Purpose: Serum calcium has been suggested to be a surrogate marker for intraoperative monitoring during a parathyroidectomy (PTX) for primary hyperparathyroidism (pHPT). The objective of the present prospective study was to investigate whether serum calcium can be used as an alternative for parathyroid hormone intraoperative monitoring.
Methods: Intact parathyroid hormone (iPTH), total and ionized serum calcium, total protein (tP), and pH were monitored in parallel in 25 patients during a successful directed PTX for pHPT.
Results: All patients had at least a 50% decrease of iPTH 10 min after PTX. Simultaneously measured total serum calcium (tCa) and ionized serum calcium (iCa) did not correlate with iPTH or pH. However, tCa and iCa levels correlated with changes in tP (r = 0.859; P < 0.001; r = 0.483; P = 0.014). In addition, intraoperative iCa changes correlated with preoperative iCa levels (r = -0.475, P = 0.016). A linear regression analysis for parameters potentially influencing intraoperative tCa and iCa dynamics changes identified tP changes as the only parameter influencing tCa and iCa changes (P < 0.001).
Conclusion: Individual short-term intraoperative changes of tCa or iCa are not predictive for successful PTX, as they more likely reflect changes in intraoperative fluid management rather than decreased iPTH.