Intra-abdominal sepsis impairs colonic reparative collagen synthesis

Inflammatory response after abdominal surgery

Surgical manipulation of the gut elicits an inflammatory cascade within the intestinal muscularis that contributes to postoperative bowel dysmotility. A range of cytokines is sequentially released into the peritoneal fluid following abdominal surgery, their concentrations reflecting the magnitude of surgical trauma. The overproduction of inflammatory mediators might have detrimental effects on organ function and contribute to the enhanced risk of anastomotic leakage in the presence of sepsis. Specific cellular immune functions such as the microbicidal activity of peritoneal phagocytes are depressed after elective surgery, imposing a risk of infectious complications. Laparoscopic surgery decreases the local and systemic production of cytokines and acute-phase reactants, and better preserves peritoneal immunity compared with open surgery. As concluded from animal studies, the gas used for the pneumoperitoneum may possess substantial immunomodulatory activity.

Colonic anastomotic strength and matrix metalloproteinase activity in an experimental model of bacterial peritonitis

BACKGROUND

Clinical studies report conflicting results on the safety of primary intestinal anastomoses in the presence of peritonitis, and comprehensive experimental data are lacking. The present study investigated whether the strength of experimental colonic anastomoses is affected if surgery is performed in the presence of pre-existing bacterial peritonitis.

METHODS

Colonic anastomoses were constructed in Wistar rats 24 h after caecal ligation and puncture or a sham procedure. Anastomotic strength was assessed by measuring breaking strength and bursting pressure during the first 5 days after operation. Anastomotic hydroxyproline levels were measured and matrix metalloproteinase (MMP) activity was analysed by quantitative gelatin zymography.

RESULTS

Anastomotic strength was lowered in the presence of bacterial peritonitis but in a minor and transient way. The breaking strength was lower only immediately after construction of the anastomosis (- 15 per cent, P = 0.011) and the bursting pressure only on the third postoperative day (- 33 per cent, P = 0.038); no anastomotic dehiscence was observed. At 3 days after operation increased levels of MMP activity were observed but anastomotic hydroxyproline content was not affected by bacterial peritonitis.

CONCLUSION

The influence of bacterial peritonitis on the development of anastomotic strength is limited. This experimental finding lends support to recent clinical studies that have demonstrated the feasibility of constructing a primary anastomosis under these conditions.

Repair of full-thickness bowel injury

OBJECTIVE

Colon surgery is more and more often performed in complex situations such as after trauma, under immunosuppression, or in the elderly. Even under optimal conditions, anastomosis fails in certain situations. The objective of this study was to demonstrate the normal phases of bowel healing and to review the local and systemic factors affecting healing with special attention to critical care variables such as major surgery, acute hemorrhage, and infections.

DATA SOURCE

MEDLINE cited and/or published articles.

DESIGN

Review analysis.

RESULTS

Colon healing is a structured cascade of different phases that can be affected by a multitude of local (infection, ischemia) and systemic (diabetes, malnutrition, anemia, hypothermia, trauma) factors. The normal phases of repair, the resulting bursting pressure as an experimental index of healing, and the available published data on local and systemic factors affecting healing are summarized.

CONCLUSION

Several local and systemic factors negatively affect bowel healing; there is still a small portion of patients who fail to heal, suggesting that intrinsic factors need to be analyzed.

Incisional hernias. I. Related risk factors

Incisional hernias represent one of the most frequent complications of abdominal surgery. The incidence is probably underestimated. The pathogenesis is complex and not fully understood, implying patient-related factors (i.e., collagen biochemistry, obesity, age) as well as technical factors, including, among others, wound infection, suture material, and types of incisions and closures. In this paper, the first of two, the authors review the literature emphasizing the current knowledge concerning the pathogenesis of incisional hernias. The second article is focused on the treatment.

Antithrombin III prevents deleterious effects of remote ischemia-reperfusion injury on healing of colonic anastomoses

BACKGROUND

Antithrombin III is known as the most important natural inhibitor of thrombin activity and has been shown to attenuate local harmful effects of ischemia-reperfusion injury in many organs. In recent animal studies, delaying effect of remote organ ischemia-reperfusion injury on healing of intestinal anastomoses has been demonstrated. In this study, we investigated whether antithrombin III reduces deleterious systemic effects of ischemia-reperfusion injury on healing of colonic anastomoses in rats.

METHODS

Anastomosis of the left colon was performed in 24 rats that were divided into three groups: sham operated control (group I, n = 8), 30 minutes of intestinal ischemia-reperfusion by superior mesenteric artery occlusion (group II, n = 8), antithrombin III treated group (250 U/kg before and after the ischemia-reperfusion, group III, n = 8). On postoperative day 6, all animals were sacrificed, and bursting pressure and tissue hydroxyproline content of the anastomoses were assessed and compared.

RESULTS

On postoperative day 6 the mean bursting pressures were 149.6 +/- 4.8, 69.8 +/- 13.5, and 121.8 +/- 8.7 mm Hg for groups I, II, and III, respectively (P = 0.000). Mean tissue hydroxyproline concentration values were 389.5 +/- 29.6, 263.1 +/- 10.0, and 376.0 +/- 33.8 microg/mg for groups I, II, III respectively (P = 0.005).

CONCLUSIONS

This study showed that, antithrombin III treatment significantly prevented the delaying effect of remote organ ischemia-reperfusion injury on anastomotic healing in the colon. Further clinical studies are needed to clarify whether antithrombin may be a useful therapeutic agent to increase the safety of the anastomosis during particular operations where remote organ ischemia-reperfusion injury takes place.

Early postoperative enteral feeding increases anastomotic strength in a peritonitis model

BACKGROUND

Tumor necrosis factor alpha (TNF-alpha) has been shown to decrease collagen synthesis and increase collagenase activity leading to impaired wound healing. Our hypothesis was that immediate postoperative feeding would decrease TNF-alpha, therefore increasing anastomotic healing in a peritonitis model.

METHODS

Twelve Sprague-Dawley rats underwent cecal ligation and puncture to induce peritonitis. Six hours after induction of peritonitis an ileocecectomy and ileocolostomy was performed. Group 1 animals (n = 6) had immediate access to food and water, whereas group 2 (n = 6) had free access to water only. At 48 hours, weight loss, nitrogen loss, anastamotic bursting strength (ABS), TNF-alpha, interleukin-6 (IL-6), and IL-10 were measured.

RESULTS

Weight loss was similar in the two groups. Group 1 rats had a significantly lower mean TNF-alpha level (17.3 +/- 10 versus 17.3 +/- 10 mcg/Dl, P = 0.05). ABS was also significantly higher in group 1 rats when compared with group 2 rats (81 +/- 34 versus 39 +/- 13 mm HG, P = 0.03).

CONCLUSIONS

These data suggest that immediate postoperative feeding results in a beneficial change in the cytokine profile.

Small fragment wounds: biophysics, pathophysiology and principles of management

Military surgical doctrine has traditionally taught that all ballistic wounds should be formally managed by surgical intervention. There is now, however, both experimental and clinical evidence supporting the nonoperative treatment of selected small fragment wounds. Low energy-transfer wounds affecting the soft tissues, without neuro-vascular compromise and with stable fracture patterns, may be suitable for early antibiotic treatment. The management of ballistic wounds to the gastrointestinal tract requires surgical intervention but, advances in the treatment of these wounds, especially those involving the colon, may allow more effective treatment with a reduced morbidity.

Effect of early postoperative feeding on the healing of colonic anastomoses in the presence of intra-abdominal sepsis in rats

PURPOSE

Intra-abdominal infection is generally considered a major risk factor for dehiscence of primary colon anastomosis. To elucidate the indications for nutritional support during intra-abdominal sepsis, we investigated the healing of anastomoses in an animal model.

METHODS

Twenty male Sprague-Dawley rats (280-320 g) underwent cecal ligation and single puncture. After 24 hours the perforated cecum was removed, and the left colon was transected and anastomosed in a single-layer inverted fashion. Animals were randomly assigned to receive both chow and water (early-fed group; n = 10) or water alone for the first 72 hours and chow thereafter (late-fed group; n = 10). Colon-bursting pressure was measured five days after the anastomosis, at which time the anastomosis was excised.

RESULTS

The survival rate after cecal ligation and single puncture was 100 percent, and blood cultures were positive in 20 percent of animals five days after surgery. All data are expressed as means +/- standard error of the mean. Body weight increased more in the early-fed group than in the late-fed group (15.6+/-3 vs. -6.3+/-2.8 g; P < 0.001). Early feeding resulted in increased anastomotic bursting pressure (200+/-11 vs. 161+/-12 mmHg; P < 0.05) and total collagen concentration at the site of anastomosis (2.36+/-0.09 vs. 2.01+/-0.07 microg/mg wet tissue; P < 0.01) compared with the late-fed group.

