Comparison of serum calcium change following thyroid and nonthyroid neck surgery

OBJECTIVE: Compare serum calcium changes following thyroid and nonthyroid/parathyroid neck surgery. STUDY DESIGN: Controlled historic cohort study of 190 patients undergoing total thyroidectomy (TT, n = 97), completion thyroidectomy (CT, n = 27), and lateral neck dissection (ND, n = 66). RESULTS: Each group experienced significant corrected serum calcium drop pre-op to POD #1 (mean change (mg/dL) TT = 0.97, CT = 0.79, ND = 0.46; all P < 0.001) with significantly greater drop in TT and CT (P < 0.0001). TT and ND had significantly greater calcium drop from pre-op to PACU than CT (0.54, 0.43, 0.15; P = 0.04). TT and CT experienced significantly greater calcium drop from PACU to POD #1 than ND (0.45, 0.53, 0.05; P < 0.0001). No significant difference in hypocalcemia rate between TT and CT. CONCLUSIONS: Perioperative calcium drop in nonthyroid neck surgery is likely hemodilutional, occurring intraoperatively, whereas in thyroid surgery it likely results from both hemodilution and parathyroid dysfunction with the latter manifesting after PACU. Postoperative calcium monitoring should be similar following total and completion thyroidectomy due to similar rates of hypocalcemia and mean calcium drops. EBM rating: B-3b.