In vitro generation of C3a anaphylatoxin by an extracorporeal circuit

The generation of C3a anaphylatoxin was studied during the equilibration of fresh whole blood in an extracorporeal circuit with oxygenator before institution of cardiopulmonary bypass. Twenty-seven units of whole blood were each recirculated through an extracorporeal circuit for periods up to 17 minutes Following an equilibration period of 7 ± 3.5 min, the C3a concentration increased from 563.1 ± 48.4 to 802.1 ± 73.7 ng/ml, corrected for haematocrit (p < 0.01). The increase in C3a was, however, not related to duration of equilibration time. In vivo studies by others reported higher peak levels of C3a and a correlation with duration of cardiopulmonary bypass. Our data confirm that the extracorporeal circuit is an important site of complement activation, but suggest that during cardiopulmonary bypass, other sites or mechanisms may also generate C3a.