CONCLUSION

Early feeding has a positive effect on anastomotic healing in the presence of intraabdominal sepsis. The mechanism by which early feeding enhances the colonic anastomotic healing is unclear, although preservation of colonic collagen seems to play a significant role.

Hyaluronic acid-based agents do not affect anastomotic strength in the rat colon, in either the presence or absence of bacterial peritonitis

BACKGROUND

Hyaluronic acid (HA) agents reduce postsurgical adhesion formation. The effect of their perioperative administration on early anastomotic healing is unknown. This study investigated the influence of two HA-containing agents on the development of strength in colonic anastomosis during the first postoperative week, both in normal rats and in rats with bacterial peritonitis.

METHODS

In 90 male Wistar rats a 1-cm segment was resected from the descending colon and an end-to-end anastomosis was constructed. In 108 rats a bacterial peritonitis was induced using caecal ligation and puncture (CLP). Some 24 h after CLP the abdomen was reopened, the caecum was taken out and, after resection of a 1-cm segment, an anastomosis was made. Animals in both groups were randomized to receive either an HA-carboxymethylcellulose (CMC) bioresorbable membrane, 0.4 per cent HA solution or no treatment. One-third of each group was killed at day 1, 3 and 7 after operation. Cultures were taken from the abdominal cavity for microbiological analysis in half of the animals. Subsequently, both bursting pressure and breaking strength were determined as parameters for anastomotic strength.

RESULTS

No differences in anastomotic bursting pressure or breaking strength were found between the experimental groups and their controls. In addition, there was no significant difference in the number of bacteria cultured from the abdominal cavity between rats treated with HA and controls.

CONCLUSION

Neither HA-CMC bioresorbable membrane nor 0.4 per cent HA solution interferes with the development of early anastomotic strength in the colon, and can therefore be safely used to prevent intra-abdominal adhesion formation after performing bowel anastomosis.

Effect of local and remote ischemia-reperfusion injury on healing of colonic anastomoses

BACKGROUND

Although the effect of locally applied ischemia-reperfusion (I-R) injury on gastrointestinal anastomoses has been studied, to our knowledge there is no previous study that investigates the effect of remote I-R injury on gastrointestinal anastomotic healing. The aim of this study was to investigate and compare the effects of local I-R injury and remote I-R injury on the healing of colonic anastomoses.

METHODS

Anastomosis of the right colon was performed in 30 rats that were divided into 5 groups. Group 1 was the control group. In Group 2, I-R was applied to the colonic segment containing the anastomosis. Unilateral lower extremity I-R, unilateral renal I-R, and segmental small intestinal I-R was applied to the rats in Groups 3, 4, and 5, respectively, at the same time as colonic anastomosis. On the fourth postoperative day, animals were killed and bursting pressure and tissue hydroxyproline concentration of the anastomoses were analyzed and compared.

RESULTS

The mean bursting pressure values were: 143 mm Hg in Group 1, 40.8 mm Hg in Group 2, 82.8 mm Hg in Group 3, 46.1 mm Hg in Group 4, and 52.3 mm Hg in Group 5 (P <.0001; 1-way analysis of variance). Mean tissue hydroxyproline concentration values were: 5.3 microg/mg in Group 1, 1.6 microg/mg in Group 2, 2.2 microg/mg in Group 3, 1.3 microg/mg in Group 4, and 1.5 microg/mg in Group 5 (P <. 0001, 1-way analysis of variance). Bursting pressure and tissue hydroxyproline concentration values had a good correlation r = 0.86, P <.001, Pearson correlation analysis).

CONCLUSIONS

This study showed that I-R injury is a systemic phenomenon, and remote organ I-R can significantly delay anastomotic healing. This has to be kept in mind when constructing an intestinal anastomosis in the presence of local or remote I-R injury.

