Time to maximum indocyanine green fluorescence of gastric sentinel lymph nodes and feasibility of combined indocyanine green/sodium fluorescein gastric lymphography

Purpose Indocyanine green (ICG) and sodium fluorescein (SF) are fluorescent dyes used for sentinel lymph node mapping. In oncological gastric surgery, ICG lymphography has increased the number of resected lymph nodes. However, the optimal time to administer ICG is unclear, and both preoperative and intraoperative injections have been practised. As dye spillage will diminish lymphogram visibility, a second dye with different excitation and emission spectra may present a clinical alternative. We measured the time until maximum ICG fluorescence of gastric sentinel lymph nodes and investigated the feasibility of combined lymphography with two fluorescent dyes: ICG and SF. Methods Ten Danish Landrace/Yorkshire pigs were used in this study. After completion of the laparoscopic setup, ICG and then SF were endoscopically injected into the gastric submucosa. Lymphograms for both dyes were recorded, and the time until maximum ICG sentinel lymph node fluorescence was determined. Results The mean time until maximum ICG fluorescence of gastric sentinel lymph nodes was 50 s (+/- 12.5), and the fluorescent signal then remained stable until the end of the recorded period (45 min). A lymphogram showing both ICG and SF was acquired for eight of the ten pigs. Conclusions Because of the short time until maximum ICG fluorescence of sentinel lymph nodes, intraoperative injections could be a sufficient alternative to preoperative injections for oncological gastric surgery. Combined ICG and SF lymphography was feasible and resulted in clear lymphograms with no interference between the two dyes. The ability to use multiple dyes during a surgical procedure offers the exciting prospect of simultaneously assessing perfusion and performing fluorescence lymphography.

Automated summary

ICG lymphography significantly increased the number of resected lymph nodes in oncological gastric surgery. Intraoperative injections of ICG could be a sufficient alternative to preoperative injections due to the short time until maximum ICG fluorescence of sentinel lymph nodes. Combined ICG and SF lymphography was feasible and resulted in clear lymphograms with no interference between the two dyes, offering the exciting prospect of simultaneously assessing perfusion and performing fluorescence lymphography.