LAUSR

The ability to assess tissue perfusion and identify vital structures in the operating room in order to potentially decrease complication rates remains a key goal for surgeons. The introduction of immunofluorescence utilizing indocyanine green intraoperatively to evaluate areas such as an anastomosis, a free flap, biliary anatomy, or lymphatics has the possibility of decreasing postoperative complications by addressing identification and perfusion concerns at the time of surgery. The use of laser-induced immunofluorescence using indocyanine green relies on similar principles as fluorescein technique, which was first proposed in 1942. Fluorescein angiography was initially used to evaluate vascularity of the eye and skin. Fluorescein angiography did not become clinically significant, however, due to difficulties with the tracer. Indocyanine green, a secondgeneration tracer, was developed in order to overcome the limitations of fluorescein. Indocyanine green (ICG) is a water-soluble lyophilized powder with a chemical formula of C43H47N2O6S2Na. It is a fluorophore that responds to near-infrared irradiation and absorbs light between the wavelengths of 790 and 805 nm and re-emits it with an excitation wavelength of 835 nm. The compound is administered intravenously, and when injected it binds to plasma proteins. ICG binds nearly exclusively to albumin on electrophoresis, with only minor binding to other serum proteins, as shown in Table 1 [1]. It is then taken up in the liver and excreted in bile. The half-life of ICG is 3–5 min and excreted by the liver in 15–20 min. Its short half-life, hepatic excretion, and unique wavelength emission in tissue providing images of both circulation and lymphatics make it well suited for use in the operative field. Contraindications for use of ICG are limited, but include patients with a known allergy or adverse reaction to ICG or iodine and those women who are pregnant or lactating. There have been reports of rare cases of anaphylactic shock and urticaria associated with ICG usage. ICG and Near-Infrared (NIR) imaging modalities have been used in a wide array of surgical procedures. Minimally invasive colorectal surgery, encompassing both laparoscopic and robotic techniques, has employed the use of immunofluorescence to evaluate the perfusion of the anastomosis. This includes anastomoses for colorectal cancer of the right and left colon, as well as rectal cancer resections. Further immunofluorescence imaging has been used to assess blood supply of anastomoses following pancreaticoduodenectomy and esophagectomy. Additional uses of this technology in general surgery include lymphadenectomy, donor nephrectomy, and liver resection to evaluate perfusion, and biliary anatomy during cholecystectomy. Fluorescence-guided surgery has been utilized in oncology surgery in attempts to achieve improved marginnegative status [2] although this analysis will not cover this use as it is outside of the focus of this evaluation. Finally, immunofluorescence has been used with some success in & David Renton [email protected]