Sterile Laparotomy Research Articles

Efficacy of laparotomy sponges to reduce bacterial contamination using an in vitro gastrointestinal surgery model.

Use of laparotomy sponges to protect abdominal viscera during gastrointestinal surgery is described in nonspecific terms by various sources, but no definitive guidelines have been established in veterinary literature. The objective of this study was to compare the in vitro efficacy of various layer-densities of laparotomy sponges at reducing bacterial contamination from multiple contaminant volumes during multiple exposure times. A standardized Escherichia coli inoculum water solution was applied over sterile laparotomy sponges overlying blood agar plates. Four laparotomy sponge layer-densities, 4 volumes of E. coli inoculum water solution, and 4 exposure times were evaluated. All blood agar plates were incubated for 48 hours followed by surface area measurements of colonization of each blood agar plate at 24 and 48 hours. The procedure was repeated thrice. Bacterial colonization occurred on 100% (192/192) of inoculated blood agar plates. There was a statistically significant decrease in colonized area with increasing layer-density of laparotomy sponges (P<0.0001). Comparison between the layer-density of sponges were statistically significant in resulting infected area (P<0.01), except comparison between 6- and 8-layers (P = 0.9490). Colonized area was not significantly altered by time of exposure. Results suggested that increasing the layer-density of laparotomy sponges has significant effect on reducing strikethrough bacterial colonization in an in vitro model. The results of this study can be used when performing gastrointestinal surgery to help guide laparotomy sponge use to reduce peritoneal bacterial contamination.

Time-related changes in hepatic and colonic mitochondrial oxygen consumption after abdominal infection in rats

BackgroundEvidence suggests that early adaptive responses of hepatic mitochondria occur in experimentally induced sepsis. Little is known about both colonic mitochondrial function during abdominal infection and long-term changes in mitochondrial function under inflammatory conditions. We hypothesize that hepatic and colonic mitochondrial oxygen consumption changes time-dependently after sterile laparotomy and in the course of abdominal infection. The aim of the present study was to investigate the hepatic and colonic mitochondrial respiration after sterile laparotomy and abdominal infection over up to 96 h.MethodsAfter approval of the local Animal Care and Use Committee, 95 Wistar rats were randomized into 8 groups (n = 11–12): 1–4 sham (laparotomy only) and 5–8 colon ascendens stent peritonitis (CASP). Healthy, unoperated animals served as controls (n = 9). The mitochondrial respiration in colon and liver homogenates was assessed 24, 48, 72, and 96 h after surgery. Mitochondrial oxygen consumption was determined using a Clark-type electrode. State 2 (oxygen consumption in the presence of the substrates for complexes I and II) and state 3 respiration (ADP dependent) were assessed. The respiratory control ratio (RCR state 3/state 2) and ADP/O ratio (ADP added/oxygen consumed) were calculated for both complexes. Data are presented as means ± SD, two-way ANOVA followed by Tukey’s post hoc test.ResultsHepatic RCR was initially (after 24 h) elevated in both operated groups; after 48 h only, the septic group was elevated compared to controls. In CASP groups, the hepatic ADP/O ratio for complex I was elevated after 24 h (vs. controls) and after 48 h (vs. sham) but declined after 72 h (vs. controls). The ADP/O ratio for complex II stayed unchanged over the time period until 96 h.The colonic RCR and ADP/O did not change over time after sham or CASP operation.ConclusionHepatic, but not colonic, mitochondrial respiration is increased in the initial phase (until 48 h) and normalizes in the longer course of time (until 96 h) of abdominal infection.

The effect of a chitosan coating on the adhesive potential and tensile strength of polypropylene meshes

The polypropylene mesh used for the repair of abdominal wall hernia can cause intraabdominal adhesions. In this study, the effect of chitosan coating of the polypropylene meshes on the adhesion and tensile strength of the meshes was investigated. After coating polypropylene meshes with 2% chitosan, 5×3 cm patches were prepared. Under general anesthesia, sterile laparotomy was performed in 96 Wistar albino female rats that were equally allocated to 6 groups. In the first group, only laparotomy was performed. In the second group, chitosan was applied to the peritoneal cavity, and the laparotomy was closed. In the third group, polypropylene (prolene) patches were used to close the abdomen; in the fourth group, polypropylene polyglecaprone 25 (ultrapro) mesh patches were used to close the abdomen. In the fifth and sixth groups, chitosan-coated versions of the meshes used in the third and fourth groups, respectively, were applied. All skin incisions were closed in all groups. On the 7th and 21stdays, eight randomly selected rats from each group were killed. The abdomen was opened, and the adhesions were evaluated using the diamond score. The tensile strength of the meshes was measured by an Instron 4301 device. The histopathological evaluation of the inflammatory response was performed according to the Ehrlich and Hunt classification. The adhesion score was comparable among mesh groups but higher when mesh groups were compared with the control and chitosan groups (p<0.001). The tensile strength of meshes did not differ among mesh groups. Histopathologically, meshes with or without chitosan were similar in terms of inflammatory findings. The chitosan coating did not affect the adhesion potential, the tensile strength, or the inflammatory response of the polypropylene meshes.

