[A case of heparin-induced thrombocytopenia associated with unexpected excessive argatroban anticoagulation after abdominal aortic aneurysm resection].

We experienced excessive anticoagulation induced by argatroban for the treatment of heparin-induced thrombocytopenia (HIT). A 74-year-old man was scheduled for elective abdominal aortic aneurysm resection. During the surgery, both femoral arteries were found non-pulsatile requiring thrombectomy. The next day, second laparotomy was needed because of superior mesenteric artery occlusion. After the surgery, acute renal failure and hypoxemia continued with progressive thrombocytopenia necessitating frequent administration of platelet concentrates. Considering possibility of HIT, we stopped heparin and began argatroban. Due to his mild liver dysfunction, we initiated argatroban at 0.5 microg x kg(-1) x min(-1) one-fourth of standard initial dose, according to its drug information approved by FDA. Although expected APTT level was from 50 to 60 sec, it increased immediately up to 93 sec. Excessive anticoagulation continued more than 24 hours after cessation of argatroban and bleeding occurred from the tracheostomy site. When APTT decreased to the target range, we restarted argatroban and found the adequate dosage at 0.08 microg x kg(-1) x min(-1). After argatroban treatment, platelet count recovered immediately and no thromboembolism was observed. We recommend that argatroban should be initiated at a lower dosage than the dose shown in its drug information for HIT patients after cardiovascular surgery with frequent monitoring of APTT.