Predictive factors for early postoperative hypocalcemia after surgery for primary hyperparathyroidism

The purpose of this study was to identify patients at risk for hypocalcemia after parathyroid surgery. The charts of 99 patients who underwent parathyroid surgery over a 2-year period using a rapid intraoperative parathyroid hormone (IOPTH) assay were retrospectively reviewed. Data for patient demographics, preoperative parathyroid hormone and calcium levels, IOPTH levels, and postoperative calcium levels were reviewed, and trends were analyzed for patients who had postoperative hypocalcemia. Of the 99 patients, 91 had one gland excised and 8 had two glands excised. Preoperative calcium levels ranged from 8.9 to 15.6 mg/dL. Sixty-seven of the patients had a >50% drop in IOPTH at 5 minutes, and 82 had a >50% drop in IOPTH by 10 minutes. Twelve patients had early hypocalcemia. Parathyroid weight and surgery type were not significant factors in predicting postoperative hypocalcemia. A drop of >80% in IOPTH at 10 minutes was a significant factor for postoperative hypocalcemia (P = 0.02). In addition, having normal or only minimally elevated preoperative calcium was an independent risk factor for postoperative hypocalcemia (P = 0.05). Our study has shown that postoperative calcium supplementation and in-hospital monitoring should be considered in patients with a preoperative calcium level in the normal range and with an IOPTH that has dropped by >80%.