Use of Anti-Xa Activity as a Marker for Heparin-Induced Bleeding in Patients with APTT >180 s

Abstract

Heparin is administered as an anticoagulant in treatment of or prophylaxis against arterial or venous thromboembolism, in treatment of myocardial infarction, and during cardiac surgery (cardiopulmonary bypass) (1), coronary angioplasty, and other procedures (2). Heparin treatment demands laboratory control and is monitored by determining the activated partial thromboplastin time (APTT), which should be adjusted to stay within 1.5–2 times the control value (3). Sometimes during therapy high APTT values (>180 s) are reached (4), and physicians decide to interrupt the treatment for a few hours because of the great risk of hemorrhagic complications, the most important side effect of heparin therapy (5). In these situations, however, the true concentrations of heparin in the patient’s plasma are really unknown. Moreover, in some described cases, the APTT values were prolonged because of underlying disease (severe liver disorders, extensive myocardial infarction, or infection) and postoperative complications after cardiac surgery (6). This prolongation of APTT was not heparin related, although the results of the APTT test falsely suggested a higher heparin concentration (7). Another problem is that sensitivity of the reagents for the APTT test varies greatly, and the physicians who prescribe heparin on the basis of certain APTT ratios may order different doses of heparin and produce different amounts of anticoagulation in their patients (3). In cases with …