PB0278 - To Load or not to Load: Safety and Efficacy of Warfarin Dosing in Pediatric Cardiology Patients

Background: Warfarin (Coumadin®) is a vitamin K antagonist that may take 72-96 hours to exhibit peak anticoagulation effects. Some current guidelines recommend initiating pediatric patients with a loading dose (LD) of 0.2 mg/kg per dose. Due to the paucity of data in regard to administering a LD, this study evaluated the utility of utilizing a LD in pediatric cardiology patients requiring warfarin initiation.

Aims: 1. Compare the rates of therapeutic, supratherapeutic, and subtherapeutic INR within the first 7 days after warfarin initiation with a LD compared to no loading dose (NLD)
2. Evaluate the safety and efficacy of warfarin initiation with a LD versus NLD

Methods: A retrospective chart review evaluated patients 0 to 18 years of age admitted to the heart center for warfarin initiation between 01/01/2018 and 12/31/2020. The two groups compared are an initial LD of warfarin (> 0.15 mg/kg/dose) versus NLD ( < 0.15 mg/kg/dose).

Results: Twenty-one patients were included for final analysis with 14 in the LD group and 7 in the NLD group. Baseline characteristics were similar amongst both groups except patients in the NLD group were significantly older (66 months +¬ 8 vs 139 months + 72) and weighed significantly more (15.8 kg +¬ 8 vs 44.1 kg + 18). There was no difference in the rate of therapeutic (5, 36% vs 1, 14%), subtherapeutic (1, 7% vs 0, 0%), or supratherapeutic (8, 57% vs 6, 86%) INR between the LD and NLD group respectively. There were no difference in minor bleeding rates (0, 0% vs 1, 14%) and no major bleeding events occurred.

Conclusion(s): There was no difference in target INR achievement in patients in the LD and NLD groups. There was a high overall rate of supratherapeutic INR values in both groups; however, very low rates of bleeding. Pediatric cardiology patients may not require warfarin loading doses.