Massachusetts Chapter of the American College of Surgeons

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Impact of Obesity on Risk of Hypocalcemia after Total Thyroidectomy: Targeted NSQIP Analysis of 16,277 Patients
Stefanie Soelling, David A. Mahvi, Gerard Doherty, Matthew Nehs, Nancy Cho
Brigham and Women's Hospital, Boston, MA

Background: Hypocalcemia following total thyroidectomy (TT) is common due to both postoperative parathyroid dysfunction and vitamin D deficiency. Given the association between obesity and vitamin D deficiency, we sought to correlate BMI with hypocalcemia after TT.
Methods: The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) thyroidectomy-targeted database was utilized for patients undergoing TT between 2016-2020. Univariable and multivariable regression were used to identify factors associated with hypocalcemia at discharge and 30 days, and hypocalcemic events (emergent evaluation in clinic/emergency department, IV calcium supplementation, or readmission for hypocalcemia).
Results: 16,277 TT were performed with available BMI data. 21.7% of patients had normal BMI (18.5-24.9 kg/m2), 29.6% were overweight (25-29.9 kg/m2), and 47.7% were obese (?30 kg/m2). Patients with BMI > 25 had decreased risk of hypocalcemia at discharge (5.8% vs 8.2%, OR 0.69, p<0.001, 30 days (8.1% vs 10.4%, OR 0.76, p<0.001), and hypocalcemic events (5.5% vs 6.4%, OR 0.84, p=0.029) compared to normal BMI patients. On multivariable analysis for patients with BMI < 25, younger age was a risk factor for hypocalcemia at discharge, 30 days, and hypocalcemic events (p<0.05 for all). Additional risk factors in normal BMI group for hypocalcemia at 30 days included parathyroid autotransplant and neck dissection (p<0.05) and recurrent laryngeal nerve injury for hypocalcemic events (p=0.007).
Conclusion: Younger patients with BMI < 25 are at increased risk for hypocalcemia and hypocalcemic events after TT. These patients may benefit from preoperative counseling and increased Calcium/vitamin D supplementation to reduce prolonged hospitalization and mitigate morbidity.

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