B. C. James1, M. White1, S. Nagar1, C. Nocon2, E. Kaplan1, P. Angelos1, R. H. Grogan1 1University Of Chicago,Division Of Endocrine Surgery/Department Of Surgery/Pritzker School Of Medicine,Chicago, IL, USA 2University Of Chicago,Division Of Otolaryngology/Department Of Surgery/Pritzker School Of Medicine,Chicago, IL, USA
Introduction:
One of the major morbidities associated with thyroidectomy is hypocalcemia. With the increasing push towards outpatient surgery, we sought to determine whether a single serum calcium or PTH level drawn after total thyroidectomy combined with clinical factors could predict the development of symptomatic hypocalcemia.
Methods:
This single institution, prospective cohort study evaluated 197 patients undergoing total thyroidectomy with and without central lymph node dissection (LNDx) over a 17-month period. Serum calcium and parathyroid hormone (PTH) levels were measured one hour after surgery and again on postoperative day 1 (POD1). Serum levels were grouped into PTH ≤ 10pg/dL or >10 and calcium levels ≤ 8mg/dL or >8. Using Student’s t-test with significance defined as p<0.05 and linear regression testing, univariate and multivariate analyses were performed to determine which serum levels and clinical factors best predicted symptomatic hypocalcemia.
Results:
197 patients underwent total thyroidectomy, 103 (52%) for malignancy and 94 (48%) for benign disease. Of these, 29 (15%) patients underwent LNDx and 29 (15%) patients underwent parathyroid autotransplantation. Thirty-four (17%) patients had a 1-hour postoperative PTH of 10 or less while 31 (16%) patients had a POD1 PTH of 10 or less. Sixteen (8%) patients had a 1-hour postoperative calcium of 8 or less while 83 (42%) patients had a POD1 calcium of 8 or less. In total, 9 (4.5%) patients developed symptomatic hypocalcemia. When we evaluated for clinical factors, five of these nine patients had undergone LNDx and 4 required autotransplantation. Four of these 9 symptomatic patients had a POD1 PTH of 10 or less and also had a 1-hour postoperative PTH of 10 or less. Thus, a PTH of 10 or less 1-hour postoperatively or on POD1 was 44% sensitive (CI 13.97-78.60) in predicting symptomatic hypocalcemia. