Balancing zinc deficiency leads to an improved healing of colon anastomosis in rats.

BACKGROUND: In colorectal surgery, anastomotic leakage is a relevant complication. The aim of this study was to investigate whether intraperitoneally (i.p.) administered zinc improves the healing of colon anastomosis in rats. MATERIALS AND METHODS: Male Wistar rats (66) received zinc-deficient diet for 21 days. To determine the effective dose of zinc which is necessary to compensate this deficiency, preliminary analysis in 30 rats were performed. In these rats, analysis by atom-absorption spectrophotometry revealed a dose of 1.0 mg zinc aspartate/kg body weight to be the compensatory dosage. In the remaining zinc-deficient rats (n= 36), a transverse colonic anastomosis was performed. Eighteen rats received either a zinc supplementation i.p. or 0.9% NaCl i.p. (n = 18; control group). On postoperative days 3, 5, and 14, the surface of the mucosal villi, expression of MMP 2, MMP 8, MMP 13, TIMP 1, as well as the collagen types I/III ratio were analyzed. RESULTS: Protein expression of MMP 2 and MMP 8 was significantly higher in the anastomosis of the zinc group on day 3 and on day 5. The collagen types I/III ratio was significantly increased in the zinc group on days 5 and 14. CONCLUSION: Balancing zinc deficiency benefits wound healing of colonic anastomosis qualitatively due to an increased collagen type I/III ratio. Surprisingly, these zinc supplements, however, increased the expression of MMP 2 and MMP 8 that are supposed to impair wound healing in case of an over-expression. Thus, further investigations are needed to elucidate the influence of zinc supplementation on regulation of MMPs.

Erythropoietin (EPO) influences colonic anastomotic healing in a rat model by modulating collagen metabolism.

INTRODUCTION: Anastomotic failure is one of the most frequent complications in abdominal surgery. During anastomotic healing. the strength of the intestinal tissue nearby is closely related to the accumulation of collagen in interlinked scar tissue. This in turn is influenced, among other things, by single groups of matrixmetalloproteinases, especially collagenases (MMP-1, -8, and -13) and gelatinases (MMP-2 and -9). EPO is known to induce the expression of tissue-inhibitor-of-matrixmetalloproteinases-1 (TIMP-1) and thereby to down-regulate MMPs. MATERIALS AND METHODS: We used a rat as an experimental model and applied a high dose of EPO (5U/g BW s.c.), one dose 24 h before operation (as pre-conditioning) and one dose directly after performing a colonic anastomosis. After 3 and after 5 d, respectively, immunohistochemical stainings for MMP-2, -8, and -9 as well as TIMP-1 were carried out and evaluated semiquantitatively for each layer of the colonic wall. Sirius-red staining and cross-polarization microscopy were evaluated and the collagen I/III ratio calculated. Anastomotic and colonic tissue distal to the anastomosis were used to determine collagen content. RESULTS: We found increased bursting pressure 5 d post-surgery after applying erythropoietin. It was thus shown that EPO influences collagen metabolism and changes the collagen I/III ratio in the colon distal to the anastomosis. The evaluation of immunohistochemistry did not show the expected ubiquitous up-regulation of TIMP-1 and down-regulation of MMPs. Nevertheless, correlations between TIMP-1, MMP-8, and collagen I/III ratio could only be established after the application of EPO. CONCLUSION: Contrary to our hypothesis, the picture of TIMP-1 and of the regulation of the MMPs after the application of EPO is not as clear as expected. EPO improves anastomotic bursting strength and the correlation of TIMP-1, MMP-8, and collagen type I/III ratio can only be seen after the application of EPO.

The influence of blood on the efficacy of intraperitoneally applied phospholipids for prevention of adhesions.

BACKGROUND: The formation of adhesions following abdominal surgery is a well known problem. In previous studies we demonstrated the efficacy and safety of intraperitoneally applied phospholipids in order to prevent adhesion formation. This study evaluates the influence of blood on the efficacy of intraperitoneally applied phospholipids for prevention of adhesions. METHODS: In 40 Chinchilla rabbits adhesions were induced by median laparotomy, standardized abrasion of the visceral and parietal peritoneum in defined areas of the ventral abdominal wall and the caecum. The animals were randomly divided into four groups. They received either phospholipids 3.0% or normal saline (NaCl 0.9%) (5 ml/kg body weight). In 50% of the rabbits we simulated intraperitoneal bleeding by administration of blood (1.5 ml/kg body weight). The other half served as control group. Ten days following the operation the animals were sacrificed and adhesion formation was assessed by computer aided planimetry and histopathologic examination. RESULTS: The median adhesion surface area in the NaCl-group (n = 9) amounted to 68.72 mm2, in the NaCl+Blood-group (n = 10) 147.68 mm2. In the Phospholipid (PhL)-group (n = 9) the median adhesion surface area measured 9.35 mm2, in the PhL+Blood-group (n = 9) 11.95 mm2. The phospholipid groups had a significantly smaller adhesion surface area (p < 0.05). CONCLUSION: Again these results confirm the efficacy of phospholipids in the prevention of adhesions in comparison to NaCl (p = 0.04). We also demonstrated the adhesion preventing effect of phospholipids in the presence of intraperitoneal blood.

Adhesion prevention comparing liquid and solid barriers in the rabbit uterine horn model.

