A review of systemic anticoagulant use in 517 free flap procedures was performed to determine the associated risk of hematoma formation. Patients were divided retrospectively (not randomly) into five groups: no anticoagulation (227 flaps, 5.3 percent hematomas), low-dose heparin bolus of 2000 to 3000 units and postoperative infusion at a rate of 100 to 400 units/hr for 5 to 7 days (192 flaps, 6.7 percent hematomas), intraoperative bolus of 5000 units of heparin without postoperative anticoagulation (46 flaps, 6.5 percent hematomas), high-dose heparin infusion at a rate of 500 to 1200 units/hr (30 flaps, 20 percent hematomas), and dextran 40 infusion at a rate of 25 ml/hr (22 flaps, 9.1 percent hematomas). Intraoperative blood loss was similar for all groups. The flap loss rate was lower in the bolus (1.0 percent) and low-dose (1.0 percent) heparin groups than in the no-anticoagulation group (4.4 percent), but this difference was not statistically significant. The pedicle thrombosis rate also was lower in the bolus (2.2 percent) and low-dose (2.1 percent) heparin groups than in the no-anticoagulation group (6.2 percent). A cause-and-effet relationship between the use of anticoagulants and flap loss or prevention of thrombosis could not be established. We can conclude, however, that the use of low-dose heparin does not increase significantly the risk of hematoma or intraoperative bleeding.
