JACC: Bedside test reliably measures enoxaparin clotting time

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Researchers have found that the bedside test, Hemonox CT [clotting time], can be used as a reliable method to monitor enoxaparin (Lovenox, Sanofi-Aventis) anticoagulation therapy before catherization and PCI and can provide better anticoagulation therapy compared to unfractionated heparin (UFH) if well managed, according to a study published Feb. 16 in the Journal of the American College of Cardiology.

“Current guidelines from the European Society of Cardiology and other international societies strongly recommend enoxaparin in the treatment of STEMI in association with fibrinolysis, in the treatment of non-STEMI acute coronary syndrome (ACS) for invasive strategy and for conservative strategy,” according to the authors.

Johanne Silvain, MD, of the Université Paris, and colleagues evaluated the Hemonox CT (International Technidyne) test on 296 patients to help identify those with anti-Xa activity levels out of therapeutic range.

“Chromogenic anti-Xa activity level is the standard laboratory assay for monitoring the anticoagulant effect of low molecular weight heparin (LMWH) [such as enoxaparin] but is not available at the bedside, and activated clotting time is not discriminant enough for enoxaparin anticoagulation therapy,” the authors wrote.

Of the 296 patients, 71.6 percent received IV enoxaparin in a dose of 0.5 mg/kg, 21.6 percent received subcutaneous (SQ) enoxaparin at a dose of 1 mg/kg/12 h and 7.1 percent received 0.25 mg/kg IV bolus in addition to SQ enoxaparin if the last SQ dose was administered eight to 12 hours before catheterization.

Researchers found that “enoxaparin-treated patients with inadequate anti-Xa activity (greater than 0.5 IU/ml) can be accurately and easily identified by the Hemonox bedside test, with a high sensitivity (94.9 percent) when using a 120 second threshold.”

In addition, the results showed that the enoxaparin dose was associated with anti-Xa activity in a therapeutic range between 0.5 and 1.8 IU/ml in 95 percent of patients with low rates of under- or over-anticagulated patients, 4 percent and 1 percent, respectively.

The researchers found that patients who were due to undergo PCI who had an anti-Xa activity greater than 0.5 IU/ml were at greater risk of ischemic complications.

“Because the main objective of the monitoring test is its level of sensitivity for defining patients who are under-anticoagulated, the threshold of 120 seconds may be recommended, especially in patients at high risk of thrombosis,” the authors wrote.

The results showed that for patients without prior anticoagulation, an IV enoxaparin bolus of 0.5 mg/kg yields an average anti-Xa activity of 0.73 IU/ml. The authors concluded that for these patients, they would not be over-anticoagulated even with an additional IV bolus.

“The Hemonox test may be used in the catheterization laboratory to assess the appropriate level of anticoagulation therapy in patients undergoing PCI and to avoid the use of unfractionated heparin in addition to enoxaparin,” the authors concluded. “Compared with unfractionated heparin, enoxaparin provides more predictive and more stable anticoagulation therapy.”