Low molecular mass heparin instead of unfractionated heparin during infrainguinal bypass surgery

To test whether low molecular mass heparin (LMMH) is comparable to unfractionated heparin (UFH) as an anticoagulant during infrainguinal bypass surgery and to investigate laboratory evidence of hypercoagulation in patients undergoing infrainguinal bypass surgery.

Eighteen patients were randomised to receive either UFH or LMMH (70 anti-Xa units/kg b.w.). Soluble fibrin, measured as fibrin monomers (FM) and fibrinopeptide A (FPA), were measured in blood from the femoral vein before, during and after release of the occluding clamps during surgery. In addition, fibrinogen prothrombin complex, thrombin-antithrombin complex, platelets and antithrombin were measured before surgery. Heparin levels (Anti Xa) were measured during surgery.

Increased levels of fibrinogen, FPA, thrombin antithrombin complex and FM were recorded prior to surgery. During surgery no further increase was noted. The anti Xa levels were slightly higher in patients with LMMH than in patients receiving UFH. Levels of FM were significantly lower in patients receiving LMMH. No difference in FPA was noted. A positive correlation between fibrinogen and FPA and FM respectively was recorded. Four patients, two in each group, were reoperated for graft occlusion. One patient in the UFH group required reoperation because of bleeding.

LMMH is comparable to UFH as an anticoagulant during infrainguinal bypass surgery. Variables reflecting hypercoagulability are elevated in this group of patients and are positively correlated to the fibrinogen level. High fibrinogen levels could thus be a risk for perioperative thrombosis.