Heparin resistance in severe thermal injury: a prospective cohort study

Research output: Contribution to journalArticlepeer-review

Authors

  • Liam Cato
  • Benjamin Bailiff
  • Joshua Price
  • William Lester
  • Christopher Wearn
  • Naiem Moiemen
  • Paul Harrison

Abstract

Background: Low molecular-weight heparin (LMWH) is routinely administered to burn patients for thromboprophylaxis. Some studies have reported heparin resistance, yet the mechanism(s) and prevalence have not been systematically studied. We hypothesised that nucleosomes, composed of histone structures with associated DNA released from injured tissue and activated immune cells in the form of neutrophil extracellular traps (NETs or NETosis), neutralise LMWH resulting in suboptimal anti-coagulation, assessed by reduction in anti-factor Xa activity.

Methods: Blood was sampled from >15% TBSA burn patients receiving LMWH on days 5, 10 and 14. Peak anti-factor Xa (AFXa) activity, anti-thrombin (ATIII) activity, cell-free DNA (cfDNA) levels and nucleosome levels were measured. Mixedeffects regression adjusted for multiple confounders, including injury severity and ATIII activity, and was used to test the association between nucleosomes and AFXa.

Results: 30 patients with severe burns were included. Mean TBSA 43% (SD 17). 23 (77%) patients were affected by heparin resistance (defined by AFXa activity <0.2IU/ml). Mean peak AFXa activity across samples was 0.18 IU/ml (SD 0.11). Mean ATIII was 81.9 %activity (SD 20.4). Samples taken at higher LWMH doses were found to have significantly increased AFXa activity, though the effect was not observed at all doses, at 8000IU no samples were heparin resistant. Nucleosome levels were negatively correlated with AFXa (r = -0.29, p=0.050) consistent with the hypothesis. The final model, with peak AFXa as the response variable, wasadjusted for nucleosome levels (p=0.0453), ATIII activity (p=0.0053), LMWH dose pre-sample (p=0.0049), drug given (enoxaparin or tinzaparin) (p=0.03), and other confounders including severity of injury, age, gender, time point of sample.

Conclusions: Heparin resistance is a prevalent issue in severe burns. Nucleosome levels were increased post-burn, and showed an inverse association with AFXaconsistent with the hypothesis that they may interfere with the anticoagulant effect of heparin in vivo and contribute to heparin resistance. Accurate monitoring of AFXa activity with appropriate therapy escalation plans are recommended with dose adjustment following severe burn injury.

Bibliographic note

Not yet published as of 27/08/2021.

Details

Original languageEnglish
JournalBurns & Trauma
Publication statusAccepted/In press - 30 Jun 2021