Heparin-bonded surfaces in extracorporeal membrane oxygenation for cardiac support

Development of increasingly complex perfusion devices with bonded heparin allowed for significant improvement of thromboresistance of most basic components required for cardiopulmonary bypass. In his recent review of heparin-coated cardiopulmonary bypass circuits, Gravlee cited 91 references dealing with heparin-coated surfaces, and far more can be found if the search includes material technology or heparin-coated devices not designed for cardiopulmonary bypass (eg, ventricular assist devices, hemofilters, catheters). The present review is focused on long-term application of heparin-coated equipment in conjunction with basic work on heparin bonding relevant for extracorporeal membrane oxygenation. Experimental open chest cardiopulmonary bypass using heparin-coated equipment without systemic heparinization up to 36 hours has shown improved thromboresistance, and better platelet preservation was demonstrated for perfusion with heparin-coated cardiopulmonary bypass equipment up to 5 days in the experimental set-up. Similar findings were reported for roller pump perfusion with heparin-coated tubing and centrifugal pump perfusion with heparin-coated pump heads. More recently, heparin bonding was also made available for oxygenators with true membranes that preclude plasma leakage. The available knowledge on clinical applications of heparin-coated perfusion equipment is mainly based on short-term applications like ours, which now includes more than 300 patients. Reduced postoperative blood loss and as a result fewer transfusions were the main benefits of heparin-coated equipment allowing for perfusion with low systemic heparinization. There are only a few reports on long-term use of heparin-coated equipment for prolonged circulatory support. However, the longest clinical application of a single device is that of an intravascular gas exchanger that remained fully functional during a 29-day implantation period. Finally, it appears, that circulating protamine interacts with surface-bound heparin. Protamine administration should therefore be avoided during perfusion with heparin-bonded equipment to maintain the improved thromboresistance.