Is the indocyanine green score an accurate predictor of postoperative parathyroid hormone level?

Hypoparathyroidism is common after total thyroidectomy, primarily due to inadvertent disruption of the parathyroid gland blood supply during thyroid dissection. Indocyanine green helps determine the degree of vascularization and correlates with parathyroid gland vitality. It is difficult to determine how the indocyanine green score affects postoperative parathyroid hormone levels because all 4 parathyroid glands must be evaluated during surgery. We determined whether there is a correlation between intraoperative indocyanine green score and postoperative serum parathyroid hormone levels.

We retrospectively studied patients who underwent total thyroidectomy where we could identify all 4 parathyroid glands and establish a global indocyanine green score. Each parathyroid gland was scored from 0 to 2 depending on indocyanine green uptake. The global indocyanine green score was the sum of the individual scores for each gland. The scores were then correlated to parathyroid hormone and calcium levels on days 1 and 10 after surgery.

We included 83 patients, 11 of whom presented with postoperative transient hypoparathyroidism; all but one had an indocyanine green score lower than 4 of 8. There was a significant correlation between the global indocyanine green score and postoperative parathyroid hormone level. A global indocyanine green score >3.75 can exclude postoperative hypoparathyroidism with a true negative value of 98%. Indocyanine green angiography is a better diagnostic test to predict a postoperative transient hypoparathyroidism compared with visual perfusion scoring.

These findings suggest that the indocyanine green score based on intraoperative indocyanine green angiography predicts parathyroid gland function. It is a valuable instrument to predict hypoparathyroidism after total thyroidectomy.