Intraoperative Indocyanine Green Angiography of Parathyroid Glands and the Prevention of Post-Thyroidectomy Hypocalcemia

Comparison of indocyanine green angiography vs intraoperative parathyroid hormone in early prediction of risk of post-thyroidectomy hypocalcemia: a prospective cohort study

Introduction

Indocyanine green (ICG) angiography is the 'real-time intraoperative imaging' technique used to reduce the chances of hypoparathyroidism in post-thyroidectomy patients. In our study, the authors predicted the risk of early post-thyroidectomy hypocalcemia by intraoperative evaluation of parathyroid gland perfusion by ICG angiography.

Materials and methods

In patients who underwent total thyroidectomy, ICG angiography was done using the SPY PHI imaging system (Stryker). Post-thyroid specimen removal, scoring of parathyroids was done in spy contrast mode. All 4 or <4 visualized parathyroids were scored for vascularity with the highest score of 8. Serum ionized calcium was done 6 h postsurgery and on the morning and evening of postoperative days 1 and 2. Calcium supplements were given to only those who developed clinical or severe biochemical hypocalcemia.

Results

Out of 60, postoperative hypocalcemia was noted in 41 patients. Total ICG score ≤5 was seen in 34 patients, out of which 28 developed postoperative hypocalcemia showing PPV 82.3% and diagnostic accuracy of 68.3% while iPTH (4.28 pmol/l) showed PPV 76.7 and diagnostic accuracy 70 %. In eight patients, none of the glands was scored as 2 (White) and all these patients developed hypocalcemia requiring calcium infusion.

Conclusion

The absence of visualization of at least 1 well-perfused (score 2) gland on ICG angiography is highly predictive of hypocalcemia and the majority of patients with total ICG score ≤5 developed hypocalcemia in the immediate postoperative period. ICG is a good predictor of the absence of hypoparathyroidism after thyroidectomy and is comparable to iPTH in the prediction of post-thyroidectomy hypocalcemia.

Correlation between visual scores and parathyroid function

This mini review summarizes the controversies regarding routine parathyroid identification reviews publications that assess visual scores to predict parathyroid function after thyroidectomy during the pre-ICG era.

Indocyanine green angiography-guided thyroidectomy versus conventional thyroidectomy for preserving parathyroid function: study protocol for a randomized single-blind controlled trial

Introduction

Angiography with indocyanine green (ICG) fluorescence performed before thyroidectomy would allow identification of the vascularization of parathyroid glands, maximizing efforts for preserving functioning glands intraoperatively. The rationale of the study was based on the hypothesis that showing the vascular pattern of the parathyroid glands by means of ICG angiography before performing the thyroidectomy could prevent permanent hypoparathyroidism.

Methods and analysis

We propose a randomized single-blind controlled and multicenter clinical trial to assess the efficacy and safety of ICG angiography-guided thyroidectomy to identify the vascular pattern of the parathyroid glands versus conventional thyroidectomy in patients scheduled for elective total thyroidectomy. Patients will be randomized 1:1 to ICG angiography-guided thyroidectomy (experimental group) or conventional thyroidectomy (control group). Patients in the experimental group will undergo ICG angiography before thyroidectomy to identify the feeding vessels of the parathyroid glands and then, post-thyroidectomy ICG angiography to predict immediate parathyroid gland function by scoring the degree of fluorescence of the glands. Patients in the control group will undergo post-thyroidectomy ICG angiography only. The primary outcome measure will be the rate of patients with permanent hypoparathyroidism. Secondary outcome measures will be rate of postoperative hypoparathyroidism, the percentage of well vascularized parathyroid glands remaining in situ, the levels of iPTH and serum calcium after surgery and the influence of the type of vascular pattern of the parathyroid glands over these outcomes, as well as the safety profile of ICG angiography.

Discussion

The results will contribute to adopt a new surgical strategy based on intraoperative ICG angiography before performing total thyroidectomy, according to which the rate of permanent hypoparathyroidism could be substantially reduced.

Clinical trial registration

ClinicalTrials.gov. identifier NCT05573828.

Usefulness of ICG Angiography-Guided Thyroidectomy for Preserving Parathyroid Function

INTRODUCTION

Hypoparathyroidism is the most frequent complication after total thyroidectomy and, when permanent, it becomes a severe chronic disease. We assessed the usefulness of indocyanine green (ICG) angiography-guided thyroidectomy to reduce the postoperative hypocalcemia.

