Parathyroid Glands Preservation Using Indocyanine Green Fluorescence in Bilateral Axillo-Breast Approach Robotic Thyroidectomy

Abstract

Background: Bilateral Axillo-Breast Approach (BABA) robotic thyroidectomy (RoT) has shown favorable cosmetic and surgical outcomes since its introduction in 2008. With increasing use of BABA RoT, many trials have been made for effective identification and preservation of parathyroid glands and recurrent laryngeal nerves (RLNs). The aim of this study was to identify and preserve parathyroid glands using indocyanine green (ICG) fluorescence under near-infrared (NIR) light in BABA RoT. Methods: A pilot study of 14 patients was designed to determine an optimal ICG dose. Seven different ICG doses (1 mg, 2.5 mg, 5 mg, 7.5 mg, 10 mg, 15 mg, 20 mg) were assessed for fluorescence patterns and optimal identification time of inferior parathyroid glands. Simultaneous intraoperative tissue parathyroid hormone (PTH) assays were done in 9 patients for biochemical confirmation of assumed parathyroid glands identified by ICG fluorescence. From September 2014 to August 2015, among patients who had undergone BABA RoT due to thyroid cancers, 22 patients were enrolled with informed consents. The patients were given 10 mg ICG intravenously after strap muscle dissection. By Firefly system (NIR illuminator: 805 nm / filter: 825 nm) integrated to da Vinci Si robot system, ICG was excited and emitted green fluorescence. ICG fluorescence duration with optimal identification time of inferior parathyroid glands was estimated from time of its appearance and disappearance in parathyroid and thyroid respectively, with an attempt to find RLN at the same time. Using propensity score matching, control group was set to compare surgical complications between two groups. Patient demographics and clinico-pathologic characteristics were analyzed together. Results: In the pilot study, inferior parathyroid glands were effectively identified with 10 mg ICG at 3 minutes after injection. The results of intraoperative tissue PTH assays suggested successful parathyroid glands identification had been achieved in 9 patients. The mean time taken to visualize parathyroid and thyroid by ICG fluorescence was 203 ± 89 sec (range: 125-331 sec) and 207 ± 112 sec (range: 130-356 sec) with mean fluorescence duration of 20.8 ± 6.0 min (range: 16.6-35.8 min) and 20.1 ± 7.3 min (range: 15.5-33.8 min) respectively. All 32 parathyroid glands of 22 patients were distinguished from thyroid by earlier enhancement, more focal and intense fluorescence pattern. RLNs didn't show ICG fluorescence in contrast to thyroid and parathyroid glands. In postoperative period mild transient hypoparathyroidism was reported in one patient, otherwise no RLN palsy occurred. ICG group showed significantly lower rates of transient hypoparathyroidism (4.5 % vs 50 %, P < 0.001) and incidental parathyroidectomy (0 % vs 38.6 %, P < 0.001) compared to control group. Conclusions: The results of the present study suggest that parathyroid glands preservation using ICG fluorescence under NIR light may be feasible and safe in BABA RoT. RLNs were also easily detected and saved by means of its non-fluorescent property.