Determining the level of resection of the intestine in experimental acute intestinal obstruction using bioimpedance

Abstract

Relevance. One of the most important stages during surgical treatment of acute intestinal obstruction is the determination of irreversible damages of the intestine. The aim of this study was to improve outcomes of surgical treatment of acute intestinal obstruction through the reducing of a removable part of the intestine during bowel resection in the case of its necrosis. Materials and methods. An experimental investigation was performed on 64 Wistar rats 180-230 g. Medial laparotomy was carried out on animals and acute strangulation intestinal obstruction in the small intestine was modeled by applying a thick ligature onto the small intestinal loop 1,5-2,0 cm long together with the mesentery. The pathological process was created for periods of 1 h (n=11), 3 h (n=13) and 6 h (n=12). The normal level of the impedance of the intestine wall on 13 rats was found. Another group of animals contained 15 rats with modeled strangulation obstruction in the small intestine. Pathological process was created for a period of 3 h. The small intestinal segments were then resected at different distances from strangulation site and anastomoses were formed. Invasive bioimpedancemetry was performed by a device “BIM-II” for measuring the electrical impedance of biological tissues (Patent of Russian Federation № 2366360). The measurement of the impedance of physiological solution in vitro was performed as a test of the device. After bioimpedancemetry histological examination was performed. Results and discussion. The impedance index of physiological solution was 0,46 kΩ. Study of changes in impedance indices in the afferent and efferent portions of the small intestine showed that the indices decreased towards the strangulation zone, the lowest indices recorded at the interface of the strangulation zone. Histological examination of the small and large intestine in zones with impedance indices below 2 kΩ in the course of acute intestinal obstruction showed signs of necrosis of different severity. The maximum impedance level in these regions was 1.99 kΩ. No signs of necrosis were detected in the intestinal zones with impedance above 2 kΩ, irrespective of the period of the pathological process. The impedance index above 2 kΩ served as the criterion for resection of the intestine. Histological examination of the intestinal anastomoses created in resection of the intestine in the course of acute intestinal obstruction with consideration for impedance indices and of anastomoses created in resection of the organ within a priori viable tissues showed no appreciable differences in the histomorphology of healing. Conclusions. The impedance index of the intestinal wall of afferent and efferent portions of the intestine above 2 kΩ in the course of acute intestinal obstruction served as a criterion for determination of the level for resection of the intestine. Key words: experiment, acute intestinal obstruction, viability of the intestine, bioimpedancemetry.