156 Chapter 8 MATERIALS AND METHODS Animals and surgical procedure This animal study was performed at the Central Animal Facilities of Maastricht University (Maastricht, The Netherlands). A total of four mature female Landrace pigs were used for this study, in compliance with the regulations of the Dutch legislation concerning animal research, ARRIVE guidelines and with approval from a local animal ethics committee (DECUM; Number: 2017-021-001). All surgical interventions were conducted with the administration of general anaesthesia. An intravenous combination of medications, including 6mg/kg Zoletil, 0.01 mg/kg/h sufentanyl (Hameln Pharma GmbH, Hameln, Germany), 9 mg/kg/h propofol (B. Braun Melsungen AG, Melsungen, Germany), and 1 mg/kg/h midazolam (Aurobindo, Baarn, The Netherlands), was administered for anaesthesia induction. Throughout the procedure, all animals underwent mechanical ventilation to ensure adequate respiration. Ventilation settings were adjusted when necessary to maintain optimal oxygenation and ventilation. Continuous infusion of sufentanyl and propofol was used to sustain anaesthesia, with additional doses administered as required during the procedure. At the conclusion of the experiment, euthanasia was performed using a lethal dose of 200 mg/kg Pentobarbital (AST Farma, Oudewater, The Netherlands). A midline laparotomy was performed by an experienced surgeon and small bowel loops of approximately 20 cm in length were randomly selected. Subsequently, a minimum of eight consecutive mesenterial arteries feeding the loop were identified and ligated using an energy device (Thunderbeat, Olympus, Hamburg, Germany) to induce ischemia. Laser Speckle Contrast Imaging A PerfusiX-Imaging® device (LIMIS Development BV, Leeuwarden, The Netherlands) was used to perform laparoscopic LSCI, as described by Heeman et al. 17. This is a laparoscopic perfusion imager that functions as an add-on with a range of widely clinically available laparoscopic video equipment. In this study, an OTV-S200 laparoscopic video system (Olympus, Hamburg, Germany) and a 30-degree chip-on-the-tip laparoscope (EndoEye, Olympus, Hamburg, Germany) were used in combination with the investigational device. This setup is capable of instantaneously providing real-time perfusion maps of intestinal tissue using a red laser source. A proprietary mechanism in the device allows switching between the original white light source and the visible red laser light. LSCI is based on changes in the speckle pattern that arise when illuminated tissue contains moving particles 25. The level of moving particles (i.e. red blood cells) affects the changes in speckle contrast, allowing for calculation and visualization of perfusion levels through 2D-perfusion maps on the surgical monitor. The colourmap shows a gradient between blue (relatively low perfusion) and yellow (relatively good perfusion), based on LSPUs (arbitrary units, or AU). LSPU’s were calculated by the ratio of the standard deviation (SD) divided by
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