Polyvinylidene Fluoride as a Suture Material: Evaluation of Comet Tail-Like Infiltrate and Foreign Body Granuloma.

BACKGROUND: Biocompatibility and tissue integration of a surgical suture are decisive factors for wound healing and therefore for the success of sutures. The optimal suture material is still under discussion. Polyvinylidene fluoride (PVDF) is described to have superior properties of biocompatibility and is therefore frequently used as a mesh component. Only little information is available about its use as a suture material. The aim of this study was to evaluate the biocompatibility of PVDF as a suture material in comparison to 5 different established sutures in a rat model. METHODS: In 30 male rats, a monofilamental PVDF suture (Resopren®) and 5 established control suture materials [polyester (Miralene®), polytetrafluoroethylene (Gore®), poliglecaprone (Monocryl®), polydioxanone (Monoplus®), polyglactin 910 (Vicryl®), USP size 3-0] were placed in the subcutaneous layer of the abdominal wall without knot or tension. After 3, 7 or 21 days, the abdominal walls were explanted for histopathological and immunohistochemical investigation with special regard to the size and quality of foreign body granuloma and the length of the comet tail-like infiltrate (CTI). RESULTS: The PVDF sutures showed the smallest size of foreign body granuloma (60 ± 14 µm) and the smallest CTI length (343 ± 60 µm) of all polymers after 21 days. Only PVDF (Resopren) and polydioxanone (Monoplus) showed a significant collagen I/III ratio increase between days 3 and 21 (p = 0.009 and p = 0.016). The quality of foreign body reaction regarding inflammation, proliferation and fibrotic remodeling was similar between all suture materials. CONCLUSIONS: Our data indicate that monofilamental PVDF sutures show a favorable foreign body reaction with small granuloma sizes and CTI length in comparison to established sutures. Its use as a suture material in general surgery could therefore be extended in the future. To reinforce these findings, further clinical studies need to be conducted.

Intraperitoneally applied gentamicin increases collagen content and mechanical stability of colon anastomosis in rats.

BACKGROUND: Anastomotic leakage remains a serious complication in colorectal surgery, and is being caused by a multitude of factors. Recent reports reveal changes of the extracellular matrix as risk factors as well as gentamicin as a potential agent to influence wound healing. This experimental study was initiated to investigate the influence of intraperitoneally applied gentamicin on colonic anastomotic wound healing and in particular on mechanical stability, overall collagen content and collagen type I/III ratio. MATERIALS AND METHODS: Sixty Sprague Dawley rats were randomized to one of two groups. In each animal, a standard transverse colonic end-to-end anastomosis was performed. Immediately postoperative, either 5 ml gentamicin (1 ml/kg bodyweight) or NaCl 0.9% was applied intraperitoneally. On postoperative days 3, 5, and 14, ten of the animals in each group were sacrificed. Measurements of the anastomosis bursting pressure were performed on postoperative days 3 and 5. At each explantation time, the collagen per protein ratio, the collagen types I/III ratio, and both the expression of MMP-2, -9, and Ki67 were analyzed. RESULTS: None of the animals died. None of the rats exhibited clinical evidence of anastomotic leakage. The bursting strength in the gentamicin group was significantly elevated on postoperative day 5. Both the overall collagen content and the collagen type I/III ratio in the gentamicin group were significantly increased 3, 5, and 14 days postoperatively compared to the control group. The expression of MMP-9 was significantly elevated in the gentamicin group both 3 and 5 days postoperatively. In contrast, there were no significant differences in the expression of MMP-9 14 days postoperatively. All investigated samples demonstrated positive staining for MMP-2 and Ki67 without statistically significant differences at any term, respectively. CONCLUSIONS: The present data confirm that intraperitoneally applied gentamicin is able to enhance healing and stability of colonic anastomosis due to an increase of both the overall collagen content and collagen type I/III ratio.

Different tissue reaction of oesophagus and diaphragm after mesh hiatoplasty. Results of an animal study.

