Anti-Xa activity by weight in critically ill patients receiving unfractionated heparin for venous thromboembolism prophylaxis

Meera V. Aggarwal, Andrew S. Jarrell, Vi T. Gilmore, Jonathan K. Aboagye, Elliott R. Haut, Deborah B. Hobson, Brandyn D. Lau, Thomas Kickler, Peggy S. Kraus, Dauryne L. Shaffer, Kenneth M. Shermock, Michael B. Streiff, Gang Zheng, Rachel M. Kruer

Research output: Contribution to journalArticle


Purpose: This study compared anti-Xa activity in critically ill patients receiving UFH for VTE prophylaxis between two weight groups (<100 kg vs ≥100 kg). Methods: This prospective, observational study included critically ill patients on UFH 5000 or 7500 units every 8 h. A peak and trough anti-Xa activity assay was ordered for each patient at steady state. Goal peak anti-Xa activity was 0.1–0.3 units/mL. Results: From March 2017 to June 2018, 75 patients were enrolled with 44 in the <100 kg group and 31 in the ≥100 kg group. There was no significant difference in the percentage of patients with peak anti-Xa activity within goal range between patients <100 kg and ≥ 100 kg (55.3% vs 35.7%, p = 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 ≥100 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.

Original languageEnglish (US)
Pages (from-to)180-185
Number of pages6
JournalJournal of Critical Care
StatePublished - Aug 2019



  • Anti-Xa
  • Deep venous thrombosis
  • Heparin
  • Obese
  • Prophylaxis
  • Venous thromboembolism

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine

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