A new anastomotic leakage model in circular double stapled colorectal anastomosis after low anterior rectum resection in pigs

Post-Operative Monitoring of Intestinal Tissue Oxygenation Using an Implantable Microfabricated Oxygen Sensor

Anastomotic leakage (AL) is a common and dangerous post-operative complication following intestinal resection, causing substantial morbidity and mortality. Ischaemia in the tissue surrounding the anastomosis is a major risk-factor for AL development. Continuous tissue oxygenation monitoring during the post-operative recovery period would provide early and accurate early identification of AL risk. We describe the construction and testing of a miniature implantable electrochemical oxygen sensor that addresses this need. It consisted of an array of platinum microelectrodes, microfabricated on a silicon substrate, with a poly(2-hydroxyethyl methacrylate) hydrogel membrane to protect the sensor surface. The sensor was encapsulated in a biocompatible package with a wired connection to external instrumentation. It gave a sensitive and highly linear response to variations in oxygen partial pressure in vitro, although over time its sensitivity was partially decreased by protein biofouling. Using a pre-clinical in vivo pig model, acute intestinal ischaemia was robustly and accurately detected by the sensor. Graded changes in tissue oxygenation were also measurable, with relative differences detected more accurately than absolute differences. Finally, we demonstrated its suitability for continuous monitoring of tissue oxygenation at a colorectal anastomosis over a period of at least 45 h. This study provides evidence to support the development and use of implantable electrochemical oxygen sensors for post-operative monitoring of anastomosis oxygenation.

Is Circular Fibrin Sealing of Low Rectal Anastomosis Able to Prevent Leakage in 21-Day Follow-up? Randomized Experimental Trial in Pigs

Purpose. Clinically apparent anastomotic leakage (AL) after low anterior rectal resection (LAR; <7 cm from anal verge) using circular double-stapled anastomosis without defunctioning stoma is up to 37.5%. However, it is unclear whether there is reduction of LAR after 21 postoperative days without defunctioning stoma but with extraluminal anastomotic application of fibrin sealant. Methods. Forty-eight-week-old pigs underwent LAR and circular double-stapled anastomosis in end-to-end technique (descendo-rectostomy). Animals were randomized into therapy and control group (cg). Therapy group (n = 20) received additional extraluminal circular anastomotic application of fibrin sealant. Objective was to assess incidence of clinically apparent and nonclinically apparent leakage through the 21st postoperative day. Remaining animals were sacrificed on the 21st day, and anastomotic region was analyzed. In case of earlier diagnosed AL, animals were sacrificed. Results. In cg, we observed clinically and nonclinically AL in 20% (n = 4). No animal was identified with a nonclinical-apparent leakage in this group, and all 4 animals with leakages presented clinical signs. In the therapy group, no animal (0/20) developed clinically apparent leakage signs. There were no leakages in this group, but 3 animals had ulcerative lesions without leak and without clinical signs. These lesions were observed intraluminally at crossing of staple lines after 21 days. In one of these animals, incomplete leakage was observed, blocked by fibrin sealant. Conclusion. In circular stapled colorectal anastomosis, circular fibrin glue sealant successfully protected anastomotic intraluminal wall defects at crossing of staple lines, reducing leakage rate from 20% to 0% (cg vs therapy group) after 21 postoperative days.

In vivo validation of a miniaturized electrochemical oxygen sensor for measuring intestinal oxygen tension

Recent advances in the fields of electronics and microfabrication techniques have led to the development of implantable medical devices for use within the field of precision medicine. Monitoring visceral surface tissue O₂ tension (PTo2) by means of an implantable sensor is potentially useful in many clinical situations, including the perioperative management of patients undergoing intestinal resection and anastomosis. This concept could provide a means by which treatment could be tailored to individual patients. This study describes the in vivo validation of a novel, miniaturized electrochemical O₂ sensor to provide real-time data on intestinal PTo2. A single O₂ sensor was placed onto the serosal surface of the small intestine of anesthetized rats that were exposed to ischemic (superior mesenteric artery occlusion) and hypoxemic (alterations in inspired fractional O₂ concentrations) insults. Control experiments demonstrated that the sensors can function and remain stable in an in vivo environment. Intestinal PTo2 decreased following superior mesenteric artery occlusion and with reductions in inspired O₂ concentrations. These results were reversible after reinstating blood flow or by increasing inspired O₂ concentrations. We have successfully developed an anesthetized rat intestinal ischemic and hypoxic model for validation of a miniaturized O₂ sensor to provide real-time measurement of intestinal PTo2. Our results support further validation of the sensors in physiological conditions using a large animal model to provide evidence of their use in clinical applications where monitoring visceral surface tissue O₂ tension is important.NEW & NOTEWORTHY This is the first report of real-time continuous measurements of intestinal oxygen tension made using a microfabricated O₂ sensor. Using a developed rodent model, we have validated this sensor's ability to accurately measure dynamic and reversible changes in intestinal oxygenation that occur through ischemic and hypoxemic insults. Continuous monitoring of local intestinal oxygenation could have value in the postoperative monitoring of patients having undergone intestinal surgery.

