Predictors of postoperative hypocalcemia occurring after a total thyroidectomy: results of prospective multicenter study

Background: Thyroid surgeries are among the most common operations performed in the world. Hypocalcemia following total thyroidectomy is a common complication that is sometimes difficult to correct. The aim of this study is to determine the risk factors for hypocalcemia following total thyroidectomy and their clinical value. Methods: From January 2015 through to April 2017, 400 patients were included in this prospective multicenter study. All patients underwent total thyroidectomy due to various thyroid diseases. The following risk factors were analyzed: pre-operative and post-operative biochemical blood parameters, clinical effects and factors related to surgery, the patient, and the disease. Results: Post-operative hypocalcemia developed in 257 patients (64.2%). Of them, 197 patients (76.7%) were diagnosed with asymptomatic hypocalcemia. Clinical symptoms were present in 60 of the 257 patients with hypocalcemia (23.3%). The statistically significant predictors of hypocalcemia were decreased calcium and ionized calcium pre-operatively (p < 0.001), parathyroid hormone on day one following surgery (p < 0.001), thyrotoxicosis < 10 years before surgery (odds ratio 1.65, 95% CI 1.01-2.70, p = 0.046), the number of parathyroid glands found during surgery (odds ratio 0.52, 95% CI 0.38-0.70, p < 0.001), ligation of the trunk of the left inferior thyroid artery (odds ratio 2.04, 95% CI 1.27-3.29, p = 0.003), ligation of the trunk of the right inferior thyroid artery (odds ratio 2.37, 95% CI 1.47-3.81, p < 0.001), and the number of transplanted parathyroid glands (odds ratio 1.87, 95% CI 1.12-2.97, p = 0.015). In the multivariate analysis, age (odds ratio 1.05, 95% CI 1.01-1.09, p = 0.029) and gender (odds ratio 5.94, 95% CI 1.13-31.26, p = 0.035) were statistically significant predictors. Conclusions: This study demonstrates that there is a number of different patient (gender, age, and duration of thyrotoxicosis < 10 years before surgery) and surgical (number of parathyroid glands found during surgery, decreased calcium and ionized calcium before surgery, parathyroid hormone on day one following surgery, and ligation of the trunk of the left and right inferior thyroid artery) risk factors predictive of hypocalcemia following total thyroidectomy. Optimization of the surgical technique could possibly prevent the occurrence of hypocalcemia after total thyroidectomy in some cases; in other cases, identification of known risk factors post-operatively could permit early detection and effective treatment of these patients.