BACKGROUND: Laparoscopic mesh-reinforcement of the hiatal region in the treatment of gastroesophageal reflux disease (GERD) and paraesophageal hernia (PEH) reduces the risk of recurrence. However, there are still controversies about the technique of mesh placement, shape, structure and material. We therefore compared tissue integration and scar formation after implantation of two different polypropylene-meshes in a rabbit model. METHODS: A total of 20 female chinchilla rabbits were included in this study. Two different meshes (Polypropylene PP, Polyglecaprone 25 Composite PP-PG) were implanted on the abdominal diaphragm around the oesophagus. After 3 months the implanted meshes were excised en-bloc. Histological and morphological analyses were carried out accordingly proliferation rate, apoptosis and collagen type I/III ratio. RESULTS: Regarding proliferation rate of oesophagus PP (9.31 +/- 3.4%) and PP-PG (13.26 +/- 2.54%) differ in a significant (p = 0.0097) way. In the diaphragm we found a significant (p = 0.00066) difference between PP (9.43 +/- 1.45%) and PP-PG (18.73 +/- 5.92%) respectively. Comparing oesophagus and diaphragm we could prove a significant difference within PP-PG-group (p = 0.0195). Within PP-group the difference reached no statistical significance (p = 0.88). We found analogous results regarding apoptosis.Furthermore, there is a significant (p = 0.00013) difference of collagen type I/III ratio in PP-PG (12.28 +/- 0.8) compared to PP (8.44 +/- 1,63) in case of oesophageal tissue. Concerning diaphragm we found a significant difference (p = 0.000099) between PP-PG (8.85 +/- 0.81) and PP (6.32 +/- 1.07) as well. CONCLUSION: The histologic and morphologic characteristics after prosthetic enforcement of the hiatus in this animal model show a more distinct tissue integration using PP-PG compared to PP. Additionally, different wound healing and remodelling capability influence tissue integration of the mesh in diaphragm and oesophagus.

New polymer for intra-abdominal meshes--PVDF copolymer.

PURPOSE: Full tissue integration without adhesion formation is still a challenge for intra-abdominal mesh materials. Purpose of this study was to investigate the adhesive potential and fibrocollagenous ingrowth of a polymer blend of polyvinylidene fluoride and hexafluorpropylene (co-PVDF), an established suture material in vascular surgery, when placed as a mesh in the intra-abdominal position. The results were compared with a matching polypropylene (PP) mesh. METHODS: In an established rabbit model, mesh implantation was performed by laparoscopy in the intraperitoneal onlay mesh technique. After 7, 21, and 90 days the degree of adhesion formation, foreign body reaction, bridging, and shrinkage of mesh area were investigated. RESULTS: In the early phase after 7 and 21 days we found significantly more adhesions for PP, but no differences after 90 days. Analysis of tissue reaction showed a significantly lower fibrotic reaction for co-PVDF. The degree of shrinkage revealed no significant difference. CONCLUSION: Large-pore PP and co-PVDF-meshes showed comparable good results in the intra-abdominal position, with a reduced inflammatory tissue reaction for co-PVDF. Large pore meshes should be considered an alternative for the development of intraperitoneal onlay meshes.

Missing effects of zinc in a porcine model of recurrent endotoxemia.

BACKGROUND: Chronic human sepsis often is characterised by the compensatory anti-inflammatory response syndrome (CARS). During CARS, anti-inflammatory cytokines depress the inflammatory response leading to secondary and opportunistic infections. Proved in vitro as well as in vivo, zinc's pro-inflammatory effect might overcome this depression. METHODS: We used the model of porcine LPS-induced endotoxemia established by Klosterhalfen et al. 10 pigs were divided into two groups (n = 5). Endotoxemia was induced by recurrent intravenous LPS-application (1.0 microg/kg E. coli WO 111:B4) at hours 0, 5, and 12. At hour 10, each group received an intravenous treatment (group I = saline, group II = 5.0 mg/kg elementary zinc). Monitoring included hemodynamics, blood gas analysis, and the thermal dilution technique for the measurement of extravascular lung water and intrapulmonary shunt. Plasma concentrations of IL-6 and TNF-alpha were measured by ELISA. Morphology included weight of the lungs, width of the alveolar septae, and rate of paracentral liver necrosis. RESULTS: Zinc's application only trended to partly improve the pulmonary function. Compared to saline, significant differences were very rare. IL-6 and TNF-alpha were predominately measured higher in the zinc group. Again, significance was only reached sporadically. Hemodynamics and morphology revealed no significant differences at all. CONCLUSION: The application of zinc in this model of recurrent endotoxemia is feasible and without harmful effects. However, a protection or restoration of clinical relevance is not evident in our setting. The pulmonary function just trends to improve, cytokine liberation is only partly activated, hemodynamics and morphology were not influenced. Further pre-clinical studies have to define zinc's role as a therapeutic tool during CARS.

