Better consenting for thyroidectomy: who has an increased risk of postoperative hypocalcaemia?

Hypocalcaemia is the most common complication following thyroidectomy. This study aimed to establish the factors associated with increased risk of hypocalcaemia on day 1 following thyroidectomy. All patients who underwent thyroidectomy under a single consultant during a 5-year period were included. A multivariate analysis was undertaken to ascertain which variables had the most effect on the risk of hypocalcaemia. A prognosis table was constructed to allow risk to be predicted for individual patients based on these factors. Included in the analysis were 210 procedures and 194 patients. Eighty-two percent of patients had no calcium derangement postoperatively. Fourteen point nine percent were categorised as early hypocalcaemia, 1 % had protracted hypocalcaemia and 2.1 % had permanent hypocalcaemia. For hemi-thyroidectomies 2.8 % had postoperative hypocalcaemia and 0.9 % had permanent hypocalcaemia. The multivariate analysis revealed total thyroidectomy (risk ratio 26.5, p < 0.0001), diabetes (risk ratio 4.8, p = 0.07) and thyrotoxicosis (risk ratio 3.1, p = 0.04) as statistically significant variables for early postoperative hypocalcaemia. Gender as an isolated factor did not reach significance but was included in the model. The p value for the model was p < 1 × 10-12. Total thyroidectomy increases risk of early hypocalcaemia when compared to hemithyroidectomy. Gender, diabetes and thyrotoxicosis were also been found to influence the risk. All of these factors are available pre-operatively and can therefore be used to predict a more specific risk for individual patients. It is hoped that this can lead to better informed consent, prevention and better resource allocation.