Twenty-three studies were combined for review (n=2,382 patients); 17 prospective non-randomised studies (n=1,570 patients) and six RCTs (n=812 patients). Methodological quality was not assessed, but potential for bias in some study designs was noted in the text, including the inclusion of patients with preoperative deep vein thrombosis, the inclusion of patients receiving anti-coagulants preoperatively, and the use of tests with high false positive rates to detect deep vein thrombosis.
When only prospective non-randomised studies were considered, the deep vein thrombosis rate ranged from 0% to 20.5% in patients undergoing aortic surgery (seven studies, n=407 patients), from 2.5% to 41% in patients undergoing general arterial surgery surgery (four studies, n=114 patients), from 2.8% to 8% in patients undergoing peripheral non-arterial surgery (three studies, n=531 patients) and from 0% to 14.3% in patients with amputations (three prospective non-randomised studies, n=167 patients).
Results on the effectiveness of prophylactic anticoagulants were mixed. One RCT' of patients undergoing general vascular surgery, reported no significant difference in the incidence of deep vein thrombosis between the group receiving anti-coagulants (12.5%) and the control group (10.5%) based on a total of 43 patients; as did one RCT of patients undergoing aortic surgery (both 2%) based on 98 patients. One RCT of patients undergoing aortic surgery reported an incidence of deep vein thrombosis of 24% in the control group compared to 8% in the low molecular weight heparin group (n=49 patients). The results comparing different types of anti-coagulants were also reported.
The incidence of pulmonary embolism ranged from 0% to 2.3%, with an overall incidence rate of 0.4%, based on a total of 1,848 patients. Mortality from pulmonary embolism ranged from 0% to 6.3% with an overall pulmonary embolism mortality of 0.1%. Twenty-one studies did not report any incidents of major bleeding. The incident rate for major bleeds in the other two studies was 2.7% and 2.5%