Evaluación de viabilidad de las glándulas paratiroides mediante angiografía con verde de indocianina para la predicción de hipocalcemia tras tiroidectomía total

Abstract

Introduction: Hypocalcemia is one of the commonest complications after total thyroidectomy. Although not fully elucidated, the proposed underlying mechanism for hypocalcemia after total thyroidectomy is related to the development of hypoparathyroidism. It might result from intraoperative damage to the parathyroid glands (PGs) due to mechanical or thermal trauma, devascularization, venous obstruction or inadvertent removal. Recent studies have suggested that the evaluation of PGs viability by means indocyanine green (ICG) angiography may be useful for predicting postoperative parathyroid function and hypocalcemia. However, these studies did not assess the viability of all PGs for predict the development of postoperative hypocalcemia or the residual parathyroid function status. Objectives: Given that postoperative calcium level depends on circulating parathyroid hormone (PTH) levels, and these could be attributed directly to the residual PGs functionality, the main aim of this study was to evaluate the ability to predict postoperative hypocalcemia considering the viability status of all PGs. For this application, a simple quantitative scoring system based on ICG angiography findings of all PGs was proposed: the global viability score (GVS). Moreover, the correlation between the GVS and the postoperative parathyroid function and the degree of intra- and interobserver concordance in the assessment of ICG angiography-based viability were evaluated. Methods: Thirty-nine consecutive patients underwent total thyroidectomy for multinodular goiter were included. All procedures were performed by experienced consultant&apos;s surgeons of the Endocrine Surgery Unit of participant institutions. Once the thyroid gland had been removed, ICG angiography of the PGs identified was performed using the laparoscopic PinPoint camera (Nodadaq, Ontario, Canada). Three independent observers rated the viability of each PG assessing the previously acquired ICG-enhanced fluorescence imaging (from 0 point if it were non-vascularized to 2 points if it were well vascularized). For each patient, the GVS was calculated adding the individual viability value of the four PGs. Postoperative hypocalcemia was defined as a albumin-corrected total serum calcium concentration < 8 mg/dl at 24 hours after surgery. Serum PTH was determined preoperative and at various postoperative times. Discrimination, correlation and concordance analyses was performed. Results: In 32 of the 39 patients the four PGs were identified. There were 41 (32%) PGs with 2 points (well vascularized) and 32 (25%) with 0 point (non-vascularized). Patients with postoperative hypocalcemia (n=6, 19%) had a lower GVS (2.5 [1.8 - 3.3] vs. 4.0 [3.0 - 6.0]; p = 0.003). The GVS score showed a good ability for predicting postoperative hypocalcemia (AUC = 0.875 (0.710 - 0.965); p = 0.001). The optimal GVS score cut-off value was ? 3. Using this cut-off value, the sensitivity, specificity, positive predictive value and negative predictive value for predicting postoperative hypocalcemia were 83% (36 - 100), 73% (52 - 88), 42% (15 - 72) and 95% (75 - 100); respectively. The GVS showed a moderate positive correlation with the postoperative absolute PTH levels (Spearman&apos;s rho = 0.572; p = 0.001) and a strong negative correlation with the postoperative relative PTH drop (Spearman&apos;s rho = -0.701; p < 0.001). The intra- and interobserver concordance were good/almost perfect and moderate/good, respectively. Conclusions: The GVS predicts postoperative hypocalcemia and correlates with postoperative parathyroid function in patients undergoing total thyroidectomy for multinodular goiter.