Heparin in Patients with HIT II Requiring Complex Cardiac Procedures

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Abstract
The anticoagulative management of patients suffering from heparin-induced thrombocytopenia type II (HIT II) and undergoing cardiac surgery with extracorporeal circulation is still a topic of debate. On the one hand, heparin has been considered contraindicated in these patients until now, and on the other hand, serious complications have occurred with alternative drugs such as r-hirudin, danaparoid-sodium or enoxaparin [ 1 ] [ 2 ] Therefore, we reported on a new strategy for using heparin in these patients [ 3 ]. When no anti-Hep-PF4-antibodies are detectable, heparin can be used for a short period of time, such as anticoagulation for cardiopulmonary bypass, as thromboembolic events only occur when heparin is used in a patient with circulating anti-Hep-PF4-antibodies. Despite accelerated antibody production after heparin reexposure, thromboembolic events do not occur if all complexes of heparin and platelet factor 4 due to the rapid pharmacokinetics of heparin are eliminated before antibody boostering. The advantage of this management is that at least high intraoperative doses of alternative drugs that have a difficult dosing regimen, cannot be antagonized, and show a delayed elimination compared to heparin are avoided, and may reduce the frequency of postoperative bleeding complications. In our experience, even complex cardiac procedures such as implantation of left ventricular assist devices (LVAD) and/or cardiac transplantation, which usually require a prolonged cardiopulmonary bypass time, can be performed safely with this strategy. Furthermore, use of heparin for intraoperative anticoagulation is even possible when more than one cardiac procedure (this means cardiac transplantation after LVAD bridging) has to be performed within a short period of time [ 4 ]. This concept was also reported by others [ 5 ], and it is now our treatment of choice to use heparin for intraoperative anticoagulation and continue postoperative anticoagulation with alternative drugs in HIT II patients tested negative for anti-Hep-PF4-antibodies. This strategy is especially helpful in patients that have to undergo complex cardiosurgical procedures with enhanced risk for postoperative bleeding complications. We would therefore like to encourage other cardiac surgeons to employ this concept.

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