Key result
In neurocritically ill patients receiving prophylactic subcutaneous heparin, there was poor concordance between aPTT and anti-factor Xa assays.
Why the study?
Although routine laboratory monitoring is not recommended for prophylactic subcutaneous heparin, aPTT prolongation and associated hemorrhage have been reported in neurocritically ill patients, prompting evaluation of assay concordance.
Observational (n=42)
No
Answers are grounded in this paper and cite their sources.
In neurocritically ill patients receiving prophylactic subcutaneous unfractionated heparin, there is poor concordance between aPTT and anti-factor Xa, suggesting aPTT prolongation may not solely reflect heparin activity.
Background: Laboratory monitoring is not recommended when subcutaneous unfractionated heparin (SQ-UFH) is administered at prophylactic doses. However, aPTT prolongation and associated hemorrhage has been reported in the neurocritically ill. At our institution, Neuroscience Intensive Care Unit (Neuro-ICU) patients with prolonged aPTT are further evaluated with a follow up aPTT and anti-factor Xa. Purpose: The purpose of this study was to describe concordance between aPTT and anti-factor Xa in neurocritically ill patients receiving prophylactic SQ-UFH with evidence of aPTT prolongation. Methods: A retrospective chart review of adult patients admitted to the Neuro-ICU from June 2017 to June 2019 was performed. Patients were included if they received SQ-UFH with aPTT levels and at least one anti-factor Xa level drawn within one hour of each other. Concordance between paired aPTT and anti-factor Xa was evaluated using Cohen's weighted kappa. Results: Forty two patients with 56 paired aPTT and anti-factor Xa levels were included. The most prescribed SQ-UFH regimen was 5000 units every 8 hours (60.7%) and anti-factor Xa levels were drawn a median (IQR) of 5.7 (3.1-10.7) hours after the SQ-UFH dose. Only 16 (28.6%) pairs were in concordance. The analysis showed a weighted kappa of .09; 95% CI [-.05 to .22] indicating poor agreement. Conclusions: In neurocritically ill patients receiving prophylactic SQ-UFH with aPTT prolongation, there was poor concordance between aPTT and anti-factor Xa. This suggests that aPTT prolongation may not be solely driven by heparin activity and further evaluation of mechanistic drivers for coagulopathy in this population is necessary.
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Shinn et al. (2023) conducted an observational in Neurocritically ill with aPTT prolongation (n=42). Subcutaneous unfractionated heparin (SQ-UFH) was evaluated on Concordance between paired aPTT and anti-factor Xa (weighted kappa 0.09, 95% CI -0.05 to 0.22). In neurocritically ill patients receiving prophylactic subcutaneous heparin, there was poor concordance between aPTT and anti-factor Xa assays.
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