Deleterious effects of cardiopulmonary bypass. A prospective study of bubble versus membrane oxygenation

A number of hematologic and immunologic parameters that reflect erythrocyte and platelet damage and host defense mechanisms against infection were studied in 20 patients undergoing cardiopulmonary bypass during coronary operations. The patients were randomly assigned to a group in which a bubble oxygenator or a hollow-fiber membrane oxygenator was used. Hemolysis, thrombocytopenia, and significant release of beta thromboglobulin occurred in patients from the bubble oxygenator group and, to much lesser extent, in patients from the membrane oxygenator group. Polymorphonuclear leukocytes and monocytes from bubble oxygenator patients demonstrated increased generation of reactive oxygen species in the resting state and in the presence of the stimulating agents N-formyl-methionyl-leucyl-phenylalanine, concanavalin A, and opsonized zymosan, as compared with cells from membrane oxygenator patients. No difference was found between bubble and membrane oxygenator patients in the time of occurrence or intensity of leukopenia during bypass, of leukocytosis at the end of bypass, nor in the rate of complement activation, as assessed by quantitation of plasma C3a antigen. Complement activation was dependent on the alternative pathway. Immunoglobulin M concentration significantly decreased during bypass in both groups of patients. The serum opsonizing capacity for endotoxin and serum bactericidal activity for Serratia marcescens were decreased in both groups, mainly because of hemodilution, although they were additionally affected by bubble oxygenation. Several deleterious hematologic consequences of cardiopulmonary bypass can be minimized by the use of a membrane oxygenator. However, complement activation remains a potential risk factor even in membrane oxygenator patients and requires further investigation to obtain better hemocompatible materials for cardiopulmonary bypass circuits.