Identification of patients at high risk for hypocalcemia after total thyroidectomy

Hypocalcemia is a major post-operative complication of total thyroidectomy, causing severe symptoms and increasing hospitalization time. The primary cause is secondary hypo-parathyroidism following damage to, or devascularisation of, one or more parathyroid glands during surgery. Aim of the study was to develop a simple and reliable method for predicting post-operative hypocalcemia in total thyroidectomy patients. A retrospective analysis was made of immediate pre-operative and early post-operative calcium levels in 100 patients. It was found that a marked decrease in blood calcium, immediately after surgery, was a sensitive predictor of hypocalcemia. In a subsequent prospective series of 67 patients, the efficacy was assessed of early administration of calcium plus Vitamin D in reducing symptomatic hypocalcemia in patients in whom the difference (Δ) between pre- and post-operative blood calcium was ≥ 1.1 mg/dl. This treatment was part of a protocol in which normo-calcemic patients were discharged immediately after drainage removal (third post-operative day). In the retrospective series, 84% of patients who developed hypocalcemia had Δ ≥ 1.1 and 54% of patients who did not develop hypocalcemia had Δ < 1.1 (p < 0.0001). Mean duration of hospitalization was 6.2 days. In the prospective series, 76% of patients who developed hypocalcemia had Δ ≥ 1.1 mg/dl; of the patients who did not develop hypocalcemia 75% had Δ < 1.1 mg/dl (p = 0.0013); mean hospitalization was 4.7 days (p < 0.0001). Use of the 1.1 mg/dl cut-off for deciding whether to start early prophylaxis allowed most patients to avoid symptomatic hypocalcemia (and the associated anxiety), while permitting a significantly reduced hospital stay, resulting in lower hospitalization costs.