Early Prediction of Hypocalcemia Demanding Treatment after Total Thyroidectomy

ABSTRACT

PURPOSE: The clinical manifestation of hypocalcemia is usually delayed until 48 to 72 hours after a thyroidectomy. A reliable predictor of postoperative hypocalcemia demanding treatment will shorten the hospital stay. This study prospectively evaluated the clinical and biochemical characteristics of patients who had hypocalcemia demanding treatment along with their predictive values. METHODS: The data was collected from 44 patients who underwent a total thyroidectomy at Chungbuk National University hospital from September 2003 to July 2004. There were 38 females and 6 males. Thirty-one patients were diagnosed with thyroid carcinoma. The serum calcium, phosphorous, ionized calcium, and PTH levels were measured at 6, 12, 24, and 48 hours after surgery. The clinical and biochemical characteristics of the patients who demanded treatment (Treated) were compared with those of the other patients (Control). Statistical analysis was carried out using a student t-test and a chi2 test. RESULTS: Among the 44 patients, 11 patients (25.0%) required calcium supplementation. The clinical characteristics except for age were not different between the two groups. The serum calcium, calcium ion, and PTH levels were significantly lower in the treated group from as early as 6 hours after surgery. In order to predict hypocalcemia demanding treatment with both a sensitivity and a specificity of approximately 90%, the biochemical cut-off value would be 15 pg/ml PTH at 6 hours, 4.0 mg/dl of a minimal ionized calcium within 24 hours, and 7.9 mg/dl calcium at 48 hours after a total thyroidectomy. CONCLUSION: Hypocalcemia demanding treatment can be predicted early and reliably after a total thyroidectomy by measuring the postoperative changes in the serum calcium, ionized calcium, and PTH levels.