Incidence and Risk Factors for Post-thyroidectomy Hypocalcemia

Objectives: This study aimed to determine the incidence and risk factors for post-thyroidectomy hypocalcemia.

Methodology: This was a retrospective cohort study of 242 patients who underwent total or completion thyroidectomy from 2011-2014 at St. Luke’s Medical Center, Quezon City, Philippines. The overall and specific incidences of hypocalcemia were determined. Patient- and surgery-related factors were assessed and hypocalcemic events described.

Results: Overall incidence of hypocalcemia is 45.9% distributed to: symptomatic (33.9%), symptomatic + biochemical (10.7%) and biochemical (1.2%). Mean post-operative iCa was lower in hypocalcemic (1.04±0.08 vs 1.11±0.05 mmol/L, p=<0.001). Other patient-related factors were not different (age, sex, thyroid disease and thyroid gland weight). Among surgery-related factors, presence of concomitant complication of thyroidectomy (hoarseness and/or hematoma) was a significant risk factor [27.02% vs. 9.92%; p=0.002; OR 3.47 (95%CI: 1.72, 7.39)]. Others were not different: thyroidectomy [total vs completion]; neck dissection; surgery duration (hours); surgeon [consultant vs. trainee], and inadvertent parathyroidectomy. Manifestations occurred 19.84±18.65 hours post-operatively and these were: Chvostek’s (67.6%), acral paresthesia (64.8%), perioral numbness (37.0%), carpopedal spasm (13.9%), Trousseau’s (2.8%) and cramps (0.9%).

Conclusion: In this study, hoarseness and/or hematoma, if present, are risk factors for post-thyroidectomy hypocalcemia. Closer monitoring of these patients for hypocalcemia may be necessary.