Factors predicting hypocalcemia after total thyroidectomy - A retrospective cohort analysis

Abstract

Background: Hypocalcemia after total thyroidectomy is the most frequent complication resulting in prolongation of hospitalisation. Therefore we aimed to analyse clinical risk factors predictive for hypocalcemia and its long term persistence after total thyroidectomy.

Methods: Retrospective analysis of patients undergoing total thyroidectomy from 2005 until 2013. Outcome measures were initial postoperative hypocalcemia defined as serum calcium below 2.0 mmol/l after total thyroidectomy within 48 h and persistent hypocalcemia defined as serum calcium below 2.0 mmol/l above six months and/or the need for additional calcium and vitamin D supplementation.

Results: Initial postoperative hypocalcemia was present in 160 of 702 patients (22.8%) with 91 patients (13%) developing symptoms. 48 patients (6.8%) had a persistent hypocalcemia above six months. Patients with an initial symptomatic postoperative hypocalcemia showed significantly more often a persistent hypocalcemia compared to asymptomatic patients with biochemical hypocalcemia (38 patients (41.8%) vs. 10 patients (14.5%), p < 0,001). In the binary logistic regression analysis, female gender (OR 2.4; CI95% 1.5-3.8), prolonged surgery time >189 min (OR 1.8; CI95% 1.2-2.6) and parathyroid reimplantation (OR 2.4; CI95% 1.2-4.7) were associated with initial hypocalcemia while only initial symptomatic hypocalcaemia was shown to be independently associated with persistent hypocalcemia (OR 40.9; CI95% 18.5-90.4).

Conclusion: Prolonged surgery time seems to correlate with initial postoperative hypocalcemia independently of the underlying disease and surgical expertise but does not affect the persistence of hypocalcemia. Initial symptomatic postoperative hypocalcemia after total thyroidectomy is associated with a high rate of persistent hypocalcemia.

Keywords: Hypocalcemia; Prolonged surgery time; Total thyroidectomy.