Efficacy of Fluorescein Green Dye in Assessing Intra-Operative Parathyroid Gland Vascularity and Predicting Post-Thyroidectomy Hypocalcaemia- A Novel Prospective Cohort Study

BACKGROUND: Postoperative hypocalcaemia (POH) after total thyroidectomy (TT) is a common complication. Parathyroid hormone (PTH), an accurate predictor of POH cannot assess intra-operative viability of parathyroid glands (PGs). Different dyes including indocyanine green or carbon nanoparticles have been used, but they are expensive and not widely available. Fluorescein green dye (FD) has been used as a low-cost alternative to study viability of various organs, but seldom tried in visualizing PGs. This novel study aims to assess utility of FD in determining parathyroid viability and predicting POH. MATERIAL AND METHOD: Total 72 out of 88 patients undergoing TT between January and December 2019 were included. Two ml of 25% FD was given intravenously before wound closure and attempts were made to visualize PGs under blue light. A numerical score was given according to the number of PGs visualized. Intact-PTH and corrected calcium were measured on postoperative day 1 and patients observed for POH. RESULTS: No PGs were visualized in 6 patients, 1 in 13, 2 in 30, 3 in 16 & 4 in 7 patients. Mean PTH was 6, 16.9, 31.6, 33.2 and 48.5 respectively. Corrected-calcium was 7.08, 7.7, 7.9, 8.5 and 8.5 respectively. All patients with score 0 received supplementary IV calcium, while 53.8% (score-1), 30% (score-2), 0% (scores-3, 4) received the same. Sensitivity, specificity and ROC of PG score of ≥2 on FD in predicting POH were 100%, 44% and 0.83 respectively. CONCLUSION: FD visualization of parathyroids post TT is feasible and can be used as low cost efficacious method to predict POH.