Postoperative calcium requirements in 6,000 patients undergoing outpatient parathyroidectomy: easily avoiding symptomatic hypocalcemia

BACKGROUND: To determine the amount and duration of supplemental oral calcium for patients with varying clinical presentations discharged immediately after surgery for primary hyperparathyroidism.

STUDY DESIGN: A 4-year, prospective, single-institution study of 6,000 patients undergoing parathyroidectomy for primary hyperparathyroidism and discharged within 2.5 hours. Based on our previous studies, patients are started on a sliding scale of oral calcium determined by a number of preoperative measures (ie, serum calcium, body weight, osteoporosis) beginning 3 hours postoperation and decreasing to a maintenance dose by week 3. Patients reported all hypocalcemia symptoms daily for 2 weeks.

RESULTS: Seven parameters were found to have a substantial impact on the amount of calcium required to prevent symptomatic hypocalcemia: preoperative serum calcium >12 mg/dL, >13 mg/dL, and >13.5 mg/dL, bone density T score less than -3, morbid obesity, removal of >1 parathyroid, and manipulation/biopsy of all remaining glands (all p < 0.05). Each independent variable increased the daily calcium required by 315 mg/day. Using our scaled protocol, <8% of patients showed symptoms of hypocalcemia, nearly all of whom were successfully self-treated with additional oral calcium. Only 6 patients (0.1%) required a visit to the emergency room for IV calcium, all occurring on postoperative day 3 or later.

CONCLUSION: After outpatient parathyroidectomy, a specific calcium protocol has been verified that eliminates development of symptomatic hypocalcemia in >92% of patients, identifies patients at high risk for hypocalcemia, and allows self-medication with confidence in a predictable fashion for those patients in whom symptoms develop.