Jessica J. Heath

The Addition of Lysostaphin Dramatically Improves Survival, Protects Porcine Biomesh from Infection, and Improves Graft Tensile Shear Strength

BACKGROUND Lysostaphin (LS), a naturally occurring Staphylococcal endopeptidase, has the ability to penetrate biofilm, and has been identified as a potential antimicrobial to prevent mesh infection. The goals of this study were to determine if LS adhered to porcine mesh (PM) can impact host survival, reduce the risk of long-term PM infection, and to analyze lysostaphin bound PM (LS-PM) mesh-fascial interface in an infected field. METHODS Abdominal onlay PMs measuring 3×3 cm were implanted in select groups of rats (n=75). Group assignments were based on bacterial inoculum and presence of LS on mesh. Explantation occurred at 60 d. Bacterial growth and mesh-fascial interface tensile strength were analyzed. Standard statistical analysis was performed. RESULTS Only one out of 30 rats with bacterial inoculum not treated with LS survived. All 30 LS treated rats survived and had normal appearing mesh, including 20 rats with a bacterial inoculum (10(6) and 10(8) CFU). Mean tensile strength for controls and LS and no inoculum samples was 3.47±0.86 N versus 5.0±1.0 N (P=0.008). LS groups inoculated with 10(6) and 10(8) CFU exhibited mean tensile strengths of 4.9±1.5 N and 6.7±1.6 N, respectively (P=0.019 and P<0.001 compared with controls). CONCLUSION Rats inoculated with S. aureus and not treated with LS had a mortality of 97%. By comparison, LS treated animals completely cleared S. aureus when challenged with bacterial concentrations of 1×10(6) and 1×10(8) with maintenance of mesh integrity at 60 d. These findings strongly suggest the clinical use of LS-treated porcine mesh in contaminated fields may translate into more durable hernia repair.

Collagen–elastin ratio predicts burst pressure of arterial seals created using a bipolar vessel sealing device in a porcine model

BackgroundBipolar electrosurgical devices are used to generate rapid and efficient hemostasis in a wide range of surgical procedures. Of the factors that influence seal integrity, vessel (artery) diameter has been considered the most important variable. In this study we hypothesized that the relative ratio of the components that form the seal (collagen and elastin) determine the degree of vessel distensibility and play an equally important role in defining seal strength.MethodsPorcine carotid, renal, iliac, and femoral arteries were sealed using a bipolar electrosurgical device in vivo. Following removal, arterial diameter was measured and vessels’ seals tested for arterial burst pressure (ABPr). Samples were then analyzed histologically and biochemically for collagen and elastin content.ResultsArteries with the highest collagen–elastin ratio (C/E) (renal) consistently demonstrated significantly higher burst pressures than those arteries with lower C/E ratios (iliac and femoral) independent of artery diameter.ConclusionUsing arteries of distinct anatomical origin and physiological function, we demonstrate that total collagen content, and more specifically C/E ratio, in porcine arteries is a more accurate predictor of ABPr than vessel size alone.

Guidelines for Power and Time Variables for Microwave Ablation in an In Vivo Porcine Kidney

PURPOSE Microwave technology provides an emerging thermal ablation technique for solid organ tumors. We propose guidelines and recommend optimal time and power for use. METHODS Microwave ablations using a VivaWave Microwave Ablation System (Valleylab, Boulder, CO) were performed in vivo in a porcine kidney model. The independent variables were power (20, 30, 40, 45, 50, 60 W) and time (2, 4, 6, 8, 10, 15, 20 min) with the outcome variable diameter of ablation. Following ablations, kidneys were procured for gross and histological evaluation. Analysis of variance (ANOVA) was used followed by Tukey tests when appropriate. A P value of <0.05 was considered statistically significant. RESULTS In 308 total ablations, a minimum of 7 ablations were performed in 35 of 42 power and time variables (83%). The outcome variable, ablation diameter, was affected significantly by time, power, and time/power interaction (P < 0.0001). For each time point, a one-way ANOVA showed an overall significant difference in ablation size X wattage (P < 0.0001). Tukey tests showed that, at each time point, ablation sizes at 45, 50, and 60 W were not significantly different. After determining that 45 W was optimal, a one-way ANOVA showed an overall significant difference in ablation sizes for time points at 45 W (P < 0.0001). Tukey tests showed that, at 45 W, ablation sizes at 10 min were significantly larger than ablation sizes at 8, 6, 4, and 2 min. CONCLUSIONS We propose guidelines for use of a novel microwave ablation system and recommend use at 45 W for 10 min.

An evaluation of electrosurgical vessel-sealing devices in biliary tract surgery in a porcine model

OBJECTIVES The purpose of this study was to evaluate two electrosurgical vessel-sealing devices in biliary surgery. METHODS Porcine common bile ducts (CBDs) were sealed with two electrosurgical devices, an electrothermal bipolar vessel-sealing device (EBVS) and ultrasonic coagulation shears. Acute study animals underwent surgical bile duct sealing followed by immediate burst pressure testing. Chronic study animals were maintained for 1 week postoperatively and then tested. RESULTS The seal failure rate in the acute study was 50% for both the EBVS device and shears, and 0% for the laparoscopic surgical clip device used as a control. The latter had significantly higher burst pressures (646.2 ± 281.8 mmHg; P = 0.006) than the EBVS device (97.6 ± 86.6 mmHg) and shears (71.7 ± 89.3 mmHg). No significant difference in burst pressures was noted between the EBVS device and shears (97.6 ± 86.6 mmHg vs. 71.7 ± 89.3 mmHg). In the chronic study, obvious bile leaks occurred in one of four pigs (25%) in the EBVS device subgroup and two of four pigs (50%) in the shears subgroup. The average proximal CBD pressure in seven pigs was 16.1 ± 4.1 mmHg. The average chronic burst pressure in the control subgroup was 1088.0 ± 922.6 mmHg. CONCLUSIONS Given the high rates of failure of the EBVS device and the shears in consistently sealing biliary ducts, we do not recommend their routine use in biliary surgery.