Influência da peritonite sobre a síntese de colágeno em anastomoses do cólon distal: estudo experimental em ratos

Com o objetivo de verificar a relação entre a concentração de colágeno e a capacidade de suportar pressão em anastomoses de cólon quando existe peritonite, utilizaram-se 40 ratos machos, Wistar-TECPAR, com idade média de 120 dias e peso médio de 302 g, os quais foram divididos em 2 lotes de 20 animais que compuseram os grupos controle e peritonite. Sob anestesia inalatória e submetidos à laparotomia os ratos do grupo peritonite tiveram infecção induzida pelo método de Wichterman e col. e os do grupo controle laparotomia com manipulação dos segmentos intestinais envolvidos no experimento. Após 24 horas eram relaparotomizados, sofriam colotomia transversa total esquerda à 2,0 cm da reflexão peritoneal e anastomose em plano único, extra-mucoso. As aferições foram realizadas nop tereciro e sétimo dias de pós-operatório. Ressecava-se 4,0 cm do cólon esquerdo contendo a anastomose e media-se a pressão de ruptura. Realizou-se estudo histopatológico, empregando-se a coloração do Sirius-red e análise da concentração de colágeno através de método computadorizado. Verificou-se que a capacidade de suportar pressão aumentou com o tempo de evolução de forma semelhante nos dois grupos. A concentração de colágeno foi menor no grupo com peritonite no terceiro dia (p = 0,000168) e no sétimo dia (p = 0,0020). Os percentuais de colágeno I e III foram semelhantes no terceiro dia. Já no sétimo dia, no grupo peritonite predominou o colágeno tipo III ( p = 0,000079). Os resultados analisados demonstram que existe diminuição da concentração e da maturação do colágeno nas anastomoses colo-cólicas realizadas quando existe peritonite porém esta alteração não interfere na capacidade da anastomose suportar pressão.

Effect of persistently elevated intraabdominal pressure on healing of colonic anastomoses

BACKGROUND

The adverse effects of elevated intraabdominal pressure (IAP) on abdominal organs are realized, but its influence on anastomotic healing has not been studied. The aim of this study was to evaluate the effect of elevated IAP on healing of colonic anastomoses.

METHODS

Thirty rats, which all had right colonic anastomoses, were divided into five groups. Group 1 was the control group, and group 2 had fecal peritonitis. IAP was maintained between 4 to 6 mm Hg in group 3, 8 to 12 mm Hg in group 4, and 14 to 18 mm Hg in group 5 until all rats were sacrificed on day 4. Bursting pressures and tissue hydroxyproline concentrations of anastomoses were then analyzed and compared.

RESULTS

Mean +/- SEM of bursting pressures were 143+/-2.9 mm Hg in group 1, 72+/-14.4 mm Hg in group 2, 77.3+/-7.9 mm Hg in group 3, 57.5+/-11.2 mm Hg in group 4, and 40.1+/-9.6 mm Hg in group 5 (P<0.0001, one-way analysis of variance [ANOVA]). Mean +/- SEM of tissue hydroxyproline concentrations were 5.3+/-0.3 microg/mg in group 1, 4.7+/-0.5 microg/mg in group 2, 4.6+/-0.6 microg/mg in group 3, 3.6+/-0.5 microg/mg in group 4, and 2.4+/-0.2 microg/mg in group 5 (P = 0.0026, one-way ANOVA). The bursting pressure and hydroxyproline concentrations had good correlation (P<0.001, r = 0.76).

CONCLUSIONS

Elevated IAP delays healing of colonic anastomoses and 4 to 6 mm Hg IAP delays healing as much as fecal peritonitis. More elevated IAP delays healing more than fecal peritonitis. These events may be clinically important and may result from local-systemic effects of IAP.

The Effect of Peritoneal Contamination on Wound Strength of Small Bowel and Colonic Anastomoses

