Abstract

Background: Staple-line leak is the most frightening complication of laparoscopic sleeve gastrectomy and several predisposing factors such as using improper staple sizes regardless of gastric wall thickness, narrower bougie diameter and ischemia of the staple line are asserted.
Aims: To evaluate the effects of different bougie diameters on tissue oxygen partial pressure at the esophagogastric junction after sleeve gastrectomy.
Study Design: A randomized and controlled animal experiment with 1:1:1:1 allocation ratio.
Methods: Thirty-two male Wistar Albino rats were randomly divided into 4 groups of 8 each. While 12-Fr bougies were used in groups 1 and 3, 8-Fr bougies were used in groups 2 and 4. Fibrin sealant application was also carried out around the gastrectomy line after sleeve gastrectomy in groups 3 and 4. Burst pressure of gastrectomy line, tissue oxygen partial pressure and hydroxyproline levels at the esophagogastric junction were measured and compared among groups.
Results: Mortality was detected in 2 out of 32 rats (6.25%) and one of them was in group 2 and the cause of this mortality was gastric leak. Gastric leak was detected in 2 out of 32 rats (6.25%). There was no significant difference in terms of burst pressures, tissue oxygen partial pressure and tissue hydroxyproline levels among the 4 groups.
Conclusion: The use of narrower bougie along with fibrin sealant has not had a negative effect on tissue perfusion and wound healing.

Obesity is a pandemic condition and a major health problem in both developed and developing countries. According to the World Health Organization data, 39% and 13% of adults aged 18 years and over are overweight and obese, respectively (1). Laparoscopic sleeve gastrectomy (LSG) is one of the most popular techniques used for weight loss in several countries, including the USA (2). LSG was initially advocated as the first step of a two-staged procedure for high-risk super-obese patients (3). In recent years, LSG has become a popular procedure, and its resulting weight loss and comorbidity resolution are similar to those of laparoscopic gastric bypass (4-6). Staple line leak is one of the most frequent and serious complications of LSG. Gastric leak rates are reported to be around 0%-20% in different studies (7,8), and the location of the leak in the vast majority of cases (92%) is the proximal region of the esophagogastric junction (EGJ) (7). However, the risk of staple line leak is of great concern and needs further investigation. In literature, several predisposing factors of staple line leak include using improper staple sizes regardless of gastric wall thickness, narrow bougie diameter, and ischemia of the staple line (7,9). Thus far, no quantitative study has been conducted on the relationship between staple line leak and tissue ischemia. Hence, this study aims to evaluate the effects of different bougie diameters on tissue oxygen partial pressure (PtO₂) at the EGJ after sleeve gastrectomy.

MATERIALS AND METHODS

Animals, experimental protocol, and study design

Thirty-two male Wistar albino rats, with an average weight of 317±9.4 g and aged 8 months, were used in this study. The animals were randomly divided into four groups, with eight rats each. Group 1 underwent sleeve gastrectomy via 12-Fr bougie; group 2 underwent sleeve gastrectomy via 8-Fr bougie; group 3 underwent sleeve gastrectomy via 12-Fr bougie followed by fibrin sealant (Tisseel^® fibrin sealant; Baxter, Deerfield, Illinois, USA) application around the gastrectomy line; and group 4 underwent sleeve gastrectomy via 8-Fr bougie followed by fibrin sealant application around the gastrectomy line. The study was designed as a randomized and controlled animal trial with 1:1:1:1 allocation ratio and performed in the Animal Laboratory of Ankara University School of Medicine in Ankara, Turkey. The computer-generated random sequences of numbers were used for randomization.

Ethics statement

The study was approved by the Animal Experiments Ethics Committee in Ankara University (Approval number: 13-11-79) in concordance with the Guide for the Care and Use of Laboratory Animals published by the US National Institutes of Health.

Surgical technique

The operations were performed under heat lamps to maintain the body temperature within 35 °C-36 °C and by the same surgeon conductive keratoplasty with the same technique. Anesthesia was attained by intramuscular injection of 40 mg/kg body weight ketamine (Ketalar^®; Parke-Davis, Eczacıbaşı, İstanbul, Turkey) and 5 mg/kg body weight xylazine (Rompun^®; Bayer Türk, İstanbul, Turkey). The subjects respired spontaneously during the operation, and 12-hour day/12-hour night cycles were provided. Laparotomy was performed with a 3 cm midline incision following cleaning with 10% povidone–iodine. After dissection of the greater curvature by using 4/0 silk sutures (Sterisilk^®; SSM, İstanbul, Turkey), gastrotomy was performed 5 mm proximal to the pylori, and the gastric contents were aspirated. An aspiration catheter (as a bougie) was placed aside for lesser curvature through the gastrotomy. With the guidance of the bougie, a bulldog clamp was placed on the stomach longitudinally, and sleeve gastrectomy was performed over the clamp. The gastrectomy line was closed with double-layer continuous technique using 6/0 Prolene^® sutures (Ethicon US, Cleveland, Ohio, USA). The gastrotomy aperture was sutured similarly after the removal of the bougie, and the abdominal fascia and skin were closed with continuous 3/0 silk sutures (Sterisilk^®; SSM, İstanbul, Turkey). The aspiration catheters were used as bougies. Catheters with 12-Fr diameter (Bıçakçılar, İstanbul, Turkey) were used in groups 1 and 3, and those with 8-Fr diameter (Kaishou, Changzhou, Jiangsu, China) were used in groups 2 and 4. Fibrin sealant was applied around the gastrectomy line of subjects in groups 3 and 4.

