When Should Indocyanine Green Be Assessed in Colorectal Surgery, and at What Distance from the Tissue? Quantitative Measurement Using the SERGREEN Program

Background: Suture dehiscence is one of the most feared postoperative complications. Correct intestinal vascularization is essential for its prevention. Indocyanine green (ICG) is one of the methods used to assess vascularization, but this assessment is usually subjective. Our group designed the SERGREEN program to obtain an objective measurement of the degree of vascularization. We do not know how long after ICG administration the fluorescence of the tissues should be evaluated, or how far away the measurement should be performed. The aim of this study is to establish the optimal moment and distance for analyzing the fluorescence saturation of ICG.

Methods: Prospective observational study in patients undergoing elective laparoscopic colorectal surgery. The optimal time for ICG analysis was tested in a sample of 20 patients (10 right colon and 10 left colon), and the optimal distance in a sample of ten patients. ICG was administered intravenously, and colon vascularization was quantified using SERGREEN; RGB (Red, Green, Blue) encoding was used. The intensity curve of the ICG was analyzed for ten minutes after its administration. Distances of 1, 3, and 5 cm were tested.

Results: The intensity of fluorescence increased until 1.5 min after ICG administration (reaching figures of 112.49 in the right colon and 93.95 in the left). It then remained fairly stable until 3.5 min (98.49 in the right and 83.35 in the left), at which point it began to decrease gradually. ICG saturation was inversely proportional to the distance between the camera and the tissue. The best distance was 5 cm, where the confidence interval was narrower [CI 86.66-87.53].

Conclusion: The optimal time for determining ICG in the colon is between 1.5 and 3.5 min, in both right and left colon. The optimal distance is 5 cm. This information will help to establish parameters of comparison in normal and pathological situations.