Prevention of Venous Thromboembolism in Microvascular Surgery Patients Using Weight-Based Unfractionated Heparin Infusions

J Reconstr Microsurg. 2022 Jun;38(5):395-401. doi: 10.1055/s-0041-1735225. Epub 2021 Aug 24.

Abstract

Background: Unfractionated heparin infusions are commonly used in microvascular surgery to prevent microvascular thrombosis. Previously, fixed-dose heparin infusions were believed to provide sufficient venous thromboembolism (VTE) prophylaxis; however, we now know that this practice is inadequate for the majority of patients. Anti-factor Xa (aFXa) level is a measure of unfractionated heparin efficacy and safety. This study evaluated the pharmacodynamics of weight-based dose heparin infusions and the impacts of real-time aFXa-guided heparin dose adjustments.

Methods: This prospective clinical trial enrolled adult microvascular surgery patients who received a weight-based heparin dose following a microsurgical procedure. Steady-state aFXa levels were monitored, and patients with out-of-range levels received dose adjustments. The study outcomes assessed were aFXa levels at a dose of heparin 10 units/kg/hour, time to adequate aFXa level, number of dose adjustments required to reach in-range aFXa levels, and clinically relevant bleeding and VTE at 90 days.

Results: Twenty-one patients were prospectively recruited, and usable data were available for twenty patients. Four of twenty patients (20%) had adequate prophylaxis at a heparin dose of 10 units/kg/hour. Among patients who received dose adjustments and achieved in-range aFXa levels, the median number of dose adjustments was 2 and the median weight-based dose was 11 units/kg/hour. The percentage of patients with in-range levels was significantly increased (65 vs. 15%, p = 0.0002) as a result of real-time dose adjustments. The rate of VTE at 90 days was 0%, and clinically relevant bleeding rate at 90 days was 15%.

Conclusion: Weight-based heparin infusions at a rate of 10 units/kg/hour provide a detectable level of anticoagulation for some patients following microsurgical procedures, but most patients require dose adjustment to ensure adequate VTE prophylaxis.

Publication types

  • Clinical Trial

MeSH terms

  • Adult
  • Anticoagulants / therapeutic use
  • Heparin
  • Humans
  • Microsurgery
  • Prospective Studies
  • Venous Thromboembolism* / drug therapy
  • Venous Thromboembolism* / prevention & control

Substances

  • Anticoagulants
  • Heparin