The treatment of heparin resistance with Antithrombin III in cardiac surgery

Purpose: To report three patients who developed heparin resistance during c ardiac surgery which was successfully managed with 1000 U Antithrombin III (AT III). Clinical features: We observed heparin resistance prior to cardiopulmonary bypass (CPB) in one patient and during the CPB in two patients. In the firs t patient who was scheduled for mitral valve replacement, although heparin was administered sequentially up to 500 U . kg(-1) prior the CPB, the ACT v alue was 354 sec. After 1,000 U ATIII were administered the ACT was 395 sec and CPB was initiated. The ACT remained between 496 and 599 sec throughout CPB and a total of 260 mg protamine sulfate was given. In the other two pa tients following 300 U . kg(-1) heparin, the ACT was up to 400 sec and CPB was initiated During CPB, ACT were decreased 360 sec and 295 sec in patient s II and III respectively. Although heparin was added 1,500 U, ACT increase d to greater than or equal to 400 sec could not be achieved. In the second patient ATIII activity was found 10%. After the administration of 1,000 U A TIII, ATIII activity was found to be 67% 40 min later and ACT were increase d up to 400 sec. There was no thrombosis within the extracorporeal circuit, additional heparin was not required, less protamine was administered (less than or equal to 3 mg . kg(-1)) and ro excessive postoperative bleeding wa s observed in all patients. Conclusion: We recommend that AT III supplementation should be considered t o manage heparin resistance prior or during CPB in patients undergoing open heart surgery.