METHODS

Prospective study with two consecutive cohorts of patients who underwent total thyroidectomy: historical control group (CG) and angiography-guided thyroidectomy group (AG). In all patients, ICG-angiography was performed at the end of the surgery to predict immediate parathyroid gland (PG) function. In the AG, ICG-angiography was also done after PG identification to show their vascular supply. We compared the rate of postoperative hypocalcemia (calcium supplementation needed due to hypocalcemia symptoms or calcium levels < 1.8 mmol/L on the first postoperative day) and permanent hypocalcemia (need of calcium ± vitamin D supplementation 12 months after thyroidectomy).

RESULTS

We included 120 consecutive patients (84 CG; 36 AG). Thyroid cancer was the most common diagnostic (63.1% CG-69.4% AG; p = 0.646) and central neck dissection was also frequent (54.8% CG-64.3% AG; p = 0.468). The AG developed a lower rate of postoperative (26.2-5.6%; p = 0.011) and permanent hypocalcemia (11.9-0%; p = 0.032). The OR for permanent hypocalcemia was 0.673 (95% CI 0.591-0.766). A significant higher rate of well vascularized PG at the end of the surgery (score 2) in the AG (39.2-52.9%; p = 0.018) was also seen.

CONCLUSION

ICG angiography-guided thyroidectomy is a useful tool to identify PG vascularization, allowing a better PG preservation and a significant decrease in hypocalcemia rates.

Indocyanine green fluorescence and near-infrared autofluorescence may improve post-thyroidectomy parathyroid function

BACKGROUND

Near-infrared autofluorescence and indocyanine green fluorescence are 2 recent tools introduced to improve postoperative parathyroid function during thyroid surgery.

METHODS

We conducted a randomized prospective study. Patients undergoing total thyroidectomy were randomly assigned either to the fluorescence group, in which near-infrared autofluorescence and indocyanine green fluorescence were used, or to the control group. The primary outcomes of the study were the rate of postoperative transient and symptomatic hypocalcemia.

RESULTS

A significantly higher number of parathyroid glands were identified in the fluorescence group (3.83 vs 3.64, P = .028). The rate of postoperative symptomatic hypocalcemia was significantly lower in the fluorescence group (6% vs 17%, P = .015), as was the dosage (1.53 vs 1.91 g, P = .007) and the duration of calcium therapy (32.30 vs 45.66 days, P = .003). Having at least 2 well-vascularized parathyroid glands correlates to lower rates of transient hypocalcemia (7.4% vs 21.9%, P = .037) as well as to higher serum calcium (8.70 vs 8.42 mg/dL, P = .027) and parathyroid hormone levels (19.15 vs 11.4 pg/mL, P = .0002) on postoperative day 1.

CONCLUSION

Near-infrared autofluorescence and indocyanine green fluorescence are novel tools that may support the endocrine surgeon in preserving and predicting post-thyroidectomy parathyroid gland function.

Indocyanine Green Angiography of Parathyroid Glands versus Intraoperative Parathyroid Hormone Assay as a Reliable Predictor for Post Thyroidectomy Transient Hypocalcemia

BACKGROUND

Prediction of postoperative hypocalcemia is a fundamental issue in thyroidectomy. Indocyanine green (ICG) angiography of parathyroid glands is a feasible method to detect the perfusion of parathyroid glands and predict postoperative hypocalcemia.

MATERIALS AND METHODS

A prospective observational study was conducted at Ain Shams University Hospitals between April 2018 and April 2021. The included cases of total thyroidectomy underwent intraoperative ICG fluorescence angiography to identify the four parathyroid glands and score each gland according to the viability. Patients in which less than four glands were identified were excluded. Intraoperative intact parathyroid hormone (ioPTH) level assay was also measured to compare with ICG in predicting postoperative transient hypocalcemia.

RESULTS

A total of 134 cases underwent total thyroidectomy during the study period. We could identify the four parathyroid glands in 90 patients, including them in the study. We had postoperative hypocalcemia in 28 cases (31.1%). The diagnostic accuracy of ICG angiography and ioPTH level assay was high and almost similar (82.22% versus 87.78%). Both were higher than the surgeons' diagnostic accuracy of visual inspection (62.22%).

CONCLUSIONS

ICG angiography of the parathyroid gland is a safe, reliable predictor for postoperative transient hypocalcemia with a high and almost similar accuracy compared to intraoperative parathyroid hormone level.