Summary
In a prospective, double-blind, randomized multicenter trial the efficacy and safety
of low molecular weight heparin and unfractionated heparin were compared for the prevention
of postoperative deep vein thrombosis in patients undergoing abdominal surgery. Six
hundred and seventy-three patients were randomly allocated to the two prophylaxis
groups; 20 of these, however, did not undergo surgery and did not receive any prophylaxis.
Of the remaining 653 patients 323 received one subcutaneous injection of 3,000 anti-Xa
units of low molecular weight heparin and 330 received subcutaneously 5,000 U heparin
three times a day. Treatment was initiated 2 h preoperatively and continued for 7
to 10 days. The occurrence of DVT was determined by the 125I-labelled fibrinogen uptake test and phlebography. Venous thrombosis was diagnosed
in 24 of 323 patients (7.4%) treated with low molecular weight heparin and in 26 of
330 patients (7.9%) treated with low-dose heparin. DVT of proximal veins was detected
in four patients of the low molecular weight heparin group and in three patients of
the low-dose heparin group. During the observation period three pulmonary emboli -
one fatal and two non-fatal - occurred in patients receiving prophylaxis with low-dose
heparin. No pulmonary embolism was found in patients treated with low molecular weight
heparin. Both prophylactic schemes were well tolerated. Intra-and postoperative blood
loss, incidence of wound hematoma, frequency and volume of intra- and postoperative
blood transfusion were similar in both groups with a slight advantage for the low
molecular weight heparin group. The results of this trial show that the investigated
low molecular weight heparin is at least as effective and safe as low-dose heparin
in preventing deep vein thrombosis in patients undergoing elective abdominal surgery.
