Rate of drop in serum calcium as a predictor of hypocalcemic symptoms post total thyroidectomy

The rate of drop in serum calcium post total thyroidectomy is a predictor of hypocalcemic symptoms in adults, after adjusting for other significant covariates.

Test the hypothesis that rate of drop in calcium is a significant and independent predictor of post-operative hypocalcemic symptoms post total thyroidectomy.

A retrospective chart review (electronic and hard copy) for 429 patients who underwent total thyroidectomy from January 2011 to December 2016. We collected information on demographics, clinical characteristics, information on surgical intervention, histopathology reports, clinical course, biochemistries, treatments and discharge instructions.

Sixty-one patients (14%) developed post-operative hypocalcemic symptoms. The rate of calcium drop, younger age, female gender, and lower body mass index, and the presence of parathyroid tissue in resected specimen all correlated significantly with the development of symptoms. The rate of drop in serum calcium and the post-operative serum calcium level remained the only significant predictors of symptom development, after adjustment for other significant co-variates. Using a receiver operating characteristics curve, a cutoff rate of calcium drop > 0.083 mg/dl/h, that is 1 mg/dl over 12 h, has a sensitivity of 71% and specificity of 73% for detecting hypocalcemic symptoms.

The rate of drop of serum calcium post total thyroidectomy significantly and independently correlated with the development of hypocalcemic symptoms. Patients with a rate of drop < 1 mg/dl/12 h may be considered for earlier discharge and less aggressive management peri-operatively.