Long-term randomized controlled trial of a novel nanopowder hemostatic agent (TC-325) for control of severe arterial upper gastrointestinal bleeding in a porcine model

Endoscopic therapy of brisk upper gastrointestinal bleeding remains challenging. A proprietary nanopowder (TC-325) has been proven to be effective in high pressure bleeding from external wounds. The efficacy and safety of TC-325 were assessed in a survival gastrointestinal bleeding animal model. 10 animals were randomized to treatment or sham. All animals received intravenous antibiotics, H2-blockers and heparin (activated clotting time 2 × normal). In a sterile laparotomy the gastroepiploic vessels were dissected, inserted through a 1-cm gastrotomy, and freely exposed in the gastric lumen, and the exposed vessel lacerated by needle knife. The treatment group received TC-325 by a modified delivery catheter while the sham group received no endoscopic treatment. Time to hemostasis, and mortality at 60 minutes, 24 hours, 48 hours, and 7 days were noted. Necropsy was performed in all animals. Spurting arterial bleeding was achieved in all animals. No control animal showed hemostasis within the first hour compared with 100 % (5 / 5) in the treatment arm (mean 13.8 minutes, P < 0.0079). Durable hemostasis was achieved with no evidence of rebleeding after 1 and 24 hours in 80 % (4 / 5) of the treated animals compared with none in the control group ( P < 0.0098). None of the control animals survived more than 6 hours. Necropsy at 1 week in treated animals revealed healed gastrotomy without foreign body granuloma or embolization to the lung or brain. TC-325 is safe and highly effective in achieving hemostasis in an anticoagulated severe arterial gastrointestinal bleeding animal model.

A Long-Term Randomized Controlled Trial of a Novel Nanopowder Hemostatic Agent for Control of Severe Upper Gastrointestinal Bleeding in a Porcine Model

Endoscopic therapy of brisk upper GI bleeding remains challenging with the use of conventional endoscopic devices. A proprietary granular mineral blend (TC-325) for the management of high pressure arterial wounds has been proven to be effective for external wounds by the US Army in both Iraq and Afghanistan. Aim: To assess the efficacy and safety of a novel hemostatic nanomaterial in short and long term hemostasis in a survival GI bleeding animal model. Methods: 10 animals randomized into treatment and control group based on a sample size calculation from a pilot study. All animals underwent a sterile laparotomy with dissection of the gastroepiploic vessels. A 1cm gastrotomy was made through which the blood vessels were pushed into the gastric lumen. A gastric incision was then approximated in a standard manner along with the abdominal wall. All animals then received IV antibiotics and daily H2 blocker therapy. To create anticoagulation and worst case scenario, a bolus of heparin (mean of 150units/kg) was given with a target of achieving activated clotting time (ACT) levels 2X the ULN. Double channel endoscope was inserted into the gastric lumen and needle knife injury of the exposed blood vessels. A visual scale of bleeding was used: Grade1 oozing of blood, Grade 2 dripping of blood and Grade 3 pulsatile bleeding from site of injury. The treatment group received endoscopic guided application of nanopowder. A modified delivery catheter was used to deliver the active material. Times to hemostasis, mortality at 60 minutes, 24 hours, 48 hours and 7 days were noted. Necropsy was performed in all animals. Results: Creation of the active GI bleeding model by laparotomy with gastroepiploic vessel exposure was successful. A grade 3 injury and bleeding was achieved in all animals. None of the control group animals achieved hemostasis within the first hour compared to 100% in the treatment arm (mean 13.8 minutes, P<0.0079). Durable hemostasis was achieved with no evidence of rebleeding after 1 and 24 hours in 80% of the animals in the treatment group as compared to none in the control group (P<0.0098). Endoscopy at day seven revealed no evidence of active bleeding in all animals in the treatment group. None of the animals in the control could survive more than 6 hours because of ongoing bleeding. Necropsy revealed healed gastrotomy with no foreign body granuloma. Lung and brain assessment revealed no evidence of embolization in treatment animals. Conclusion: The endoscopic application of this novel granular mineral nanopowder is safe and highly effective in achieving hemostasis in anticoagulated severe GI bleeding animal model.

