CARDIAC OXYGENATION BY EXTRACORPOREAL MEMBRANE-OXYGENATION IN EXTERIORIZED FETAL LAMBS

OBJECTIVE: The purpose of this study was to determine the degree of ca rdiac oxygenation produced by different routes of extracorporeal membr ane oxygenation in fetal lambs submerged in warm saline solution. STUD Y DESIGN: Seven fetal lambs ranging in age from 113 to 133 days of ges tation were delivered by cesarean section and oxygenated with extracor poreal membrane oxygenation. To maintain the patency of the ductus art eriosus, prostaglandin E(1) was continuously infused intravenously to the fetus. Initially the extracorporeal membrane oxygenation route was from the right atrium to the carotid artery. Then the extracorporeal membrane oxygenation route was changed to flow from the right atrium t o the umbilical vein. The fetus was kept in a warm saline solution bat h, and the fetal circulation was maintained, Extracorporeal membrane o xygenation flow ranged between 100 and 200 ml/min throughout the exper iment. Simultaneous blood samples were taken during both types of extr acorporeal membrane oxygenation from the following points in the fetal circulation: premembrane (least oxygenated blood leaving the fetus fr om the right atrium), postmembrane (oxygenated blood returning to the fetus), the carotid artery, and the left ventricle. The respiratory ga ses and pH of each sample were measured. Six fetuses received nonradio active colored microspheres injected into the oxygenated blood returni ng to the fetus flow before returning to the fetuses during both types of extracorporeal membrane oxygenation. After the animals were killed , microspheres were counted in the myocardium separately taken from th e right and left atria and the right and left ventricles to determine cardiac blood flow. RESULTS: During right atrium to carotid artery ext racorporeal membrane oxygenation, left ventricle Po-2 remained low as postmembrane Po-2 increased; these values were not significantly corre lated (r = 0.234, p = 0.61). During right atrium to umbilical vein ext racorporeal membrane oxygenation, left ventricle and postmembrane Po-2 exhibited a significant positive correlation (r = 0.855, p = 0.014). When the extracorporeal membrane oxygenation route was switched from t he right atrium to carotid artery to the right atrium to umbilical vei n, there was a significant increase in left ventricle Po-2 and a decre ase in left ventricle Pco(2), whereas the respiratory gases and pH rem ained unchanged at other sites in the circulation. Microsphere counts were consistently higher during right atrium to umbilical vein extraco rporeal membrane oxygenation than during right atrium to carotid arter y extracorporeal membrane oxygenation in all four samples from differe nt parts of myocardium (p < 0.001 by paired t test). CONCLUSION: More effective cardiac oxygenation is provided by right atrium to umbilical vein extracorporeal membrane oxygenation than by right atrium to caro tid artery extracorporeal membrane oxygenation.