Risk factors for postoperative hypocalcemia after surgery for primary hyperparathyroidism.

HYPOTHESIS A variety of clinical and biochemical variables may be associated with hypocalcemia after surgery for parathyroid adenoma. DESIGN A prospective study of patients who underwent surgery for solitary parathyroid adenoma. SETTING A university hospital department of surgery. PATIENTS Eighty-six consecutive patients who underwent surgery for solitary parathyroid adenoma. INTERVENTION Parathyroidectomy according to the principles of unilateral neck exploration. MAIN OUTCOME MEASURES Clinical and biochemical risk factors for early (< or =4 days after surgery) and late (1 year after surgery) postoperative symptomatic and biochemical hypocalcemia. RESULTS Twenty-two patients developed early symptomatic hypocalcemia. The difference in total serum calcium levels between patients, with and without early symptomatic hypocalcemia, was evident on the third and fourth postoperative days. Serum level of osteocalcin greater than 6.0 microg/L, bilateral neck exploration, and history of cardiovascular disease were risk factors for symptomatic hypocalcemia (odds ratios [95% confidence intervals]: 4.4 [1.4-14.1], 3.8 [1.3-11.6], and 0.1 [0.02-0.60], respectively). Patients with up to 1 risk factor had a possibility of only 7% to develop early symptomatic hypocalcemia. One year after surgery, 16 patients had low levels of total serum calcium (late biochemical hypocalcemia) and were asymptomatic. Preoperative intermittent hypercalcemia was associated with an increased risk for late biochemical hypocalcemia (odds ratio, 3.9; 95% confidence interval, 1.0-16.3). CONCLUSIONS Clinical and biochemical risk factors for early and late postoperative hypocalcemia in patients who underwent surgery for solitary parathyroid adenoma were found. A clinically useful prognostic index for early symptomatic hypocalcemia was constructed using these risk factors.