155 Real-time quantification of LSCI during intestinal laparoscopic surgery INTRODUCTION Anastomotic leakage (AL) is one of the most feared complications following colorectal cancer surgery. It negatively impacts surgical outcome, functional results, and quality of life due to reoperation, permanent diversion, or delayed ostomy reversal 1-3. Besides, AL increases the total clinical and economic burden 4. Despite advances in pre-operative risk assessment, operative techniques, and postoperative care, the overall incidence of AL has not significantly decreased over the last decades, with an incidence of 1.5 to 23% and mortality rates as high as 29% 1-3, 5, 6. Several pre-, intra- and postoperative risk factors for colorectal AL have been described 7. The consensus is that sufficient perfusion of tissue is a prerequisite to ensure appropriate anastomotic healing 8-10. An accurate indication of the borderline between the viable and non-viable tissue, i.e. the watershed area, could help surgeons to create optimal anastomosis and mitigate ischemia-related complications 11. Currently, the majority surgeons determine the location of anastomosis based on vital signs of the bowel (e.g., mucosal colour, pulsation in the mesenteric bed, bleeding from resection lines), a subjective strategy that does not take micro perfusion and collateral circulation into account 11-13. Therefore, bowel perfusion assessment is a strategy employed to minimize the risk of AL. At present, most research focuses on bowel perfusion assessment with intraoperative nearinfrared fluorescence imaging (NIRF) using indocyanine green (ICG). However, a more recently developed technique is laser speckle contrast imaging (LSCI). Compared to NIRF, LSCI is a dyefree, non-invasive technique which provides real-time blood flow information by detecting the dynamic interference pattern of laser light on moving red blood cells, known as a speckle pattern 12, 14, 15. Previous studies demonstrated the feasibility of using laparoscopic LSCI to evaluate real-time intraoperative intestinal perfusion 12, 16-18. However, optimization and finetuning of the technology, supported by additional pre-clinical experiments, are necessary to further validate the anticipated clinical usefulness. Although LSCI generates an objective colourmap based on quantitative data to visualize perfusion differences, interpretation of the colourmap remains subjective. The colour on the map does not indicate tissue viability, but flow. Hypothesizing that quantification of data can enhance objectivity and reproducibility, reduce reliance on individual operators, and potentially improve patient outcomes 19-21, the current study was conducted. The objectives of this study were twofold: firstly, to establish a cutoff value for laser speckle perfusion units (LSPUs) indicative of optimal tissue perfusion and viability, aiming to furnish surgeons with quantitative data to enhance clinical decision-making; and secondly, to evaluate inter-observer reliability among both LSCI experts and inexperienced clinicians. Given lactate’s well-established role as a marker for both systemic and local ischemia 22-24, capillary lactate levels were utilized as a reference point in this study. 8
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