Optimization of rifampin coating on covered Dacron endovascular stent grafts for infected aortic aneurysms

In the treatment of an infected aorta, open repair and replacement with a rifampin-impregnated Dacron vascular graft decrease the risk of prosthetic graft infections, with several protocols available in the literature. We hypothesize that the same holds true for endovascular aneurysm repair, and after studying and optimizing rifampin solution concentration and incubation period to maximize the coating process of rifampin on Dacron endovascular stent grafts (ESGs), we propose a rapid real-time perioperative protocol.

Several prepared rifampin solutions, including a negative control solution, were used to coat multiple triplicate sets of Dacron endovascular aortic stent grafts at different but set incubation periods. Rifampin elution from the grafts was studied by spectroscopic analysis. Once an optimized solution concentration and incubation time were determined, the elution of rifampin over time from the graft and the graft's surface characteristics were studied by ultraviolet-visible spectroscopy and atomic force microscopy.

All coated ESGs with any concentration of prepared rifampin solution, regardless of incubation time, immediately demonstrated a visible bright orange discoloration and subsequently after elution procedures returned to the original noncolored state. At the 25-minute incubation time (standard flush), there was no statistical difference in the amount of rifampin coated to the ESGs with 10-mg/mL, 30-mg/mL, and 60-mg/mL solutions (0.06 ± 0.01, 0.07 ± 0.05, and 0.044 ± 0.01, respectively; P > .05). This was also true for a 10-minute incubation time (express flush) of 10-mg/mL and 60-mg/mL rifampin solution concentrations (0.04 ± 0.007 and 0.066 ± 0.014, respectively; P = .22). The elution-over-time of coated rifampin ESG, although not statistically significant, did seem to plateau and to reach a steady state by 50 hours and was confirmed by surface characteristics using atomic force microscopy.

Having studied two variables of rifampin coating techniques to Dacron ESGs, the authors propose a rapid real-time perioperative coating protocol by using a 10-mg/mL rifampin solution for a 10-minute incubation period. As rifampin loosely binds to Dacron ESGs by weak intermolecular forces, a rifampin-coated ESG would need to be inserted in a timely fashion to treat the diseased aorta and to deliver its antibiotic affect. A rapid perioperative coating protocol followed by immediate deployment makes our proposed technique especially useful in an urgent and unstable clinical scenario.