A significant decrease in the platelet count during the first two hours of bypass to a value of about 100 000/mm3 was found. Measurements of lung and heart functions did not reveal any significant differences between the baseline values and those obtained after 24 hours' bypass and again after three months' observation. Microscopic examination of the lungs and hearts only showed moderate focal alveolar oedema in the dogs killed immediately after 24 hours' bypass. These alterations could be explained as a consequence of the extracorporeal circulation. No changes were found at the microscopic examination of the lungs and hearts three months later. By haemodilution technique, the dogs suffered from severe universal oedema after a few hours of bypass and the perfusion time in these experiments did not exceed 13 hours. The observation that 24 hours of partial veno-arterial bypass using membrane oxygenators in healthy dogs causes only minor changes in heart and lung function and in lung histology might explain the possibility of using such oxygenators in prolonged perfusions.