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.