It is important to determine the optimal conditions of extracorporeal membrane oxygenation (ECMO) for the treatment of diseased lung with severe acute respiratory failure. The purpose of this study is to evaluate the effects of hypothermic perfusion by ECMO. Veno-venous ECMO was performed in 13 mongrel dogs. The blood drainage catheter was inserted into the right atrium through the right external jugular vein and the blood return catheter was inserted into the left femoral vein. The temperatures of the priming solution and the heat exchanger were adjusted to 33 degrees C for Group A (n = 6) and 37 degrees C for Group B (n = 7). Before starting ECMO and at 10, 30, 60, 120, 180, and 300 minutes after starting ECMO, the pulmonary arterial blood temperature and the esophageal temperature were measured and the blood samples were obtained from the abdominal aorta. The leukocyte count, platelet count, leukotriene B4 (LTB4) level, vitamin E level and total hemolytic complement (CH50) level were determined. The pulmonary arterial blood and esophageal temperatures approached about 33 degrees C in Group A and about 37 degrees C in Group B at 60 minutes of ECMO and remained stable until the end of ECMO. The leukocyte count did not change significantly in Group A, but was significantly elevated in Group B at 60, 120, 180, and 300 minutes of ECMO when compared with before ECMO. The leukocyte count in Group A was significantly lower than that in Group B at 120, 180, and 300 minutes of ECMO. There were no significant differences between the platelet counts of the two groups. The LTB4 level was always lower than before ECMO in Group A, and was always higher than before ECMO in Group B.(ABSTRACT TRUNCATED AT 250 WORDS)