Predictors of prosthetic graft infection after infrainguinal bypass

Some patients require major leg amputation after lower-extremity prosthetic bypass for graft occlusion or failure of wound healing, despite a patent graft. Amputation above or below the knee was hypothesized to increase susceptibility to prosthetic graft infection in the ipsilateral extremity.

All patients undergoing implantation of prosthetic infrainguinal arterial bypass grafts identified from a vascular surgical registry during a 12-year period were reviewed. Patient demographic data, comorbid conditions, and operative details were evaluated as risk factors, with graft infection among the primary outcomes of interest.

Prosthetic graft infection occurred in 25 of 141 (18%) infrainguinal grafts and occurred most frequently after major amputation (41% versus 6%; odds ratio [OR] = 12; 95% CI, 4.1 to 34) or early reoperation after initial grafting (70% versus 16%; OR = 11; 95% CI, 1.9 to 63). Risk was highest after amputation within 4 weeks of bypass (70% versus 32%; OR = 5.0; 95% CI, 1.1 to 23). Graft thrombosis (84% versus 39%; OR = 8.3; 95% CI, 2.7 to 26) and presence of gangrene (52% versus 23%; OR = 3.6; 95% CI, 1.5 to 8.7) also increased infection risk. Independent predictors for development of graft infection were identified by stepwise regression analysis to be amputation (p < 0.001), early reoperation (p = 0.002), and absence of renal failure (p = 0.038) but not gangrene (p = 0.090). Amputations performed within 6 months of the initial bypass operation were more likely to be associated with prosthetic graft infection than those performed later than 6 months (52% versus 17%; OR = 5.3; 95% CI, 1.3 to 22).

Amputation increases risk of prosthetic graft infection, especially when performed early or after failed revascularization. Consideration should be given to partial or complete removal of a prosthetic graft above the level of the amputation under these conditions.