Erythrocyte survival following extracorporeal circulation. A question of membrane versus bubble oxygenator

Five groups of seven dogs were studied. Each animal had 250 ml of blood withdrawn and tagged with Cr51. Group I (control) samples were combined with 500 ml of lactated Ringer's solution and reinfused into the respective animals after 3 hours of incubation at 37 degrees C. Group II samples were pumped in a closed-circuit bubble oxygenator with 500 ml of lactated Ringer's prime for 2 hours before reinfusion into the animals. Group III samples were pumped in a bubble oxygenator for 3 hours before reinfusion. Group IV samples were pumped in a closed-circuit membrane oxygenator for 2 hours, and Group V samples were pumped in a membrane circuit for 3 hours. All extracorporeal pump runs were performed at 37 degrees C. Blood samples were drawn from the dogs at regular intervals after bypass for 30 days. Erythrocyte survival was determined by Cr51 activity recorded by a gamma counter. The red cell half-life was determined for each dog. The control half-life was 24.1 +/- 2.03 days; Group II, 19.88 +/- 1.69 (p < 0.05); Group III, 9.63 +/- 1.4 (p < 0.001); Group IV, 19.4 +/- 1.65 (p < 0.05); and Group V, 9.13 +/- 1.45 (p < 0.001). These data indicate that serious red cell injury does occur with extracorporeal circulation but that the injury is a function of pump time, rather than of the type of oxygenator.