ABSTRACT
PURPOSE: This study compared anti-Xa activity in critically ill patients receiving UFH for VTE prophylaxis between two weight groups (<100â¯kg vs ≥100â¯kg). METHODS: This prospective, observational study included critically ill patients on UFH 5000 or 7500â¯units every 8â¯h. A peak and trough anti-Xa activity assay was ordered for each patient at steady state. Goal peak anti-Xa activity was 0.1-0.3â¯units/mL. RESULTS: From March 2017 to June 2018, 75 patients were enrolled with 44 in the <100â¯kg group and 31 in the ≥100â¯kg group. There was no significant difference in the percentage of patients with peak anti-Xa activity within goal range between patients <100â¯kg andâ¯≥â¯100â¯kg (55.3% vs 35.7%, pâ¯=â¯0.12). The odds ratio for achieving peak anti-Xa activity within goal range as weight-based dose increased was 1.03 (95% CI 0.99-1.07). No differences were found in trough anti-Xa activity, VTE, bleeding, length of stay, or death. CONCLUSIONS: Though only one-third of patients ≥100â¯kg had peak anti-Xa activity within goal range, no significant difference was found between the weight groups. Additional prospective studies with adequate sample sizes are warranted to further investigate appropriate weight-based dosing of UFH in critically ill patients.