Abstract
This study aimed to determine the safety of antithrombotic therapy in children after Fontan surgery and the relationship between bleeding events, blood coagulability, and antithrombotic therapy dosage. We retrospectively evaluated 22 pediatric patients after Fontan surgery at Showa University Hospital and Showa University Northern Yokohama Hospital from March 2011 to September 2020. Patient background, antithrombotic therapy initiation and dosage, and blood coagulability 1 year after surgery were compared between the bleeding and the nonbleeding groups. The median age at the time of Fontan surgery was 36 months （22-164months）. After Fontan surgery, 21 patients underwent warfarin treatment with a median dose of 0.08 mg/kg/day （0.03-0.16mg/kg/day）. Nine patients （41％） experienced bleeding, with median onset at 10 days （1-127） after initiation of antithrombotic therapy. In four cases, antithrombotic therapy was started within 4 days of surgery. Of 11 cases with a prothrombin time and international normalized ratio （PT-INR） ＞ 2 within 4 weeks after initiation of antithrombotic therapy, 4 had bleeding events and 7 cases did not. Among nine patients with bleeding events who were treated with warfarin, six received a dose of ＜0.1mg/kg/day and three received a dose of ＞0.1 mg/kg/day. There was no significant difference between the warfarin dose at antithrombotic therapy initiation and that at the time of bleeding. Additionally, patient without any bleeding event had a PT-INR ＞ 5. The warfarin dose in this case was ＜ 0.1mg/kg/day. There was no relationship between warfarin dose, PT-INR, and bleeding in pediatric patients after Fontan surgery However, PT-INR was unstable during the perioperative period, and some cases exhibited supratherapeutic PT-INR. Therefore, it is crucial to monitor the factors affecting PT-INR （warfarin dosage, combined use of aspirin, postoperative hemodynamics, drug interaction）, particularly for 2 weeks after the initiation of antithrombotic therapy in pediatric patients after Fontan surgery.
