Diagnostic value of intraoperative parathyroid hormone decline in prediction of hypocalcemia after total thyroidectomy

Background and objective: Transient or definitive hypocalcemia is one of the most important complications following total thyroidectomy. Monitoring of serum calcium levels or calcium replacement in all patients are methods commonly used to avoid this problem. Our objective was to validate the intraoperative parathormone assay (PTH) as a predictive tool in these situations. Patients and method: We conducted a prospective study of 46 patients undergoing total thyroidectomy. PTH levels were obtained during the anesthetic induction, 10min after the procedure and 24h after surgery. Calcium levels were obtained 24 and 48 h after surgery. The predictive value of postoperatory levels of PTH and its decline respect the preoperatory levels for prediction of hypocalcemia was measured. Hypocalcemia was defined as an ionized calcium < 4mg/dl (< 1 mmol/1). Results: Of 46 patients, 13 (28.3%) developed hypocalcemia. Isolated postoperative PTH level was a poor predictor of hypocalcemia. Nevertheless, when the gradient between preoperative and postoperative levels of PTH was considered, the rate of the decline became a good predictor of hypocalcemia, with 85-90% being the most accurate cut-off point. Conclusions: The decline of PTH in the immediate postoperative period of patients undergoing total thyroidectomy is a reliable test for predicting hypocalcemia. (C) 2008 Elsevier Espana, S.L. All rights reserved.