The role of intraoperative rapid parathyroid hormone monitoring for predicting thyroidectomy-related hypocalcemia

Objective: To determine if the intraoperative rapid parathyroid hormone (PTH) assay can be used to accurately predict postoperative calcium levels following total or completion thyroidectomy. Design: A prospective study. Setting: Tertiary care referral center. Patients: One hundred four patients following a total or completion thyroidectomy. Intervention: Intraoperative rapid plasma PTH levels were determined for patients undergoing a total or completion thyroidectomy. Main Outcome Measures: Parathyroid hormone levels were recorded after the induction of anesthesia, before excision, and 5, 10, and 20 minutes after thyroidectomy. Postoperative calcium levels were monitored every 6 hours until hospital discharge. Intraoperative PTH levels were correlated with postoperative calcium levels and clinical symptoms of hypocalcemia. Results: Twenty-two patients (21.2%) required short-term postoperative calcium supplementation, and 2 (1.9%) required long-term calcium replacement. There was a statistically significant difference between those patients requiring calcium replacement and those who did not require calcium supplementation, for postoperative total calcium level (7.2 vs 8.1 mg/dL [1.8 vs 2.0 mmol/L]; P<.001) and ionized calcium level (3.76 vs 4.36 mg/dL [0.94 vs 1.09 mmol/L]; P<.001). In addition, the PTH changes from baseline demonstrated statistically significant differences at 5, 10, and 20 minutes after the excision between the 2 groups (P<.005). In those patients requiring calcium supplementation, 14 (64%) of 22 demonstrated a change in PTH level at 20 minutes of greater than 75% from baseline, and in those patients who did not require postoperative calcium supplementation, 61 (74%) of 82 demonstrated a change in PTH level of less than 75% from baseline (P<.005). Conclusion: Intraoperative PTH monitoring may be a useful tool in identifying patients who will not require postoperative calcium supplementation following total or completion thyroidectomy.