Efficacy of Human Fibrinogen-Thrombin Patch (TachoSil) Clinical Application in Upper Gastrointestinal Cancer Surgery

BACKGROUND

Previous studies investigated the efficacy and applicability of tissue adhesives in gastrointestinal surgery while no evidence is available to date about a novel compound, TachoSil (Takeda, Zurich, Switzerland). The primary aim of this observational study was to assess the effect of new fibrin sealant on the incidence of postoperative complications in a homogeneous group of patients submitted to upper gastrointestinal surgery for cancer.

METHODS

Two cohorts of 28 and 34 patients undergoing upper gastrointestinal for surgery were compared. In the first cohort, the anastomotic site was treated with TachoSil fibrinogen-thrombin-collagen patches and in the second no collagen sponge or any other hemostatic sealant was used. Postoperative complications and outcomes as well as postoperative biochemical parameters were analyzed.

RESULTS

Postoperative complications occurred in 12 patients (35.3%) and 2 patients (7.1%) in control and collagen sponge group respectively (χ² = 3.539, p < 0.05), with no anastomotic leakage in the collagen sponge group. A binary logistic regression analysis showed that the nonuse of collagen sponge [odds ratio (OR) = 0.025, 95% confidence interval (CI) = 0.001-0.457, p = 0.01] was independently associated with postoperative complication occurrence.

CONCLUSIONS

The addition of fibrinogen-thrombin-collagen sponge patch may reduce postoperative complication rate after upper gastrointestinal surgery for cancer. Further study to delineate the role of TachoSil in gastrointestinal surgery are also needed to demonstrate improved effectiveness and applicability.

International consensus statement regarding the use of animal models for research on anastomoses in the lower gastrointestinal tract

PURPOSE

This project aimed to reach consensus on the most appropriate animal models and outcome measures in research on anastomoses in the lower gastrointestinal tract (GIT). The physiology of anastomotic healing remains an important research topic in gastrointestinal surgery. Recent results from experimental studies are limited with regard to comparability and clinical translation.

METHODS

PubMed and EMBASE were searched for experimental studies investigating anastomotic healing in the lower GIT published between January 1, 2000 and December 31, 2014 to assess currently used models. All corresponding authors were invited for a Delphi-based analysis that consisted of two online survey rounds followed by a final online recommendation survey to reach consensus on the discussed topics.

RESULTS

Two hundred seventy-seven original articles were retrieved and 167 articles were included in the systematic review. Mice, rats, rabbits, pigs, and dogs are currently being used as animal models, with a large variety in surgical techniques and outcome measures. Forty-four corresponding authors participated in the Delphi analysis. In the first two rounds, 39/44 and 35/39 participants completed the survey. In the final meeting, 35 experts reached consensus on 76/122 items in six categories. Mouse, rat, and pig are considered appropriate animal models; rabbit and dog should be abandoned in research regarding bowel anastomoses. ARRIVE guidelines should be followed more strictly.

CONCLUSIONS

Consensus was reached on several recommendations for the use of animal models and outcome measurements in research on anastomoses of the lower GIT. Future research should take these suggestions into account to facilitate comparison and clinical translation of results.

Circular anastomotic experimental fibrin sealant protection in deep colorectal anastomosis in pigs in a randomized 9-day survival study

PURPOSE

The reported rate of clinically apparent anastomotic leakage (AL) in a low anterior resection of the rectum (LAR) (≤7 cm from the anal verge) using a circular double-stapled anastomosis (CDSA) without defunctioning stoma is up to 37.5 %. Since AL may result in life-threatening peritonitis, sepsis, and multiple organ failure, LAR and CDSA are regularly combined with defunctioning stoma. Accordingly, we now evaluated whether LAR and CDSA without defunctioning stoma but with extraluminal anastomotic application of an experimental fibrin sealant reduce the AL rate. This might prevent humans from defunctioning stoma increasing quality of life and decreasing surgical costs.

METHODS

Forty 8-week-old pigs underwent LAR and CDSA in an end-to-end technique (descendo-rectostomy). Animals were randomized into a therapy and control group (gr.). The therapy gr. (n = 20) received an additional extraluminal circular application of an experimental fibrin sealant to the anastomosis. The objective was to assess the incidence of clinically apparent and non-clinically apparent leakage through the ninth postoperative day. Double-contrast barium CT radiographs of the colorectal region were performed on the ninth postoperative day or earlier, in case there were clinical signs of AL. All remaining animals were sacrificed on the ninth postoperative day and the anastomotic region was histopathologically analyzed. In case of earlier diagnosed AL, animals were sacrificed immediately. Blood samples were taken for complete blood count, chemistry, and coagulation profile prior to surgery and on the first, third, fifth, seventh, and ninth postoperative day.

RESULTS

A circular extraluminal anastomotic application of an experimental fibrin protection decreased the rate of clinically and non-clinically apparent AL from 20 % (n = 4) in the control group to 5 % (n = 1) in the treatment group. Ulcerations were also observed in both gr. (control gr.-5 animals, therapy gr. -3 animals). All animals with AL showed necrosis surrounding the hole at the anastomoses. Three additional animals had a full wall defect at the anastomotic region that was blocked by the experimental fibrin sealant. The fibrin sealant was present at necropsy in all treated animals.

CONCLUSION

Circular anastomotic protection with the experimental fibrin sealant blocked anastomotic full wall defects, preventing peritonitis and significantly reducing the AL rate from 25 to 5 %.