Deep vein thrombosis (DVT) is a preventable complication of surgery. The blood clot can break away and travel to the lungs to cause respiratory distress and death (pulmonary embolism). Deep vein thrombosis is believed to occur less often following aortic surgery than in general surgical operations because heparin used during most vascular operations may protect against intra-operative DVT. Vascular patients are usually older, with more co-morbidity (presence of other diseases or conditions), and are subject to prolonged immobility, which increase the likelihood of developing DVT. Bleeding (haemorrhagic) complications could however occur if further anticoagulants are used for DVT prophylaxis during recovery.
There were no data from randomised controlled trials to indicate that postoperative anticoagulation, with or without the use of mechanical devices, can safely reduce the incidence of DVT after abdominal aortic surgery. Only two randomised controlled trials that compared anticoagulants with control were found. Ninety-eight patients completed one study where one group was randomised to receive aggressive mechanical and pharmacological DVT prophylaxis while the other group did not receive any intervention. This study reported an equal DVT incidence of 2% in both groups. The trialists did not examine for calf DVT and considered it insignificant. An earlier study reported a high incidence of DVT (24% in the control group versus 8% in the heparin group) that did not reach statistical significance. All the confirmed DVT cases were in calf veins and only one case extended above the calf. The study used a regimen of calcium heparin 2500 U pre-operatively followed by 5000 U 12 hourly for seven days and was terminated early after recruiting only 49 participants because of eight cases of major bleeding. The other trial did not report any clinically-significant bleeding problems. Minor bleeding events including wound bruising and bleeding were reported in both included studies.