Utility of intraoperative parathyroid hormone measurement in predicting postparathyroidectomy hypocalcemia.

OBJECTIVE

To evaluate the role of a standardized intraoperative parathyroid hormone (PTH) assay in predicting postoperative hypocalcemia following parathyroidectomy for primary hyperparathyroidism.

STUDY

DESIGN

Prospective series of 66 patients undergoing unilateral or bilateral parathyroidectomy between January 2004 and June 2005.

SETTING

Tertiary care centre in Vancouver, British Columbia.

METHODS

Preoperatively, ionized calcium and PTH levels were recorded. A standardized intraoperative PTH assay was used to measure PTH levels on all patients at the following times: just prior to initial incision (Ti), just prior to adenoma excision (T0), and 5 and 10 minutes after excision (T5 and T10, respectively). Calcium levels were drawn at 8 and 16 hours postoperatively. Clinically significant hypocalcemia was defined as a symptomatic patient or a serum ionized calcium < or = 1.1 mmol/L.

MAIN OUTCOME MEASURES: Postoperative hypocalcemia following parathyroidectomy.

RESULTS

The incidence of postoperative hypocalcemia was 12% (8 of 66). There was no significant correlation between postoperative hypocalcemia and any of the evaluated factors, including intraoperative values of PTH (all p > .05). The percentage change between ioPTH at Ti and at T10 was, however, significantly associated with the development of postoperative hypocalcemia (odds ratio = 3.47 for a 10% decline, p = .03).

CONCLUSIONS

Percentage change in intraoperative PTH levels between the initial incision and at 10 minutes post-parathyroid adenoma excision is a significant predictor of postoperative hypocalcemia following parathyroidectomy for primary hyperparathyroidism.