Bilateral Truncal Ligation of the Inferior Thyroid Artery during Bilateral Subtotal Thyroidectomy Causes a Decrease in Parathormone without Clinically Manifest Hypoparathyroidism: A Randomized Clinical Trial

Abstract

Background: Bilateral truncal ligation (BTL) of the inferior thyroid artery (ITA) is frequently used during subtotal thyroidectomy to reduce the risk of post-operative bleeding as well as to reduce the blood loss intra-operatively. However, its effect on parathyroid function has not been evaluated in relation to age, residual and resected thyroid volume. Methods: A total of 83 patients were randomized to receive non-BTL or BTL. After bilateral resection, the residual thyroid tissue on each side was measured by intra-operative ultrasonography. Laboratory and clinical examinations were performed the day before operation, intra-operatively and on post-operative days 2 and 5. The primary outcome measure was the difference in intact parathormone (PTHi) on post-operative day 5. Secondary outcomes were laboratory-diagnosed hypocalcaemia or hypoparathyroidism and clinically manifest hypoparathyroidism, respectively. Results: PTHi on post-operative day 5 was significantly lower in the BTL group (29.4 vs. 34.7 ng/l in the non-BTL group, p = 0.033), especially in 61- to 80-year-old patients (0 vs. -7.91 ng/l, p = 0.029). The biggest decline in PTHi was found in the BTL group (-14.067 ng/l PTH, p = 0.018) with a residual thyroid volume of 0.5-1.9 ml. There were two cases of asymptomatic hypoparathyroidism in each group (5.1 vs. 4.8%, respectively, p = 1.000). The only case of clinically manifest hypoparathyroidism was in a BTL group patient aged 64 years (2.4%, p = 1.000). Conclusion: BTL of the ITA during subtotal thyroidectomy causes a larger decrease in PTH but does not lead to a significantly higher rate of clinically manifest hypoparathyroidism. BTL of the ITA, age >61 years, and a very small thyroid remnant (<2 ml) may be risk factors for post-operative hypoparathyroidism.

Inferior thyroid artery ligation increases hypocalcemia after thyroidectomy: A meta‐analysis

“…Four studies measured serum calcium levels 2 days postoperatively, whereas the other researchers measured it up to 5 days postoperatively. The time to follow‐up was 6 months in five studies and longer than 6 months in the others. Seven studies did not report time to long‐term follow‐up…”

“…We found 11 NRCTs and nine RCTs . The characteristics of the studies are shown in Supporting Table in the online version of this article.…”

“…As more than 80% and 90% of the blood supply of the superior and inferior parathyroid glands, respectively, is provided by the inferior thyroid artery (ITA), some authors have proposed mandatory ligature of secondary and tertiary branches of the ITA medial to the gland to avoid the ligature of truncal arteries to prevent postoperative hypocalcemia . However, since the original Wade et al study, some authors have not found differences in the rate of hypocalcemia using this technique …”

Hypocalcemia: What a Surgeon should know

“…7 Studies have also demonstrated that vasculature-preserving techniques reduce the risk of postoperative hypocalcemia. 26 Most experts believe that the surgeon's skill and experience can affect the occurrence of postoperative hypocalcemia. 27 Indeed, this was first evident when patients who underwent TT by Theodor Kocher, using his principles of bloodless surgery, had a lesser incidence of postoperative hypocalcemia as compared with those operated by Billroth.…”

“…Although the ITA supplies only one-third of the blood supply to the parathyroids, few studies have reported increased rates of hypocalcemia with truncal ITA ligation. 7,26 Halsted's "capsular dissection" with ligation of the tertiary branches of ITA is a viable alternative to prevent complications. 45 Use of electrothermal bipolar vessel sealer (Ligasure) or ultrasonic devices (harmonic focus)may be helpful in reducing postoperative temporary hypocalcemia.…”