Primary bowel repair in the face of peritoneal soilage is still a controversial area. Previous studies using the rat model have demonstrated a difference in new collagen synthesis after 24 hours of peritoneal contamination. Currently, the effect of short-term fecal contamination of the peritoneal cavity on anastomotic healing and strength is not known. This study was designed to evaluate anastomotic wound strength in the face of fecal contamination during this time period. Twenty Sprague Dawley rats were randomized into two groups: twelve-hour control (n = 10) and 12-hour cecal ligation and puncture (CLP; n = 10). Both groups underwent laparotomy with either CLP (12-hour) or cecal manipulation (12-hour control). Animals were allowed to recover for 12 hours, according to their assigned groups. A second laparotomy was subsequently performed in which the CLP groups had partial cecectomy to remove the source of contamination, followed by mid-jejunal and colonic division with associated primary anastomosis. Control groups had a similar procedure without partial cecectomy. All abdomens were irrigated, and all animals received immediate postoperative antibiotics and an initial fluid bolus. Animals were recovered and received 3 days of postoperative antibiotics. On postoperative day 4, animals were sacrificed and anastomotic sites were resected. Specimens were then placed in a tensiometer and disrupted under dynamic stress. Peak load was recorded for each, and maximum standard load was calculated. Hydroxyproline content of each segment was also determined after disruption. CLP values were compared with control values using unpaired Student's t test. Statistical significance threshold was P < 0.5. There was no significant difference in maximum anastomotic wound strength or hydroxyproline content between 12-hour CLP and 12-hour control group for both small bowel and colon anastomoses. Short-term peritoneal soilage (12-hour) does not significantly effect the maximum tensile strength or hydroxyproline content of primary small bowel or colonic anastomoses in this model. This study suggests that short-term fecal contamination of the peritoneal cavity may not be a contraindication to primary bowel anastomosis.

Influence of 5-fluorouracil on colonic healing and expression of transforming growth factor-beta 1

BACKGROUND

Administration of chemotherapeutic agents in the immediate postoperative period may have beneficial effects by decreasing local cancer recurrence rates, but this must be weighed against possible impairment of wound healing. Since local expression of transforming growth factor-beta1 (TGF-beta1) is normally upreglated following creation of experimental colonic anastomoses, this study examines the effects of 5-fluorouracil (5-FU) on colonic healing and on the local expression of TGF-beta1.

MATERIALS AND METHODS

Forty-eight male Sprague-Dawley rats underwent transection of the descending colon with primary anastomosis and were then randomly assigned to receive either intraperitoneal 5-FU (20 mg/kg/day) or saline (SAL). On Postoperative Days (PODs) 3, 5, and 7, bursting pressure (BP, mm Hg) and bursting energy (BE, mm Hg xs) were determined in situ. Anastomotic and nonoperated segments of colon were harvested and analyzed using the semiquantitative reverse transcriptase-polymerase chain reaction to determine the relative expression of TGF-beta1 normalized to that of a constitutive gene.

RESULTS

Progressive increases in BP and BE were observed in both the 5-FU and the SAL groups, across the time course examined. Overall, these measures were decreased in the 5-FU groups compared to SAL, significantly so on PODs 5 and 7; BP, 127.8 +/- 7.6 vs 161.1 +/- 7.2 and 139.9 +/- 10.9 vs 186.0 +/- 8.6; BE, 1093.6 +/- 190.0 vs 2207.9 +/- 308.2, and 1518.5 +/- 326.5 vs 3279.3 +/- 225.7, respectively. Anastomotic TGF-beta1 expression also increased progressively in both groups over the postoperative time course. Expression in the 5-FU group, however, was significantly decreased compared to that in the SAL group on POD 3; 0.42 +/- 0.05 vs 0.84 +/- 0.04. Interestingly, this preceded the reduction in BP and BE in the 5-FU group on PODs 5 and 7. TGF-beta1 expression in nonoperated colonic segments did not change during the time points studied or in response to 5-FU administration.

CONCLUSIONS

Wound healing following a colonic anastomosis is associated with local increases in TGF-beta1 expression, which in turn is diminished by the administration of 5-FU. If this deleterious effect on wound healing could be counteracted, then chemotherapy administration in the immediate postoperative period may become safer.

Tumor necrosis factor binding protein improves incisional wound healing in sepsis

BACKGROUND

Sepsis is associated with poor wound healing; however, the exact role of tumor necrosis factor (TNF) as a mediator of sepsis-induced alterations in different types of tissue repair is unknown. This study examines the effects of a specific TNF antagonist (TNFbp) on the healing of intestinal anastomoses, incisional wounds, and polyvinyl (PVA) sponge implants in chronic abdominal sepsis.

METHODS

Three groups of male Sprague-Dawley rats were studied: control, sepsis, and sepsis + TNFbp. Jejunal resection and anastomosis were performed through a 4-cm upper midline incision on day 1. On day 3, sepsis was induced by creation of a chronic abdominal abscess. Saline (0.1 ml) or TNFbp (1.0 mg/kg, 0.1 ml) was injected subcutaneously every day starting 4 h prior to sepsis. On day 7, the wound-breaking strength (WBS) of the skin incision and intestinal anastomoses was determined using a tensiometer. Wound histology and collagen deposition were evaluated by comparison of Sirius red-stained sections. The hydroxyproline content of PVA sponges was used to quantitate collagen content under the different experimental conditions.

