Quantitative Fluorescence Angiography With ICG for Perfusion Assessment During Surgery

The accurate assessment of intraoperative tissue perfusion is essential in any branch of surgery. Anastomotic leakage (AL) is one of the most feared complications following gastrointestinal surgery, with potentially threatening consequences resulting in worsened short- and long-term outcomes. Consistently, a recent meta-analysis showed a correlation between AL and shorter disease-free survival in colorectal surgery. Despite its multifactorial origin, AL is highly related to inadequate visceral perfusion. Traditionally, perfusion assessment and subsequent anastomotic viability have been evaluated by surgeons using intraoperative indicators, such as color, pulsation of vessels, presence of peristalsis and bleeding from the resection lines. However, these clinical parameters are not able to reliably assess the real visceral perfusion and their evaluation is limited in minimally invasive surgery. Hence, the growing interest for innovative techniques able to properly assess tissue perfusion. Among these, the fluorescence angiography (FA) with indocyanine green (ICG) has become increasingly popular during the last decade, although its approval for biomedical purposes by the Food and Drug Administration (FDA) dates back to 1956. ICG is an amphiphilic, non-toxic, tricarbocyanine iodide dye that can be safely injected intravenously and is exclusively eliminated by the liver, without any absorption. Thanks to its fluorescent properties, it allows the real-time visualization of tissue vascularization. FA with ICG has shown promising results for the evaluation of perfusion in numerous surgical procedures, thus leading to modifications of the surgical strategy and consequently to a decrease in the rates of AL. On the other hand, ICG interpretation is subjective, based on the evaluation of fluorescence performed by the operating surgeon. These results lack into a high inter-observer variability and affect the possibility to obtain objective, reproducible and reliable tissue perfu