Identification of the ideal weight-based indocyanine green dose for fluorescent cholangiography.

Background: Ideal visualization of fluorescent cholangiography during laparoscopic cholecystectomy is when maximum fluorescence into biliary ducts and absent signal into liver parenchyma, defined as "signal to background ratio" (SBR), is obtained. Such condition is mainly dependent by indocyanine green (ICG) dose and timing. The aim of this study was to identify the ideal ICG dose to obtain the best possible intraoperative visualization of the extra-hepatic biliary tree.

Methods: The first part of the study was used to define a range of small weight-based ICG dosages using the mathematical function bisection method. During the second part of the study, the midpoint dose of the identified range, was tested in 50 consecutive cholecystectomies using a laser-based fluorescence laparoscopic camera (Synergy system by Arthrex, Naples, FL, USA). Timing administration was set at 1 h before surgery, since this is the most common situation in clinical practice. Fluorescence intensity of bile ducts and liver parenchyma were assessed both subjectively, by blinded operative surgeon, as well as objectively, using an image analysis software (Fiji plugin), before and after Calot's triangle dissection.

Results: Fourteen patients were included in the first part of the study and ICG dose between 0.01191406 and 0.0119873 mg/kg was identified. The second part confirmed previous results after testing the dosage equal to 0.0119 mg/kg (midpoint of the defined range) in 50 consecutive cholecystectomies. Cystic duct was identified in 66 and 100% of cases before and after dissection of Calot's triangle respectively. On the other hand, common bile duct was identified in 82 and 92% before and after dissection respectively. Subjective and objective SBRs confirmed the benefit of the identified ICG dose.

Conclusion: ICG dose calculated by 0.0119 mg/kg administered one hour before surgery allows an ideal intraoperative visualization of the extra-hepatic biliary tree.

Registration Number: ISRCTN10190039.