130 Chapter 6 precipitate serotonin toxicity if combined with other serotonergic drugs at doses above 5 mg/kg 18. When levels are >7 mg/kg, many of the adverse effects occur 16, 17, 19. Refractory hypotension and skin discoloration are only known upon administration of 20 to 80 mg/kg 17, and anaphylactic reaction is extremely rare 9. As the previous mentioned doses are much higher than needed for bowel perfusion assessment as demonstrated in this study, such adverse events are not expected for this indication. It is important to know that MB is contraindicated together with serotonergic drugs, in glucose-6-phosphate dehydrogenase deficient patients, in patients with renal failure, and in pregnant women 9, 16. Compared to ICG, MB has some more adverse reactions when administered in higher doses, but is currently completely safely used for visualization of thyroid and parathyroid glands, pancreatic neuroendocrine tumors, and breast cancer tumors and sentinel nodes within doses of <2 mg/kg 9. Although the use of ICG fluorescence is recommended in colorectal surgery to assess tissue perfusion 4, there is still no consensus on how to quantify fluorescence angiography. Previous studies were conducted to establish and gather validity evidence for a method of quantifying fluorescence angiography 20-24. This revealed that bowel perfusion quantification is a feasible method to differentiate between different perfusion patterns, highlighting the possibility of using standardized imaging protocols 21. According to a recent consensus paper on ICG fluorescence angiography, we concur with the authors’ standpoint that additional investigation into quantitatively evaluating fluorescence is imperative. This will help to reduce the subjective variability associated with perfusion assessment 4, and make it easier to compare study outcomes with different dyes, and will improve the validity and reproducibility of such data in daily practice. The unique aspect of the present study is that, to our knowledge, no previous study has demonstrated the use of MB for bowel perfusion imaging in addition to the well-known and widely used ICG, within a single operative procedure and with a single commercially available NIRF imaging system. Based on the findings presented in this study and our previous investigations 8, 25, we can conclude that MB, when used in a dedicated imaging system, offers a range of simultaneous and multipurpose functionalities, all achieved solely through the administration of a single dose of MB. Based on several studies and recent consensus papers, the incorporation of ICG fluorescence for perfusion assessment during colorectal surgery has been shown to substantially decrease the risk of AL 2, 4, 14, 26. It can even result in modifications to the resection line and/or adjustment of the anastomosis, and leads to shorter hospital stay and reduced overall morbidity 4. ICG fluorescence highlights the added value of performing NIRF for bowel perfusion assessment. Considering that fluorescence imaging is not currently used in all medical facilities routinely, we anticipate that the findings from this study, along with our previous research, will encourage clinicians to explore the use of MB fluorescence. The advantage of using a single dye for multiple purposes makes it an appealing option for clinical practice.
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