Comparison of three oxygenator-coated and one total-circuit-coated extracorporeal devices

The present study was designed to compare the biocompatibility of three car diopulmonary bypass setups with different surface coatings, and to determin e if coating of the whole circuit with one of the coatings was more benefic ial than coating of the oxygenator only. Extracorporeal devices entirely coated with synthetic polymers (Avecor, n = 6) were compared to oxygenators coated with synthetic polymers (Avecor, n = 6), end-point, covalently attached heparin (CBAS, n = 6) or absorbed hepa rin (Duraflo 2, n = 6) in an in vitro model of a heart-lung machine. The ci rcuits were primed with fresh human whole blood and Ringer's acetate and re circulated at 4 l/min at 30 degrees C for 2 h. Test samples were obtained a t regular intervals and analysed for myeloperoxidase (MPO). platelet counts , beta-thromboglobulin, heparin. prothrombin fragment 1 + 2, plasmin-anti-p lasmin complexes, and complement activation products. The mean MPO concentrations increased in the Avecor-coated oxygenator group (AV) from 247 at the start to 671 mu g/l at the termination of the experim ents, in the Avecor-coated total circuit group (AV-T) from 116 to 288 mu g/ l, in the Duraflo 2 coated oxygenator group (DU) from 160 to 332 mu g/l, an d in the CBAS-coated oxygenator (CA) group from 172 to 311 mu g/l. The MPO concentrations increased significantly in all groups (p < 0.03). The increa se in group A was significantly higher than in the other three groups (p = 0.007). The mean platelet counts decreased in the Avecor-coated total circu it group from 117 at start to 99 x 10(9)/l at termination of the experiment s, in the Avecor-coated oxygenator group from 119 to 103 x 10(9)/l, in the Duraflo 2 group from 96 to 88 x 10(9)/l, and in the CBAS group from 132 to 123 x 10(9)/l. The platelet counts decreased significantly in all groups (p < 0.01), but the intergroup differences were not significant (p = 0.15). T he mean beta-thromboglobulin concentrations increased in the Avecor-coated total circuit group from 193 at the start to 754 ng/ml at the termination o f the experiments, in the Avecor-coated oxygenator group from 474 to 1654 n g/l. in the Duraflo 2 group from 496 to 1280 ng/l, and in the CBAS group fr om 418 to 747 ng/l. The beta-thromboglobulin increase was significant in ea ch group (p < 0.01). but not between the groups (p = 0.49). The mean heparin concentrations in the Duraflo 2 group increased from 2460 at the start to 2897 IU/l at termination of the experiments, in the CBAS gr oup from 2468 to 2518 IU/l. In the Avecor-coated oxygenator group heparin c oncentrations decreased from 2010 to 1968 IU/l. and in the Avecor-coated to tal circuit group from 2002 to 1927 IU/l. The differences in heparin concen trations were significant between the Duraflo 2 group and the other groups (p < 0.05). The mean prothrombin fragment 1 + 2 concentrations increased in the CBAS group from 0.4 at the start to 2.1 nmol/l at the end of the exper iments, in the Avecor-coated oxygenator group from 0.4 to 0.6 nmol/l, in th e Avecor-coated total circuit group from 0.3 to 0.4 nmol/l, and in the Dura flo 2 group from 1.2 to 1.3 nmol/l. The prothrombin fragment 1 + 2 increase was significant in ail groups to (p < 0.05), but there were no significant intergroup differences (p = 0.54). There were no significant differences a t the termination of the experiments among the four groups regarding comple ment activation as measured by C3 activation products and the terminal comp lement complex. In the present in vitro model of a heart-lung machine, none of the three sp ecific setups with different coatings was superior with regard to all test parameters. The CBAS group generated the highest levels of prothrombin frag ment 1 + 2 formation, but least complement activation. The increasing plasm a heparin concentrations in the Duraflo 2 group indicated more unstable hep arin bonding. The Avecor-coated total circuit group were superior to the Av ecor-coated oxygenator group regarding plasma concentrations of MPO, but no t compared to the CBAS and Duraflo 2-coated oxygenator groups.