The use of anticoagulants to prevent deep venous thrombosis and pulmonary embolism following surgery for abdominal aortic aneurysm

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.

Authors' conclusions: 

There is not enough evidence to make a definitive conclusion about the use of anticoagulant drugs (with or without mechanical devices) for DVT prophylaxis in patients undergoing abdominal aortic surgery.

Read the full abstract...

Deep vein thrombosis (DVT) is one of the most common, preventable complications of surgery. Although the relationship between surgery and DVT is well established in general surgical operations and most other subspecialties, the same cannot be said about arterial surgery. Deep vein thrombosis is believed to be less common in aortic surgery where its management is rather controversial with a reported incidence of DVT from 2% to 18%.

Intra-operative heparin is believed to provide protection during the period when DVT is most likely to develop. The practice of using intra-operative heparin could increase the risk of haemorrhagic complications if further heparin is used during the recovery period. This can significantly limit the use of such prophylactic measures especially with the low perceived risk of venous thromboembolism (DVT or pulmonary embolism (PE)) following abdominal aortic surgery. However, vascular patients are usually older, with more co-morbidity and are subject to prolonged immobility, all of which increase the likelihood of developing venous thromboembolism. This is an update of the Cocharane review published in 2008.


To determine the efficacy of anticoagulant prophylaxis (with or without mechanical devices) in patients undergoing surgery for abdominal aortic aneurysm.

Search strategy: 

The Cochrane Peripheral Vascular Diseases Group searched their trials register (last searched 13 July 2009) and the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, (last searched Issue 3, 2009).

The authors searched for additional trials through reference lists of retrieved studies and conference proceedings.

Selection criteria: 

Randomised controlled trials comparing the use of anticoagulants (with or without mechanical devices) with control or no intervention in preventing DVT or PE after abdominal aortic operations.

Data collection and analysis: 

Three authors independently selected potential trials and assessed trial quality.

Main results: 

Two studies (n=147) were included. Both studies had methodological limitations.

There were no data to indicate that post operative anticoagulation, with or without the use of mechanical devices, can safely reduce the incidence of DVT after aortic surgery. Neither study reported a significant effect of anticoagulants on the incidence of PE or related mortality. One study was terminated before recruiting sufficient participants due to a higher incidence of bleeding while using anticoagulants. The incidence of minor bleeding events was slightly higher with anticoagulants.