Cardiac surgery in patients with heparin-induced thrombocytopenia using preoperatively determined dosages of iloprost.

Background: Patients with preoperatively diagnosed type II heparin-induced thrombocytopenia (HIT) scheduled for cardiopulmonary bypass (CPB) present a challenge in their intraoperative anticoagulation management because re-exposure to heparin may result in profound thrombocytopenia, intravascular thromboses, bleeding, and even death. Iloprost, a prostacyclin analogue that reversibly inhibits platelet aggregation, has been suggested as a management approach in such cases. The purpose of this study was to assess and confirm the efficacy of a perioperative intravenous iloprost infusion in preventing thromboembolic complications in patients with type II HIT undergoing cardiac surgery and requiring the use of heparin and CPB.
Methods: During a one-and-a-half-year period, 22 patients with type II HIT presented at the Cardiac Surgery Service of the Onassis Cardiac Center in Athens. In these patients, platelet aggregation test results were found strongly positive at heparin serum concentrations corresponding to those achieved during CPB. Iloprost was used in a preoperatively, in vitro-determined, patient-specific concentration that was assessed and modified perioperatively depending on its in vivo effect on platelet aggregation as opposed to the conventional constant rate.
Results: In the 22 patients, the preoperatively determined concentration of iloprost seemed to correlate well with the in vivo interruption of platelet aggregation, as tested by a perioperative heparin-induced platelet aggregation (HIPA) assay, and in only 3 cases (14%) was the rate of iloprost infusion increased. The patients' platelet counts, which were evaluated peri- and postoperatively, were preserved with no statistically significant fluctuations. Postoperative bleeding was within normal limits and no thrombotic episodes or other complications were reported.
Conclusion: Although a number of alternative anticoagulation methods, such as the use of another anticoagulant (danaparoid sodium and recombinant hirudin) or the preoperative use of a defibrinogenating agent (ancorod), have been suggested for patients with type II HIT requiring anticoagulation during CPB, the use of heparin associated with a potent platelet inhibitor such as the prostacyclin analog iloprost is, as this study confirmed, the only to-date safe and effective choice.