Scanning electron microscopic comparison between the thrombogenic properties of heparinized and non-heparinized vena cava catheters. A long-term study.

In an experimental comparative study on rabbits, the efficacy of the reduction of surface thrombus formation was investigated using heparinized central venous catheters compared with non-heparinized. Up to a central indwelling period of ten days, there was a reduction of the thrombus layer thickness on the heparinized catheters of 80% (with a trial duration of three days this was as much as 90%). The action of the stabilized surface heparin, which leads to a substantial thromboresistance, is complex in nature. 1) By intensified adsorption of plasma proteins in the early phase (proteins consist of antithrombin III, factor IX, X and XI), there is very much less thrombocyte adhesion and aggregation on the heparinized catheter surfaces. 2) The externally orientated negative net charge of the heparin shows a similar effect. 3) If there is thrombocyte adhesion despite this, further heparin effects become more prominent. Thus the release of ThF 3 and ADP, which leads to aggregation, is markedly inhibited. On the other hand, this leads to easier dissolution of already aggregated thrombocytes and on the other to a reduction of the catalytic thrombocyte surface for the plasma clotting factors. 4) This effect is supported by the increased adsorption of antithrombin III onto the control surface. 5) Finally there is also an inhibitory effect of heparin on the activated Stuart-Prower factor. Local thrombosis on the venous catheter surface can thus be effectively reduced by local therapy, without greater risks for the intensive care patient.