Indocyanine green fluorescence during total thyroidectomy: utility for predicting hypoparathyroidism and safety assessment

Abstract Purpose Parathyroid fluorescence with indocyanine green (ICG) might prevent and predict postoperative hypoparathyroidism (hypoPT) after total thyroidectomy (TT). We aimed to evaluate parathyroid gland vascularization with ICG during TT. Further, we aimed to evaluate safety of ICG fluorescence and to correlate changes in PTH with postoperative hypoPT after TT. Methods From May 2021 to June 2023, consecutive patients underwent TT and parathyroid fluorescence with ICG. Each visible parathyroid gland was scored 0, 1 or 2 depending on fluorescence intensity. Patients with at least one gland score of 2 were compared to those without. We measured PTH before and after TT, changes in calcium, creatinine and alanine transaminase (ALAT), postoperative alfacalcidol requirements, and adverse events of ICG use. Results A total of 124 patients were included. Patients with at least one gland scored 2 ( n = 108) had a reduced need for alfacalcidol at discharge compared with those without (8% vs. 38%, p = 0.004), although hypoPT was not fully excluded. Six patients required alfacalcidol after 12 months and were classified as having permanent hypoPT; all had an intraoperative PTH decrease > 83%. Creatinine levels were higher in patients with permanent hypoPT compared to others ( p = 0.01). No increases in ALAT or ICG-related adverse events were observed. Conclusions ICG-based parathyroid fluorescence during TT was well tolerated in this cohort and predicted immediate postoperative hypoPT. However, a fluorescence score of 2 did not exclude hypoPT development. The grading system is limited by subjectivity. No permanent hypoPT occurred in patients with a PTH decrease ≤ 83% after TT.