Infectious implications in the porcine model of natural orifice transluminal endoscopic surgery (NOTES) with PEG-tube closure: a quantitative bacteriologic study

Obtaining reliable closure of transvisceral defects currently limits natural orifice transluminal endoscopic surgery (NOTES). PEG tubes are potential means of managing NOTES gastrotomies. To determine the efficacy of PEG closure after NOTES. An experimental animal study. A laboratory. The pigs received gastric lavage with saline solution, chloramphenicol, or no lavage, and then underwent transgastric NOTES peritoneoscopy. Cultures were obtained by endoscopy during the surgery. A sterile foreign body was left in the peritoneal cavity. The gastrotomy was closed with a 20F PEG tube. The animals were observed for 14 days and underwent sterile laparotomy. Cultures of the foreign body and the peritoneal cavity were obtained. Abscess rate, peritoneal quantitative cultures. After 1 exclusion for anesthetic complications, 19 animals underwent NOTES; 18 (94.7%) survived the entire postoperative period. One animal died on postoperative day 2 after the PEG tube dislodged. At 14 days, 5 animals (27.8%) had intra-abdominal abscesses, 8 (44.4%) had positive peritoneal cultures, and 9 (50%) foreign bodies were contaminated on culture. Infectious complications were not altered by the type of gastric lavage or peritoneal bacterial inoculum introduced at the time of surgery. An animal model. PEG closure of a NOTES gastrotomy is associated with subclinical intra-abdominal abscess formation and can result in death when the tube is dislodged during the early postoperative period. Preprocedural gastric lavage does not alter the intra-abdominal bacterial burden introduced at the time of surgery or subsequent infectious outcomes in the porcine model. These concerning findings necessitate additional studies to determine if porcine models are appropriate and applicable to human subjects in the NOTES setting.

Effect of Laparotomy on Clearance and Cytokine Induction inStaphylococcus aureus–infected Lungs

Staphylococcus aureus is a major pathogen complicating postsurgical care. To test the effect of sterile laparotomy (LAP) on pulmonary clearance of S. aureus in a murine model. Control and LAP mice were infected intranasally with 10(8) cfu of S. aureus. Microbial clearance, pulmonary leukocyte recruitment, and cytokine profiles were compared between the groups. Antibody neutralization or cytokine gene knockout mice were used to evaluate the role of cytokines. Laparotomy resulted in a 10-fold increase in S. aureus lung colony-forming units on Days 2 and 3 postinfection. Both groups cleared the infection by Day 4. No defect in leukocyte recruitment into the lungs was observed in infected LAP animals; however, an increase in the number of Mac-3-positive cells and a significant decrease of cells with high surface expression of Fc-gammaR suggest suboptimal activation of leukocytes in the lungs of infected LAP animals. Infected LAP mice had decreased expression of interferon (IFN)-gamma and increased expression of mRNA for IL-13 in the lungs on Day 1 postinfection and decreased levels of IL-6, keratinocyte-derived chemokine (KC), and macrophage inflammatory protein-2 (MIP-2) in bronchoalveolar lavage at Day 2 postinfection. Neutralization of IFN-gamma mimicked the effect of LAP with impaired clearance on Day 2. Sterile LAP induced temporary deactivation of innate immune responses to pulmonary S. aureus challenge. Impaired microbial clearance was accompanied by altered cytokine expression and suboptimal activation of pulmonary leukocytes. Lack of early IFN-gamma induction in the infected lungs of LAP animals is a likely mechanism contributing to the observed phenotype.

Computer-assisted electrocoagulation: Bipolar vs. monopolar in the treatment of experimental canine gastric ulcer bleeding

A prospective, randomized, controlled experiment using a canine model of severely bleeding gastric ulcer was performed to compare the hemostatic efficacy and tissue damage produced by one bipolar and two monopolar electrodes. Both monopolar electrodes were insulated to their tips; they differed with respect to their surface area (3 mm2 vs. 4 mm2). The force of electrode application was controlled. An analog computer monitored the energy per electrode application and predetermined the duration of each application. Fifty-nine standard acute bleeding ulcers were made and treated one at a time in six heparinized foxhounds at sterile laparotomy. Treatment was randomized to the bipolar or to one of the monopolar electrodes within each of three bleeding strata. No significant difference was observed in hemostatic efficacy among the three electrodes. Treated ulcers were examined histologically after 5 to 7 days to determine the maximum tissue damage produced: Bipolar electrocoagulation caused significantly less damage than electrocoagulation with either monopolar electrode. We conclude that with these electrodes, bipolar electrocoagulation is equally effective for stopping bleeding but results in less tissue injury than monopolar electrocoagulation in this experimental model.

