Antibiotic-loaded polymethylmethacrylate beads for the treatment of extracavitary vascular surgical site infections.

OBJECTIVE: This study assessed the efficacy of antibiotic-loaded polymethylmethacrylate (PMMA) beads in the treatment of lower extremity vascular surgical site infections (VSSIs). METHODS: This was a retrospective review of all patients with a VSSI of a lower extremity bypass treated with antibiotic-loaded PMMA beads and culture-specific antibiotics during a 4.5-year period. Data collected included patient demographics, comorbidities, site of initial graft infection, symptoms and signs at presentation, initial and additional surgical debridement, wound culture results, type of antibiotic beads implanted, and graft treatment strategy, comprising conduit preservation or in situ replacement, with associated soft tissue management by muscle flap or vacuum-assisted closure. Primary outcome measures included death, recurrent infection, and limb salvage. RESULTS: Forty patients developed 42 extracavitary lower extremity VSSIs (bilateral groin infections in two). Patients were treated according to our treatment algorithm with antibiotic-impregnated PMMA beads. Previous reconstructions included nine aortofemoral bypasses (groin infection only), 20 infrainguinal bypasses, five extra-anatomic bypasses, five femoral interpositions, two combined inflow-outflow bypass procedures, and one patch angioplasty with VSSI. Cultures isolated 59 pathogens (39 gram-positive, 18 gram-negative, 2 Candida spp). Methicillin-resistant Staphylococcus aureus was cultured from 10 VSSs (23.8%) overall and from 27.7% of those patients with attempted graft preservation or in situ reconstructions. Two patients (4.8%) had no growth despite clinical signs of infection. Repeat VSS exploration and culture results led to an average of 1.4 bead replacements before definitive treatment. Final treatment strategy included graft preservation of patent bypasses in 28, partial graft excision with in situ replacement in eight, graft removal only with residual graft remaining at implant site (ie, incorporated anastomotic conduit, 11.9%) in five, and extra-anatomic reconstruction in one. Sartorius muscle flap was performed in 14 groin infections (37.8%). The 30-day mortality was 0%, and limb loss was 7.1% (n = 3). At the median follow-up of 17 months, the limb loss was 21.4% and the recurrent infection rate was 19.4% (seven of 36) in those with attempted graft preservation or in situ replacement. CONCLUSIONS: Antibiotic-loaded PMMA beads may serve as an adjunct in the management of VSSIs and may also expand treatment options for graft preservation or in situ reconstruction, with expected recurrent infection rate approaching 20%. Further experience with this adjunct may help elucidate its role in the management of this complicated problem, including the need for bead exchanges, until perigraft cultures are free of microbes.

Detoxification in relation to toxin tolerance in desert woodrats eating creosote bush.

We studied the relationship between the use of three detoxification pathways and urine pH and the tolerance of desert woodrats from two populations to a mixture of naturally occurring plant secondary metabolites (mostly phenolics) in resin from creosote bush (Larrea tridentata). The two populations of desert woodrats came from the Mojave desert (Mojave woodrats), where woodrats consume creosote bush, and from the Great Basin desert (Great Basin woodrats), where the plant species is absent. We fed woodrats alfalfa pellets containing increasing levels of the phenolic resin and measured three detoxification pathways and urine pH that are related to detoxification of allelochemicals. We found that the excretion rate of two phase II detoxification conjugates, glucuronides and sulfides. increased with increasing resin intake, whereas excretion of hippuric acid was independent of resin intake, although it differed between populations. Urine pH declined with increasing resin ingestion. The molar proportion of glucuronides in urine was three times that of the other conjugates combined. Based on an evaluation of variation in the three detoxification pathways and urine pH in relation to resin intake, we rejected the hypotheses that woodrats' tolerance to resin intake is related to capacity for amination, sulfation, or pH regulation. However, Mojave woodrats had higher maximum glucuronide excretion rates, and we accepted the hypothesis that within and between populations woodrats tolerate more resin because they have a greater capacity for glucuronide excretion.