['The purpose of this study was to determine whether the use of low-molecular-weight heparin before coronary artery bypass surgery would be associated with an increase in bleeding and use of blood products after the operation.', 'Sixty-four patients (48 men and 16 women) aged 64 +/- 10 years who were undergoing primary coronary artery bypass surgery were prospectively studied. Forty-one patients were treated with either subcutaneous enoxaparin 1 mg/kg twice daily (n = 21; enoxaparin group) or intravenous heparin (n = 20; heparin group). Patients received the last dose of enoxaparin 8.7 +/- 0.75 hours (range, 8-10 hours) before skin incision. Heparin was stopped before transfer to the operating room. An additional 23 consecutive patients who received neither enoxaparin nor heparin served as controls (n = 23). Anti-factor Xa activity, a measure of enoxaparin and heparin activity, was measured at the start of the operation in all patients.', 'There was no perioperative mortality. The length of stay and frequency of postoperative complications were similar between groups. Preoperative anti-factor Xa activity was present only in the enoxaparin group (0.43 +/- 0.25 IU/mL). Chest tube drainage at 24 hours was 553 +/- 160 mL, 532 +/- 140 mL, and 587 +/- 230 mL for the enoxaparin, heparin, and control groups, respectively (P =.48). There was no difference among groups in the amount of blood products transfused.'] Is preoperative use of enoxaparin a risk factor for postoperative bleeding after coronary artery bypass surgery?