Warfarin anticoagulation after congenital heart surgery at a large children's hospital

Management of warfarin in pediatric patients remains a clinical challenge. Warfarin may be administered after congenital heart surgery, and the risks of morbidity can be high. Currently, no data exist to describe the initiation of warfarin and the risk factors for morbidity in post-congenital heart surgery patients. This study aimed to characterize the time required to reach anticoagulation for patients administered warfarin therapy after cardiac surgery and to identify and characterize the risk factors for supratherapeutic anticoagulation and adverse events after warfarin initiation. This retrospective study reviewed all patients between 2006 and 2011 who received warfarin anticoagulation after cardiac surgery at our institution. Factors associated with a prolonged time required to reach an international normalized ratio (INR) of 2 and factors related to supratherapeutic anticoagulation (INR ≥ 4) were identified. The inclusion criteria were met by 59 patients. The median time required to reach an INR of at least 2 after initiation of warfarin was 2 days (interquartile range (IQR), 2-4). The only groups that required a significantly longer time to reach an INR of 2 were those with a postoperative delay in initiation of warfarin and those receiving heparin anticoagulation before and during warfarin initiation. Nine patients experienced an INR of 4 or more. However, no thrombotic events occurred, and significant bleeding was uncommon. In the largest reported group of patients undergoing anticoagulation after cardiac surgery, warfarin was well tolerated across all age groups. The median time required to reach an INR of 2 after loading with warfarin was 2 days, and adverse events were uncommon.