Argon vs. neodymium YAG laser photocoagulation of experimental canine gastric ulcers

A neodymium YAG (Nd: YAG) laser was evaluated in a dog ulcer model used in the same manner as is recommended for bleeding patients (power 55 W, divergence angle 4 °, with CO2 gas-jet assistance). The experiments were performed during sterile laparotomy in heparinized dogs. Bleeding gastric ulcers were photocoaguiated until bleeding stopped and then examined histologically 7 days later when depth of tissue injury was maximal. In the first series of experiments, the Nd:YAG laser was compared with the 7-W argon laser in the same dogs. Both lasers stopped bleeding from all experimental ulcers. The 55-W Nd:YAG laser caused full-thickness injury to the gastric wall beneath 11 of the 14 treated ulcers, whereas the 7-W argon laser caused no full-thickness injury beneath 14 treated ulcers. In a second series of experiments, we tried to determine whether varying exposure times with the 55-W Nd:YAG laser would make it less injurious; it did not. In a third series of experiments, the 55-W Nd: YAG laser was tested with and without CO2 gasjet assistance in order to determine if this would affect the depth of injury; it did not. In the final series of experiments, the wattage of the Nd:YAG laser was varied to see if this would reduce depth of injury; lower wattage did not stop bleeding, and intermediate and higher wattages did stop bleeding but did not reduce depth of injury. We conclude that the 55-W Nd: YAG laser as it is currently used clinically produces deeper tissue damage than the argon laser in our animal model. This damage is not reduced by changes in power, duration of exposure, or the presence of gas-jet assistance.

Endoscopic laser treatment: III. Development and testing of a gas-jet-assisted argon laser waveguide in control of bleeding experimental ulcers

The purpose of this study is to evaluate the efficacy and safety of a new argon laser system for stopping bleeding from experimental canine gastric ulcers. This system consists of a catheter which can be inserted via an endoscopic biopsy channel to deliver a jet of CO2 coaxially with an argon laser beam. The efficacy of this system in stopping bleeding was tested in two acute experiments at laparotomy in heparinized dogs using our gastric ulcer model. At 7 w of power the gas-jet-assisted laser proved 100% effective in stopping bleeding with an average of three 5-sec exposures, as compared to the same laser without added CO2, which required an average of 11 5-sec exposures. Furthermore, the 7-w laser without added CO2 did not stop all bleeding ulcers. The safety of the CO2 laser system was tested in a chronic experiment at sterile laparotomy using the same ulcer model. No ulcer treated with the 7-w gas-jet-assisted argon laser showed histologic evidence of full thickness injury. A final acute experiment compared the efficacy of various wattages of the gas-jet-assisted laser in stopping bleeding from the ulcer model; the wattages used in this series of experiments and in previous experiments proved to be in the efficacious range. We conclude that CO2 added coaxially to a 6- to 7-w argon laser increases the efficacy of coagulation while reducing the depth of injury.

The heater probe: A new endoscopic method for stopping massive gastrointestinal bleeding

We have developed a heater probe which can be passed via an endoscope and which can apply pressure and heat simultaneously to a bleeding vessel. A 6.4-mm diameter prototype and a 3.2-mm diameter working model of this device have been tested for efficacy in stopping massive bleeding in experimental canine gastric ulcers. Randomized, internally controlled experiments were carried out at laparotomy in heparinized dogs using standard-sized gastric ulcers made and treated via an ample gastrotomy. In acute experiments the heater probe stopped bleeding from all treated ulcers, whereas all untreated control ulcers continued bleeding. In chronic studies performed at sterile laparotomy the depth of injury produced by heater probe coagulation was systematically evaluated; dogs were killed at intervals from 1 week to 1 month. No perforations occurred, but histological injury was evident extending from the ulcer base to the serosa in 7 of the 18 ulcers treated with the 6.4-mm probe and in 2 of the 30 ulcers treated with the 3.2-mm probe. In a preliminary endoscopic experiment the 3.2-mm probe stopped bleeding in 18 of 19 acute experimental ulcers. Histological evidence of injury extending to the serosa occurred in six instances; no perforations occurred. The efficacy in stopping bleeding with this method is satisfactory, but the depth of injury should be reduced before considering application to human beings.