Permacol interposition graft as an alternative to vein in contaminated wounds using a rabbit model.

BACKGROUND: Vascular injuries are common in trauma and often involve massive soft tissue injury and segmental arterial loss. Current practice uses either autogenous vein or polytetrafluorethylene (PTFE) for interposition grafting in arterial injuries. Decision making between autogenous or synthetic conduit pivots around the physiological state of the trauma patient. Vein is known to increase operative times in an already physiologically depleted patient, whereas synthetic graft can be simply pulled from the shelf. However, when used in contaminated wounds, PTFE is prone to chronic infection and subsequent graft failure. An alternative synthetic conduit resistant to infection would be ideal for such situations. Permacol (Tissue Science Laboratories, Inc, Andover, MA), a biosynthetic material, has demonstrated resistance to bacterial contamination in contaminated hernia repairs. When fashioned into a tubular structure, this material may be useful as an alternative vascular conduit in contaminated trauma wounds. METHODS: New Zealand white rabbits were randomized to one of 4 groups: Permacol graft (P) without bacterial contamination (n = 9), Permacol graft with bacterial contamination (CP; n = 9), autogenous vein graft without bacterial contamination (V; n = 9), or autogenous vein with bacterial contamination (CV; n = 9). All groups then underwent interposition grafting of the right common carotid artery. Grafts were contaminated by applying Staphylococcus aureus (1 × 10(5) colonies/0.1 mL) directly to the exposed surface of the graft on completion of the arterial repair. Each graft was then excised at day 42, and segments were collected for histologic evaluation, bacterial counts, and real-time polymerase chain reaction. RESULTS: Of the 36 rabbits used in this study, 3 animals in the CV group died within 72 hr of surgery. There was no difference in early mortality between P and V (0% vs. 0%; P = 1.0); however, early mortality was higher in the CV compared with the CP group (33% vs. 0%; P = 0.023). At 42 days, histologic evaluation of graft patency demonstrated no difference between P and V (67% vs. 33%; P = 0.157); however, patency was higher in CP than CV (56% vs. 12%; P = 0.040). In addition, no difference was found between the 2 contaminated groups in regard to the number of bacteria present on each graft material. CONCLUSIONS: Permacol as an interposition graft is a feasible alternative to vein in a contaminated setting and shows resistance to infection in a rabbit model. Future studies are needed to evaluate this material in larger animal models.

The effect of hyperbaric oxygen on nitric oxide synthase activity and expression in ischemia-reperfusion injury.

BACKGROUND: Hyperbaric oxygen (HBO) mitigates ischemia-reperfusion (IR) injury via a nitric oxide mechanism that is nitric oxide synthase (NOS) dependent. The purpose of this study was to investigate this NOS-dependent mechanism by examining isoform-specific, tissue-specific, and time-specific upregulation of NOS mRNA, protein, and enzymatic activity. METHODS: We raised a gracilis flap in Wistar rats that were separated into early and late phases. Treatment groups included nonischemic control, IR, HBO-treated ischemia-reperfusion (IR-HBO), and nonischemic HBO control. We harvested tissue-specific samples from gracilis, rectus femoris, aorta, and pulmonary tissues and processed them by reverse transcription polymerase chain reaction and Western blot to determine upregulation of isoform-specific NOS mRNA and protein. We also harvested tissue for NOS activity to investigate upregulation of enzymatic activity. Data are presented as mean ± standard error of the mean with statistics performed by analysis of variance. P ≤ 0.05 was considered significant. RESULTS: There was no increase in NOS mRNA in the early phase. In the late phase, there was a significant increase in endothelial-derived NOS (eNOS) mRNA in IR-HBO compared with IR in gracilis muscle (79.4 ± 22.3 versus 36.1 ± 4.5; P < 0.05) and pulmonary tissues (91.0 ± 31.2 versus 30.2 ± 3.1; P < 0.01). There was a significant increase in the late-phase eNOS pulmonary protein IR-HBO group compared with IR (235.5 ± 46.8 versus 125.2 ± 14.7; P < 0.05). Early-phase NOS activity was significantly increased in IR-HBO compared with IR in pulmonary tissue only (0.049 ± 0.009 versus 0.023 ± 0.003; P < 0.05). CONCLUSIONS: The NOS-dependent effects of HBO on IR injury may result from a systemic effect involving an early increase in eNOS enzymatic activity followed by a late-phase increase in eNOS protein expression within the pulmonary tissues.

Anorectal abscess and fistula-in-ano: evidence-based management.

The management of anorectal abscess and anal fistula has changed markedly with time. Invasive methods with high resulting rates of incontinence have given way to sphincter-sparing methods that have a much lower associated morbidity. There has been an increase in reports in the medical literature describing the success rates of the varying methods of dealing with this condition. This article reviews the various methods of treatment and evidence supporting their use and explores advances that may lead to new therapies.