BJA Advance Access originally published online on July 27, 2006
British Journal of Anaesthesia 2006 97(4):453-459; doi:10.1093/bja/ael194
Anticoagulation monitoring during vascular surgery: accuracy of the Hemochron® low range activated clotting time (ACT-LR)
1 Department of Anaesthesiology, Hôpital Foch Suresnes, France
2 Department of Biology, Hôpital Foch Suresnes, France
*Corresponding author. E-mail: m.fischler{at}hopital-foch.org
Background. Activated clotting time (ACT) is currently used to monitor high concentrations of heparin anticoagulation. A new instrument, the Hemochron® Jr Signature device, has been specifically designed to measure ACT in low-range heparin plasma concentrations (ACT-LR). The purpose of this study was to compare ACT-LR with anti-Xa activity in patients receiving low-dose i.v. heparin during vascular surgery.
Methods. Thirty patients, undergoing arterial vascular surgery, were included in the study and received unfractionated heparin (initial dose 50 u kg1). One hundred and thirty-two pairs of blood samples were simultaneously collected during surgery to determine ACT-LR and anti-Xa activity. Pearson correlation, Kappa test, ROC curve and a specific clinical interpretation of the correlation were performed.
Results. ACT-LR ranged from 68 to 380 s, anti-Xa activity from 0 to 1.45 u ml1. We observed a strong correlation between anti-Xa activity and ACT-LR (r2=0.87; P<0.0001). Accuracy of ACT-LR was good for anti-Xa activity up to 0.6 u ml1 (Kappa, 0.94; accuracy, 97%) and 0.8 u ml1 (Kappa, 0.79; accuracy, 90%), and poor for anti-Xa activity above 1 u ml1 (Kappa, 0.59). A clinical interpretation of the correlation graph found 98% of measured ACT-LR values to be accurate.
Conclusion. Hemochron® Jr Signature provides measurements of ACT-LR, which are accurate for monitoring heparin anticoagulation at anti-Xa activity below 0.8 u ml1.
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