RESULTS

Septic mortality (20% vs 26%) was not significantly altered by TNFbp. Septic animals demonstrated a reduction in food consumption on days 3 to 5 that was not affected by TNFbp administration. Neither sepsis nor TNFbp altered the breaking strength or histologic appearance of intestinal anastomoses. However, the breaking strength of incisional wounds was decreased by 40% in septic rats (P < 0.001 vs controls). Administration of TNFbp to septic rats significantly improved incisional WBS (P < 0.01 vs sepsis), but not to control levels. Serius red staining of incisional wounds and PVA sponges demonstrated a decrease in collagen organization and deposition in septic rats that was ameliorated by TNFbp. Similarly, the reduction in hydroxyproline content of PVA sponges from septic animals was prevented by TNFbp.

CONCLUSIONS

The process of tissue repair in intestine and skin wounds appears to be significantly different following the septic insult. The healing of jejunal anastomoses was refractory to the catabolic effects of sepsis. In contrast, collagen deposition and organization are significantly decreased in cutaneous wounds during chronic sepsis. TNFbp significantly ameliorated the inhibitory effects of sepsis on cutaneous wound healing. These results suggest that TNF is an important mediator of the decrease in collagen deposition observed in cutaneous wounds during the septic state.

Bacterial products primarily mediate fibroblast inhibition in biomaterial infection

PURPOSE

The stimulation of fibroblast growth is essential for the normal healing and tissue integration of biomaterials. The local elevation of proinflammatory mediators in infected perigraft fluid (PGF) may inhibit this growth. We sought to determine whether infected PGF inhibited fibroblast growth, and, if so, whether this was primarily dependent on the biomaterial, bacteria, or host.

METHODS

In vivo Dacron or expandable polytetra-fluoroethylene (ePTFE) grafts, sterile or colonized with slime-producing (RP-62A, viable or formalin-killed) or nonslime-producing (RP-62NA) Staphylococcus epidermidis (1 x 10(7) CFU/cm2), were implanted in Swiss Webster mice, and the PGF was harvested at 7 and 28 days. Antibodies to tumor necrosis factor alpha, interleukin 1 alpha, interferon gamma (7 micrograms/day), and indomethacin (50 micrograms/day) were administered by microinfusion pumps for 7 days and the PGF was harvested. Inhibition of the proinflammatory mediators was confirmed by enzyme-linked immunosorbant assay. The nontreated, heat-treated, or trypsin-digested in vivo PGF was incubated with an in vitro [3H]thymidine murine fibroblast (ATCC CCL-12) proliferation assay.

RESULTS

Fibroblast inhibition was significant at 7 and 28 days with infected PGF incubation compared with sterile and was not dependent on bacterial slime production or viability. Dacron sterile PGF did not significantly inhibit fibroblasts compared with control, whereas sterile ePTFE stimulated (P < 0.05) fibroblasts. Treatment of the PGF with proinflammatory cytokines, heat, and trypsin failed to reverse fibroblast inhibition in the infected state.

CONCLUSION

Biomaterial infection is associated with fibroblast inhibition that is dependent primarily on bacterial products and not the host or biomaterial. Conservative intervention strategies for graft infection need to address the problem of poor healing as well as bacterial clearance.

Role of matrix metalloproteinases in healing of colonic anastomosis

PURPOSE

The aim of this study was to compare the distribution of the matrix metalloproteinases (MMPs) during anastomotic healing in a normal colon with that in an ischemic colon in a rabbit. This family of enzymes degrades all components of connective tissue and has been implicated as a cause of anastomotic dehiscence.

METHODS

A left-sided anastomosis was formed in the distal colon of one group of rabbits, and in the other group, 9 cm of distal colon was made ischemic before resection and anastomosis 12 hours later. Tissues from the anastomosis and sites around the colon were removed at 12 hours, 1 day, and 3 days after anastomosis and, also, at 7 days in the normal group. Distribution of the MMPs and their inhibitor, tissue inhibitor of metalloproteinases (TIMP), was localized by indirect immunofluorescence.

