Risk Factors for Hypocalcemia Following Total Thyroidectomy: A Retrospective Cohort Study
DOI:
https://doi.org/10.54361/LJMR.20.2.79Keywords:
Hypocalcaemia, Hypoparathyroidism, Thyroidectomy, Thyroid cancer, Parathyroid glandsAbstract
Background. Hypocalcaemia is the most frequent complication of total thyroidectomy. Reported incidences vary widely, from 15% to more than 60% for transient hypocalcaemia and from 0.2% to 10% for permanent hypoparathyroidism, and the risk factors that drive this variation remain incompletely defined. Objectives. To determine the incidence of post-operative hypocalcaemia after total thyroidectomy at a Libyan tertiary teaching hospital and to identify the clinical, operative and pathological factors associated with its development. Materials and Methods. We conducted a retrospective cohort study of consecutive patients aged 16 years or older who underwent total thyroidectomy at Tobruk Medical Center between January 2016 and December 2020. Pre-operative, intra-operative and tumour-related variables were abstracted from electronic medical records and histopathology reports. Hypocalcaemia was defined as an albumin-corrected total serum calcium below 8.0 mg/dL or an ionised calcium below 4.0 mg/dL recorded at any point during the index admission. Groups were compared using the chi-squared or Fisher exact test for categorical variables and the Student t-test or Mann-Whitney U test for continuous variables, followed by univariable and multivariable logistic regression. Results. Of 337 patients who underwent total thyroidectomy during the study period, 290 had complete post-operative calcium follow-up and constituted the analysis cohort. Median age was 47 years; 223 patients (76.9%) were women. Thyroid carcinoma was the operative indication in 219 patients (75.5%). Post-operative hypocalcaemia occurred in 37 patients (12.8%). On univariable analysis, intra-operative parathyroid gland injury (OR 2.49, 95% CI 1.11-5.59), drain placement (OR 2.40, 95% CI 1.19-4.87), concomitant lymph node dissection (OR 2.45, 95% CI 1.20-4.90) and operative time exceeding 2.5 hours (OR 2.00, 95% CI 1.03-4.19) were each associated with hypocalcaemia. In the multivariable model, only parathyroid gland injury remained independently associated with the outcome (adjusted OR 3.68, 95% CI 1.65-8.21; p = 0.001). No patient receiving pre-operative levothyroxine developed hypocalcaemia (0 of 34); because this zero cell produced complete separation, the association is reported descriptively rather than modelled. Conclusions. Intra-operative parathyroid gland injury was the only independent risk factor for hypocalcaemia after total thyroidectomy in this cohort. Because such injury is recognised by the operating surgeon at the time of the procedure, it identifies intra-operatively a subgroup of patients who may benefit from closer post-operative calcium monitoring and earlier supplementation.
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