OBJECTIVE: The purpose of this study was to assess the ability of four different either solid or fluid barriers to reduce adhesions in an established model of gynecological surgery. STUDY DESIGN: 50 Chinchilla rabbits underwent bilateral deperitonealization and devascularization of the uterine horns (DUH). Afterwards solid membranes of either hyaluronic acid-carboxymethylcellulose (HA-CMC) or lactide-caprolactone-copolymer (LCC) were placed around the injured uterine horns or fluids (icodextrin (ID) or phospholipids (PL)) were intraperitonealy administered. The control group went without protection. After 10 days, adhesions were measured by planimetry. RESULTS: Phospholipids (median 49.8 mm2) significantly reduced adhesion areas in comparison to all other groups: surgical controls (median 230.6 mm2), HA-CMC (median 194.9 mm2), LCC (median 327.1 mm2), and icodextrin (median 242.1 mm2). CONCLUSIONS: These results prove the efficacy of phospholipids to reduce primary adhesion formation in the Chinchilla double uterine horn model compared to HA-CMC, LCC and icodextrin. Future clinical studies are recommended.

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.

Phospholipids reduce adhesion formation in the rabbit uterine horn model.

OBJECTIVE: To access the ability of intraperitoneal phospholipids to reduce adhesions in a standardized model for gynecologic operations. DESIGN: A randomized, experimental, blinded study using the double uterine horn model. SETTING: Academic animal research laboratory. ANIMAL(S): Thirty-three Chinchilla rabbits. INTERVENTION(S): Phospholipids or Ringer's lactate were intraperitoneally administered after bilateral uterine horn injury. MAIN OUTCOME MEASURE(S): After 10 days, adhesions were evaluated concerning area and strength as well as scores describing tenacity and degree. RESULT(S): Phospholipids (median 102.1 mm2) significantly reduce adhesion areas in comparison to surgical controls (median 392.2 mm2) and Ringer group (median 323.8 mm2). Scores reflecting severity and degree of adhesions support this finding. CONCLUSION(S): These results prove the efficacy of phospholipids in the double uterine horn model. Future clinical studies are recommended.

Influence of early drainage of intraperitoneal phospholipids on efficacy of adhesion prevention.

Postoperative peritoneal adhesions impose a long-term risk of morbidity and mortality. Adjunctive means are needed to prevent these complications. In previous studies we could demonstrate the efficacy and safety of intraperitoneally applied phospholipids with regard to adhesion prevention and wound healing, respectively. The assumption is that phospholipids rapidly adhere to the peritoneal surface and to the mesothelial lesions. This study was designed to evaluate the influence of early drainage of the administered fluid volume on the control of adhesion formation. Forty chinchilla rabbits underwent median laparotomy and standardized abrasion of circumscript areas of the ventral abdominal wall, the cecum, and the ileum. The animals randomly received either 75 mg/kg body weight of phospholipids in a volume of 5.0 mL/kg body weight (n = 20) or the same volume of Ringer's lactate solution (n = 20) prior to closing the laparotomy wounds. In 50% of the rabbits with either medication, 80% of the volume was recovered after 30 min before final closure of the abdominal wall ("drainage"). In the remaining animals the intraabdominal fluid load was not evacuated ("no drainage"). At day 10 after surgery all rabbits were sacrificed for evaluation of adhesion areas by computer-aided planimetry and histopathologic examination. The mean areas of adhesion in both Ringer's lactate groups were significantly larger than in the comparable phospholipid groups (p < .05). In the Ringer's lactate groups, adhesions averaged 341.7 (318.6) mm2 without and 263.3 (275.5) mm2 with drainage. In the phospholipid groups the respective mean areas reached only 24.6 (36.7) mm2 without drainage and 27.0 (49.7) mm2 following evacuation of the fluid 30 min after administration (median, mean in parentheses). These results prove the efficacy of phospholipids after a limited contact period of 30 min. The frequent use of drains in abdominal surgery will not impair the beneficial effect of phospholipids on prevention of adhesions.

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.

Tension banding closure of laparotomies: results of an experimental study in dogs.

BACKGROUND: Conventional laparotomy closure may cause ischemia, edema, and necrosis of the incisional edges, weakening of the tissue, and incisional hernia formation. Two experimental closure techniques were established to investigate laparotomy healing without suturing the incisional edges. METHODS AND MATERIALS: In 24 dogs median laparotomies were closed applying two techniques following the principle of tension banding. Investigations after 3, 9, and 15 months were laparoscopy, tensiometry, light and electron microscopy and measurement of collagen fibril diameters. RESULTS: Incisions healed without incisional hernias with only minimal adhesion formation. At all time points the tensile strength after the bridging technique (BT) did not differ significantly from that in the control group. Mean tensile strength after BT was higher than after the onlay technique (OT) at all time points but did not reach statistical significance. After 3 months the incisions after OT were significantly weaker than the control group. At all time points fibril diameters after OT were significantly smaller than in the control group. After 3 and 9 months the fibril diameters after OT were significantly smaller than after BT. Incisions healed with little scar formation in spite of a chronic inflammatory reaction. This reaction was more pronounced after OT and made access to the fascia difficult after 3 months. Both techniques led to early postoperative seroma formation. CONCLUSIONS: Applying the principle of tension banding, laparotomies healed without suturing the incisional edges. The effect of foreign material on the ultrastructure of regenerating tissue in direct contact to the incisional region was demonstrated by the OT, in which chronic inflammation disturbed the adequate formation of collagen. Further development of both techniques might allow laparotomy closure according to the physiological requirements of wound healing.