RESULTS

In rabbits having only an anastomosis, the MMPs and TIMP-1 were, at all times, seen solely in the anastomotic segment and were strictly confined to the immediate vicinity of the suture line. While in rabbits with an ischemic colon before anastomosis, the MMPs initially extended several centimeters proximally and distally from the suture line. By the third day, however, there were only minor differences between the two models.

CONCLUSION

Distribution of the MMPs and TIMP-1 in normal healing is consistent with a role in the remodeling of colonic anastomosis, but when healing of the colon is compromised, these enzymes are more widespread and may contribute to anastomotic dehiscence.

Healing in the gastrointestinal tract

Healing in the GI tract is rapid when free of complications: Unlike cutaneous healing, in which progress can be observed on a daily basis and intervention instituted early if necessary, healing of the intestinal anastomosis is anatomically obscured from inspection, allowing the surgeon only the patient's parameters of general well-being to judge the success of the operation. For the same reason, complications usually require re-operation, with the associated morbidity of a laparotomy and additional general anesthetic. This places a great responsibility on the surgeon to be cognizant of all the preoperative, intraoperative, and postoperative factors relating to anastomotic healing that might compromise the healing process. Bearing these in mind, along with attention to technical detail, should limit complications to an acceptable level. Patients most at risk are (1) those who perioperatively develop physiologic problems that lead to shock, hypoxia, and resultant anastomotic ischemia, (2) those with radiation-induced tissue injury, (3) those with sepsis, and (4) those with preoperative bowel obstruction. Malnourishment, malignancy, diabetes, steroids, and age also influence outcome to varying degrees. Future advancement in the field of GI healing lies in our ability to manipulate the early struggle between collagen synthesis and collagen breakdown. A profound understanding of the molecular and biochemical pathways and the factors that control them will bring us closer to this goal. Clinically, this may be accomplished by the introduction of wound healing enhancers into the anastomotic site, possibly by incorporating them into suture materials, biofragmentable anastomotic rings, or staple materials. Already much is known about the influence of different cytokines and growth factors on collagen regulation, knowledge that will help resolve many of the long-standing problems associated with GI surgery.

Sepsis impairs anastomotic collagen gene expression and synthesis: a possible role for nitric oxide

Although intra-abdominal sepsis is known to impair colon healing by inhibiting anastomotic collagen synthesis, the effect of systemic sepsis on this process is unknown. Endotoxins and cytokines associated with sepsis induce nitric oxide synthesis both systemically and locally within colonic tissue. We hypothesized that systemic sepsis impairs colonic healing and examined a possible correlation with nitric oxide expression. Male Sprague-Dawley rats received intraperitoneal injections of either saline (sham group) or Escherichia coli endotoxin (lipopolysaccharide 1 mg/100 g body weight) at Times -24 and -12 hr (LPS group). All animals underwent laparotomy and left colonic anastomosis at Time 0. At 24 and 96 hr postlaparotomy rats were sacrificed, the anastomoses excised, and [3H]-proline incorporation into protein measured as an index of total new protein synthesis (TNP). Digestion with purified collagenase yielded incorporation into the collagen fraction (CDP). Additional sham and LPS-treated rats were sacrificed at 24, 72, and 120 hr, the anastomoses excised, and nitric oxide synthase activity in the tissue measured by the conversion of [3H]-arginine to [3H]citrulline in an ex vivo culture system. Finally, sham and LPS rats were sacrificed at 120 hr for measurement of colon anastomotic bursting pressure. Systemic sepsis significantly impaired new collagen synthesis in anastomotic tissue at 24 hr compared to control samples (P < 0.02). No difference was noted at 96 hr. TNP synthesis was similar in both groups at 24 or 96 hr. Northern blot analysis confirmed a significant decrease in Type I and Type III collagen mRNA expression at 24 hr in septic rats. Anastomotic bursting pressure was also decreased in the septic group (P < 0.003). Sepsis elevated nitric oxide synthase activity in anastomotic tissue 24 hr postanastomosis, when compared to sham tissue (P < 0.0001). These data suggest that systemic endotoxin induces nitric oxide synthesis at the anastomotic site. The simultaneous dysregulation of collagen gene expression and synthesis with decreased anastomotic strength suggests a possible regulatory role for nitric oxide in gastrointestinal healing.