Do Intraoperative Total Serum and Ionized Calcium Levels, Like Intraoperative Intact PTH Levels, Correlate with Cure of Hyperparathyroidism?

Intraoperative parathyroid hormone (ioPTH) monitoring is useful in the operative management of hyperparathyroidism. Measurement of intraoperative total serum calcium (TSC) and ionized calcium (ICa) levels may be less expensive and more readily available methods of intraoperative guidance during neck dissection than ioPTH levels, the gold standard. We compared the accuracy of monitoring intraoperative TSC and ICa to that of ioPTH for predicting surgical cure during parathyroidectomy. Over a 10-month period, 47 parathyroidectomies were performed, during which ioPTH, TSC, and ICa were measured. Samples were obtained at the start of the operation and 5 and 10 minutes after gland removal. Data were compared and trends analyzed with respect to removal of abnormal parathyroid tissue as confirmed by pathology. The Wilcoxon signed rank test was used to determine if decreases in TSC and ICa were significant. The mean baseline ioPTH level (253 ± 247 pg/ml) dropped by 70% at 5 minutes after removal of the abnormal glands (68 ± 85 pg/ml) and by 83% at 10 minutes (32 ± 25 pg/ml). The mean baseline TSC level (10.1 ± 0.9 mg/dl) dropped by 4% at 5 minutes after removal of the abnormal glands (9.7 ± 0.8 mg/dl) and remained at 4% at 10 minutes (9.6 ± 0.7 mg/dl). The mean baseline ICa level (1.4 ± 0.1 mmol/dl) also dropped by 4% at 5 minutes after removal of the abnormal glands (1.3 ± 0.1 mmol/dl) and remained at 4% at 10 minutes (1.3 ± 0.1 mg/dl). ioPTH dropped by ≥ 50% in 39 patients (83%) at 5 minutes and in 46 patients (98%) at 10 minutes after gland resection. TSC decreased below baseline at 5 minutes and remained below baseline at 10 minutes in only 37 patients (79%). In the remaining 21% of patients, TSC decreased inconsistently, if at all, with respect to baseline at both the 5- and 10-minute time points. ICa decreased below baseline at 5 minutes and remained below baseline at 10 minutes in only 35 patients (77%). In the remaining 23% of patients, ICa, like TSC, changed inconsistently at 5 and 10 minutes after parathyroidectomy with respect to baseline levels. Decreases in TSC and ICa during parathyroidectomy, if present, are thus minimal. Unlike ioPTH levels, TSC and ICa levels do not consistently decrease at 5 and 10 minutes after gland resection. Although inexpensive and readily available, monitoring the intraoperative TSC and ICa is not clinically reliable for confirming removal of hyperfunctioning parathyroid glands.