Anticoagulation monitoring during vascular surgery: accuracy of the Hemochron low range activated clotting time (ACT-LR).
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 kg(-1)). 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 ml(-1). We observed a strong correlation between anti-Xa activity and ACT-LR (r(2)=0.87; P<0.0001). Accuracy of ACT-LR was good for anti-Xa activity up to 0.6 u ml(-1) (Kappa, 0.94; accuracy, 97%) and 0.8 u ml(-1) (Kappa, 0.79; accuracy, 90%), and poor for anti-Xa activity above 1 u ml(-1) (Kappa, 0.59). A clinical interpretation of the correlation graph found 98% of measured ACT-LR values to be accurate.


CONCLUSIONS
Hemochron Jr Signature provides measurements of ACT-LR, which are accurate for monitoring heparin anticoagulation at anti-Xa activity below 0.8 u ml(-1).
Tremey
B
B
Department of Anaesthesiology, Hôpital Foch, Suresnes, France.
Szekely
B
B
Schlumberger
S
S
François
D
D
Liu
N
N
Sievert
K
K
Fischler
M
M
D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage*; D001780:Blood Coagulation Tests / Q000295:instrumentation / Q000379:methods; D004334:Drug Administration Schedule; D016903:Drug Monitoring / Q000379:methods*; D065427:Factor Xa Inhibitors; D005260:Female; D006493:Heparin / Q000008:administration & dosage*; D006801:Humans; D007430:Intraoperative Care / Q000379:methods; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D015203:Reproducibility of Results; D014656:Vascular Surgical Procedures
D000925:Anticoagulants; D065427:Factor Xa Inhibitors; D006493:Heparin