Comparison of Time Within Therapeutic Range Using Anti-Factor Xa Versus Activated Partial Thromboplastin Time Monitoring of Unfractionated Heparin in Children

Abstract

OBJECTIVE To compare unfractionated heparin (UFH) monitoring using time in therapeutic range of activated partial thromboplastin time (aPTT) versus anti-factor Xa activity (anti-Xa) in children. METHODS This retrospective chart review, with data between October 2015 and October 2019, included pediatric patients younger than 18 years on therapeutic UFH infusion with aPTT or anti-Xa monitoring. Patients receiving extracorporeal membrane oxygenation, dialysis, concomitant anticoagulants, prophylactic UFH, no stated goal, and UFH administered for less than 12 hours were excluded. The primary outcome compared the percentage of time in therapeutic range between aPTT and anti-Xa. Secondary outcomes included time to first therapeutic value, UFH infusion rates, mean rate adjustments, and adverse events. RESULTS A total of 65 patients were included, with 33 aPTT patients and 32 anti-Xa patients, representing 39 UFH orders in each group. Baseline characteristics were similar between groups, with an overall mean age of 1.4 years and mean weight of 6.7 kg. The anti-Xa cohort demonstrated a statistically significantly higher percentage of time in therapeutic range compared with the aPTT group (50.3% vs 26.9%, p = 0.002). The anti-Xa group also demonstrated a trend toward decreased time to first therapeutic value compared with aPTT (14 vs 23.2 hours, p = 0.12). Two patients in each group experienced new or worsening thrombosis. Six patients in the aPTT cohort experienced bleeding. CONCLUSIONS This study demonstrated greater time was spent within therapeutic range for children receiving UFH monitored with anti-Xa compared with aPTT. Future studies should assess clinical outcomes in a larger population.