Serum calcium slope predicts hypocalcaemia following thyroid surgery

Hypocalcaemia is the single commonest complication of thyroid surgery. Typically, serial calcium levels are performed post-operatively in order to detect hypocalcaemia, often requiring at least a 48-h stay. Our practice is to measure serum corrected calcium pre-operatively, 6 h post-operatively and 24 h post-operatively. Patients are discharged if they have a normal serum calcium value at 24 h.

We performed a retrospective review to determine if the calcium slope from pre-operatively to 6 h post-operatively predicts serum calcium levels at 24 h, thus allowing early discharge.

Fifty-two patients who underwent total or subtotal thyroidectomies were studied. Hypocalcaemia developed in 19 patients within 24 h of surgery (serum adjusted calcium less than 2.15 mmol/dL) within 24 h of surgery. There were no significant differences between the hypocalcaemic and normocalcaemic groups with respect to Graves' disease (p=0.17), total thyroidectomy (p=0.39), number of parathyroids identified (p=0.66), or parathyroid autotransplantation (p=0.29). The serum calcium slope from baseline to 6 h post-operatively correlated with serum calcium values at 24 h (p=0.008).

Serum calcium slope may be useful in identifying patients suitable for early discharge following thyroid surgery.