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Background: Assessing perfusion in free flaps is crucial in clinical practice. Indocyanine green (ICG) angiography offers a more objective and reproducible method, utilizing near-infrared imaging to monitor flap vascularization. This study aims to evaluate the efficacy of diluted ICG as a tool for assessing free flap perfusion., Methods: This pilot randomized clinical trial compares the fluorescence concentrations of ICG at 3 different dilutions: 5 mg/mL (standard concentration), 2.5 mg/mL (half the standard concentration), and 0.5 mg/mL (one-tenth of the standard concentration). Inclusion criteria required participants to have serum albumin levels above 3 g/dL, hemoglobin levels over 10 g/dL, and no comorbidities. Participants were randomized into 3 groups based on ICG concentration. Fluorescence analysis was performed using ImageJ software to determine mean gray values. Both surgeons and data analysts were blinded to the ICG concentrations administered, ensuring unbiased evaluation., Results: Forty-five patients undergoing free flap surgery, predominantly male (60%) with a mean age of 37.76 ± 19.79 years and a mean body mass index of 21.23 ± 4.49 kg/m², primarily received osteoseptocutaneous fibular free flaps (46.67%), with an average skin flap area of 66.07 ± 46.94 cm². The primary etiology was underlying tumors (84.4%), with the head and neck as the most common reconstruction site (82.2%). The superior thyroid artery was the most frequently used recipient vessel (37.78%). Analysis revealed mean gray values of 64.10 ± 8.27 (5 mg/mL), 79.03 ± 2.7 (2.5 mg/mL), and 33.56 ± 3.47 (0.5 mg/mL), with 2.5 mg/mL yielding the highest value ( P < 0.001)., Conclusions: Findings suggest using 2.5 mg/mL concentration enhances fluorescence emission, offering a dosage alternative in clinical practice., Competing Interests: The authors have no financial interest to declare in relation to the content of this article. This work was supported by PUTI Q2 Grant from Universitas Indonesia. Disclosure statements are at the end of this article, following the correspondence information., (Copyright © 2024 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of The American Society of Plastic Surgeons.)

The ideal dose for indocyanine green (ICG) has not been established yet, although 5 mg per mL is widely accepted for free flap evaluation. Due to its high price and rarity in developing countries, this preliminary study aimed to find the lowest concentration of ICG without reducing the fluorescence quality read by near-infrared camera in animal models. An experimental study was conducted on 25 Wistar rats divided into five groups based on the injected ICG, which was in 5 mg per mL, 3.75 mg per mL, 2.5 mg per mL, 1.25 mg per mL, and 0.5 mg per mL concentrations. The epigastric flap was elevated and confirmed to be vital on the fifth day. Upon confirmation, bolus IV injection of ICG was given via the tail, and the flap was read using near-infrared camera. The 25 different videos are randomized and rated individually in a blind manner by five microsurgeons, chosen beforehand. The videos are evaluated with a scoring system ranging from 0 to 4, assessing fluorescence visibility and flap vasculature. Nonetheless, the intraclass correlation coefficient is 0.779. There was no difference between standard and diluted ICG concentrations to evaluate flap perfusion. The 2.5 mg per mL concentration of ICG was the most favorable. This finding is not clinically relevant for application in human subjects yet. However, this study shows promising results for further usage of ICG in daily practice at a lower cost., Competing Interests: The authors have no financial interest to declare in relation to the content of this article., (Copyright © 2024 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of The American Society of Plastic Surgeons.)