An Algorithm Informed by the Parathyroid Hormone Level Reduces Hypocalcemic Complications of Thyroidectomy

Measurement of the parathyroid hormone (PTH) level following total thyroidectomy (TTx) may allow prediction of postoperative hypocalcemia. We present an algorithmic method of managing hypocalcemia pre-emptively, based on the PTH level 1 h after operation. We examined 423 consecutive patients undergoing TTx at a single institution. A subset of patients were managed using an algorithm involving routine postoperative oral calcium administration and the early addition of oral calcitriol in patients with a low 1-h postoperative PTH level. Algorithm patients were compared to a concurrent, conventionally managed group. Outcomes measured included serum calcium levels, symptoms of hypocalcemia, postoperative complications, and receipt of intravenous (IV) calcium. The algorithm was applied in 135 patients, and 288 patients were managed conventionally. Critically low calcium levels (total calcium < 7.5 mg/dl [1.88 mmol/l] or ionized calcium < 0.94 mmol/l) were less common in algorithm patients (10.6% vs. 25.3%; p < 0.005). Much of this difference was attributable to the protective impact of the algorithm on patients undergoing TTx for cancer, 30% of whom developed critically low calcium levels when managed conventionally. Among patients requiring IV calcium, algorithm patients received fewer doses (1.29 vs. 1.86; p < 0.05). Low 1-h PTH levels were found in 21% (28/133) of algorithm patients, but these did not correlate with low calcium levels, suggesting that the algorithm compensated adequately for temporary hypoparathyroidism. No patients developed hypercalcemia. An algorithmic approach incorporating early postoperative PTH levels and routine administration of oral calcium reduces the risk of severe hypocalcemia after total thyroidectomy.