Postoperative peridural analgesia increases the strength of colonic contractions without impairing anastomotic healing in rats.

BACKGROUND AND AIMS: Peridural analgesia (PDA) is a common treatment in postoperative management after abdominal surgery to shorten postoperative ileus and to permit early postoperative nutrition. There are conflicting opinions on the effect of early peristalsis on healing of colonic anastomoses. PATIENTS AND METHODS: A short segment of the distal colon was resected in 32 Wistar rats. Two strain gauge transducers were placed on the serosa proximal to the anastomosis to measure the strength and periodicity of bowel contractions. A peridural catheter was placed between lumbar vertebra 7 and the sacral crest. The animals received 4, 16, 20, and 24 h after operation an injection of either 0.03 ml ropivacaine 0.75%/kg body weight or the same amount of sodium chloride (controls). After 3 and 10 days the colonic anastomoses were resected to measure the bursting pressure. The anastomoses were prepared for histopathological examination and determination of relative collagen content. RESULTS: Postoperative PDA led to an increasing amplitude of phasic and tonic contractions while the frequency of contractions was not significantly affected. None of the groups presented with any anastomotic complications. The bursting pressure after 3 and 10 days was similar in the two groups. The relative amount of collagen I in the anastomotic area was significantly higher after treatment with peridural ropivacaine. CONCLUSION: Postoperative PDA with ropivacaine increases the strength of colonic contractions. The increase in phasic contractions suggests a better propulsive bowel function. The significantly higher amount of collagen I in the anastomosis of animals in the PDA group supports the idea that healing of colonic anastomoses is improved rather than diminished by PDA.

Influence of postoperative epidural analgesia with bupivacaine on intestinal motility, transit time, and anastomotic healing.

Epidural application of bupivacaine has been suggested to have a sympatholytic effect on spinal reflex mechanisms that shortens postoperative paralysis and leads to an improved transit time. The influence on anastomitic healing remains controversial. Laparotomy was performed in eight dogs. A short segment of the distal colon was resected and five electrodes were fixed on the serosa to measure the myoelectric activity (e.g., Migrating Myoelectric Complex--MMC). After operation a peridural catheter was placed between L7 and the sacral crest. One milliliter of bupivacaine 0.25% for each 3 kg of body weight was injected every 4 hours. Barium pellets coated in wax were placed into the stomach to allow radiographic representation of transit time. After 5 days the colon anastomosis was resected to measure the bursting pressure. In the peridural analgesia group (PDA) we found one small bowel intussusception and one covered anastomotic leakage. Postoperative PDA led to early and severe myoelectric activity but did not influence the time until the first MMC occurred (44 +/- 0.8 h, PDA; 44.6 +/- 1.5 h,control). Neither the transit time to the colon (50.2 +/- 1.9h, PDA; 51.7 +/- 5.5 h, control) nor the anastomotic healing was influenced (bursting pressure: 176 +/- 21.1 mmHg, PDA; 152 +/- 27.7 mmHg, control). Postoperative epidural analgesia with bupivacaine shortens intestinal paralysis. Early myoelectric activity with a lack of propulsive activity can cause complications like small bowel intussusception. Hence early postoperative enteral nutrition after epidural analgesia is risky. Because the influence of epidural analgesia on propulsive motility remains unclear, it seems reasonable to recommend its limited use in colon surgery.