329 Summary, general discussion and future perspectives by laser light interacting with moving red blood cells, referred to as a speckle pattern 46. Using a camera during surgery, fluctuations in the speckle contrast pattern can be interpreted as alterations in perfusion 47. Although NIRF has been extensively studied in colorectal surgery setting as presented in the previous chapters, LSCI remains relatively untested in clinical environments. Nevertheless, LSCI offers inherent benefits such as ongoing assessment of tissue perfusion and independence from contrast agents and was therefore investigated in chapter 7 and 8. Chapter 7 investigated the potential of LSCI to offer insights into tissue perfusion states and the real-time assessment of intestinal anastomotic perfusion. The study focused on a socalled red flag technique to guide surgeons in the creation an anastomosis using optimally perfused tissue. Utilizing a Landrace pig as the experimental subject, three small bowel loops with gradually varying perfusion levels were generated and shown to surgeons. The findings showcased a high level of accuracy in identifying compromised perfusion and discerning perfusion variations among the loops using LSCI feedback. Furthermore, the study assessed the influence of LSCI on the decision-making process related to anastomosis creation. The visual feedback provided by LSCI led all surgeons to advise against creating an anastomosis, underscoring its potential to steer surgeons away from inadequately perfused tissue segments. A survey on usability highlighted the satisfaction of senior surgeons with LSCI as a perfusion imager. Chapter 8 aimed to establish a preliminary threshold for laser speckle perfusion units (LSPUs) to gauge tissue perfusion and viability, aiming to equip surgeons with quantitative data for clinical decision-making. Four mature female Landrace pigs were employed in this study. The surgeon identified ischemic and well-perfused areas, along with watershed regions, based on the color map provided by LSCI. Local capillary and systemic lactate levels were also measured alongside LSCI recordings. Mean LSPUs significantly decreased over time in ischemic areas (P≤.001) and watershed areas (P≤.001), while no significant change was noted in well-perfused areas over a two-hour period. Changes in LSPUs correlated with alterations in lactate levels in both ischemic and well-perfused tissues. Logarithmic curve estimation revealed an R² value of 0.56 for the correlation between LSPUs and local capillary lactate levels. The cut-off value for LSPUs was determined to be 69 AU with a sensitivity of 0.94 and specificity of 0.87 (Youden index 0.81), indicating well perfused tissue. Subsequently, a cut-off value of 3.8 mmol/L for lactate effectively indicated well perfused tissue, with a sensitivity of 0.97 and specificity of 1.00 (Youden index 0.97). A post-hoc inter-rater reliability analysis comparing a group of LSCI experts with the operating surgeon yielded a substantial Kappa of 0.66, and comparison between physicians and the surgeon resulted in a moderate Kappa of 0.56. The comparison between the whole observer group and the surgeon showed a moderate Kappa of 0.52 (95% 0.44-0.61). Overall, this study suggested that LSCI holds promise as a contender for current perfusion visualization techniques, but further research on real-time quantification of LSPUs and clinical applicability is imperative. 14
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