Postoperative care

Hydration of all subjects was sustained by injecting 3 mL of 0.9% NaCl and 3 mL of 5% dextrose subcutaneously right after the surgery and every 12 hours until postoperative second day. Two milligrams of meloxicam per kilogram was also administered for analgesia. All subjects were monitored under heat lamps until they recovered from anesthesia. All subjects were also observed without oral intake on the day of surgery. On the 1^st and 2^nd postoperative days, water and Ensure Plus^® Vanilla (Abbott, Illınois, USA) were administered ad libitum. Standard rat diet was given to all subjects on the 3^rd postoperative day.

Measurements

The Licox^® monitoring system (Integra Life Sciences Corp., San Diego, California, USA) and 0.6 mm Clark type polarographic microprobes (Licox^® CMP cc1, Integra Life Sciences Corp., San Diego, California, USA) were used to determine tissue PtO₂. His angle of the stomach was identified without impairing its vascular supply. The first PtO₂ measurement (PtO₂-0) was carried out immediately after laparotomy. PtO₂ was measured (PtO₂-1) again in the remnant of the angle of his right after suturing of the gastrectomy line in groups 1 and 2 and right after applying the fibrin sealant in groups 3 and 4. The second laparotomy was performed in all groups on the 30^th day. The stomach was dissected without impairing its vascular supply, and PtO₂ was measured (PtO₂-30) in the remnant of the angle of his. The stomach was subsequently dissected from adjacencies, and the segment between the distal esophagus and the duodenum was removed totally. The subjects were then sacrificed by administering a high dose of thiopental sodium. The stomach was irrigated, and burst pressure of the gastrectomy line was measured according to the technique implemented by Kuzu et al. (10). A catheter was introduced and fixed with 2/0 silk thread from the duodenum. The distal esophageal end was ligated with 2/0 silk thread to close the lumen. A three-way circuit was established comprising the catheter, the registered gauge, and the arterial blood pressure monitoring system. A flow of 2 mL/min was injected into the circuit until the rupture of the gastrectomy line, and the maximum pressure (mmHg) was recorded at the time of the rupture. Afterwards, a piece of tissue including the EGJ and the proximal gastrectomy line was resected and gently washed. The tissue samples were placed in cryogenic tubes (Cryo.S™, Greiner Bio-One, Frickenhausen, Germany) and kept frozen at -80 °C until the day of hydroxyproline measurement. Hydroxyproline measurement was conducted using a previously described method (11). The principle of the method is the oxidation of hydroxyproline in the samples with chloramine T and the reaction of the oxidized molecule with Erlich reagent to yield a chromophore compound, which can be measured spectrophotometrically. The tissues were weighed and digested with hydrochloric acid in a digestion oven. After the acid digestion, a particular amount of the samples were obtained and placed in a desiccator to allow the liquid to evaporate. The samples were then redissolved in isopropyl alcohol and added with chloramine T and Erlich reagent. After the incubation period, absorbance was recorded at 560 nm. Various concentrations of hydroxyproline were used as standards, and the results were calculated as μg/mg wet tissue. All morbidities and mortalities throughout the procedures were recorded.

Statistical analysis

All groups were compared in terms of PtO₂ levels before, right after, and 30 days after gastrectomy; burst pressure of the gastrectomy line; and hydroxyproline level at the EGJ. Comparisons of PtO₂ measurements, gastrectomy line burst pressures, EGJ tissue hydroxyproline levels, and change ratios of PtO₂ levels among the four study groups were analyzed with Kruskal-Wallis test. For two-group comparisons (12-Fr group vs 8-Fr group) of the same variables, Mann-Whitney U test was used to test for statistical significance. The PtO₂ levels were compared within the same group before, right after, and 30 days after gastrectomy by using Friedman test. When the p value from the Friedman test statistics was statistically significant, multiple comparison test was used to determine which PtO₂ differs (12). Differences were considered to be statistically significant if p values were <0.05. Statistical Package for Social Sciences 16.0 for Windows (IBM Corporation) was used for statistical evaluation.

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