Evaluation of composite mesh for ventral hernia repair.

Composite mesh was associated with minimal intraabdominal adhesions, progressive in-growth of host tissue, and complete degradation of an internal polydioxanone ring that was of assistance in mesh positioning.

Analysis of cell death and vertebral end plate bone mineral density in the annulus of the aging sand rat

BACKGROUND CONTEXT The relationship between disc degeneration and end plate sclerosis is poorly understood. The sand rat is an excellent, economical small-animal model in which disc degeneration is age related, spontaneous, reliable, and well characterized. This model is used here to evaluate disc degeneration, disc cell viability, and vertebral end plate bone mineral density (BMD) in lumbar sites. PURPOSE To determine the proportion of live and dead cells and end plate bone mineral density in the aging sand rat annulus. STUDY DESIGN Young and old sand rats were used in work approved by the Institutional Animal Care and Use Committee. Outcome measures were the percentage of live/dead annulus cells in the disc and the BMD of cranial and caudal end plates of lumbar vertebrae. METHODS Bone densitometry was used to obtain endplate BMD on lumbar spines of 16 young sand rats aged 2 to 6 months and 26 older animals aged 22 to 46 months. X-ray films were analyzed for wedging, end plate calcification, and disc-space narrowing. Additional discs were also harvested and incubated with fluorochromes, and the percentage of live or dead cells were determined for the outer, inner annulus, and entire annulus. RESULTS Radiographically old animals had significantly greater incidence of lumbar wedging (p<0.004) and a significantly greater incidence of end plate calcification and disc-space narrowing (p<0.01). In the live-dead study, the mean percentage of dead annulus cells for the three age groups were significantly different for the outer annulus (p<0.001), inner annulus (p=0.005), and total annulus (p<0.0001). The percentages of dead cells for the entire annulus were 46.14%+/-7.99% (age 2-6 months), 48.13%+/-17.32% (age, 13-19 months), and 76.80%+/-7.27% (age 26-38 months). The percentage of dead disc cells correlated significantly with age for outer annulus, inner annulus, and total annulus (p<0.006). The percentage of dead cells in the entire annulus and the inner annulus correlated significantly with end plate BMD (p<0.02). CONCLUSIONS Data are novel and show that in very aged sand rats, end plate BMD is significantly greater than that of young animals. Live/dead cell analyses showed increasing cell death in both outer and inner annulus, which correlated significantly with age and with end plate BMD.

Effect of Bacterial Exposure on Acellular Human Dermis in a Rat Ventral Hernia Model

BACKGROUND Effectiveness of acellular human dermis (AHD) as an alternative to synthetic mesh in contaminated fields has been described. Cellular migration after implantation and corresponding strength of attachment is not well documented. Our aim is to correlate AHD vascularization, fibroblast migration, and strength of attachment with presence of inflammatory cells in clean and contaminated fields. MATERIALS AND METHODS Lewis rats were randomized to a control and three experimental groups. AHD was placed as an onlay over the intact abdominal wall. Experimental groups (n=72) were exposed to Staphylococcus aureus at 1 x 10(4), 1 x 10(5), or 1 x 10(6) by direct application; controls (n=12) were not exposed. At 5 and 28 d, abdominal walls were explanted and tissue ingrowth assessed via tensiometry measuring energy (E) and max stress (MS) at the AHD-tissue interface. Vascularity, fibroblast migration, and inflammatory cell migration were compared using light microscopy. RESULTS Shear strength reported as energy and max stress were significantly greater at 28 versus 5 d in all experimental groups, remaining unchanged in controls. Plasma cells and histiocytes significantly increased in all groups; macrophages increased in experimental groups only. Vascular ingrowth increased significantly in all groups; fibroblast migration was greater in controls and 1 x 10(6) exposed group only. CONCLUSIONS Contamination of AHD results in inflammatory cell influx and a surprising increase in shear strength. Interestingly, shear strength does not increase without contamination. Inflammation stimulates vascular ingrowth, but not equally significant fibroblast migration. Longer survivals are required to determine if energy and max stress of controls increase, and fibroblast migration follows vascular ingrowth.

Patient out-of-pocket expenses in major orthopedic procedures: total hip arthroplasty as a case study.

Total hip arthroplasty (THA) is a successful procedure for improving quality of life. There are few publications regarding out-of-pocket expenses incurred by individuals undergoing uncomplicated THA. Detailed billing and record reviews and patient phone surveys were conducted on 34 Medicare patients identifying charges and reimbursements recorded by the health care system and all out-of-pocket expenses incurred by patients undergoing uncomplicated THA (diagnostic related group [DRG] 209/current procedural terminology [CPT] 27130). Mean THA total billed charges were

The effect of preoperative corticosteroids on peritoneal macrophage function after laparoscopic and open abdominal surgery in a rat model

46378, 89% of that from inpatient hospitalization and 5% incurred preoperatively and 7% postoperatively. Medicare reimbursement was

Evaluation of Soft Tissue Attachments to a Novel Intra-abdominal Prosthetic in a Rabbit Model

14647, supplemental reimbursement was