title: How useful is determination of anti-factor Xa activity to guide bridging therapy with enoxaparin? A pilot study.
abstract: Low-molecular-weight heparins (LMWH) are commonly used as peri-procedural bridging anticoagulants. The usefulness of measurement of anti-factor Xa activity (anti-Xa) to guide bridging therapy with LMWH is unknown. It was the objective of this study to determine levels of anti-Xa during standard bridging therapy with enoxaparin, and to examine predictors for residual anti-Xa. Consecutive patients receiving enoxaparin at a dosage of 1 mg/kg body weight/12 hours for temporary interruption of phenprocoumon were prospectively enrolled to the study. Blood-samples were obtained 14 hours after LMWH-application immediately pre- procedurally. Procedural details, clinical and demographic data were collected and subsequently analyzed. Seventy patients were included (age 75.2 +/- 10.8 years, Cr Cl 55.7 +/- 21.7ml/min, body mass index [BMI] 27.1 +/- 4.9). LMWH- therapy was for a mean of 4.2 +/- 1.6 days; overall anti-Xa was 0.58 +/- 0.32 U/ml. In 37 (52.8%) of patients anti-Xa was > or U/ml, including 10 (14.3%) patients with anti-Xa > 1U/ml. Linear regression analysis of single variables and logistic multivariable regression analysis failed to prove a correlation between anti-Xa and single or combined factors. No major bleeding, no thromboembolism and four (5.7%) minor haemorrhages were observed. When bridging OAC with therapeutic doses of enoxaparin a high percentage of patients undergo interventions with high residual anti-Xa. The levels of anti-Xa vary largely and are independent of single or combined clinical variables. Since the anti-Xa-related outcome of patients receiving bridging therapy with LMWH is not investigated, no firm recommendation on the usefulness of monitoring of anti-Xa can be given at this stage.
authors.affiliation: Department of Internal Medicine/Cardiology, Robert Koch Strasse 1, 53115 Bonn, Germany. ch.hammerstingl@email.de
authors.forename: Christoph
authors.initials: C
authors.lastname: Hammerstingl
authors.forename: Heyder
authors.initials: H
authors.lastname: Omran
authors.forename: Christian
authors.initials: C
authors.lastname: Tripp
authors.forename: Bernd
authors.initials: B
authors.lastname: Poetzsch
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects; D004334:Drug Administration Schedule; D016903:Drug Monitoring / Q000379:methods*; D017984:Enoxaparin / Q000008:administration & dosage* / Q000009:adverse effects; D065427:Factor Xa Inhibitors; D006470:Hemorrhage / Q000139:chemically induced; D006801:Humans; D019934:International Normalized Ratio; D016014:Linear Models; D016015:Logistic Models; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D010644:Phenprocoumon / Q000008:administration & dosage* / Q000009:adverse effects; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011446:Prospective Studies; D018570:Risk Assessment; D013514:Surgical Procedures, Operative / Q000009:adverse effects*; D013923:Thromboembolism / Q000209:etiology / Q000517:prevention & control*; D016896:Treatment Outcome
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin; D065427:Factor Xa Inhibitors; D010644:Phenprocoumon