Prolonged perfusion with a membrane oxygenator in awake ponies.

Prolonged extracorporeal membrane oxygenation (PEMO) was performed in 6 adult ponies with the membrane oxygenator in vein-to-artery bypass circuit. A flow rate equal to 46 per cent of control cardiac output was diverted through the PEMO circuit of 10 to 24 hours. Three of the 6 ponies were perfused for at least 20 hours and developed no complications. Immediately following initiation of PEMO, left ventricular output decreased; however, in the interval between 6 and 24 hours, left ventricular output was increased above control levels. Aortic pressure and left ventricular work were markedly elevated during PEMO. Pulmonary ventilation and oxygen uptake also decreased initially but were elevated during later stages of bypass. Pulmonary compliance did not change, except in those studies in which problems were encountered with perfusion techniques. Hepatic glycolysis and hyperglycemia occurred and were more severe in ponies with catheter-produced thrombi. Marked diuresis, which could be attributed only partially to the hyperglycemia, was present throughout PEMO. Based on the minimal morphologic changes observed in the ponies, extracorporeal circulation diverting one half of the cardiac output through a membrane oxygenator can be safely performed for up to 24 hours.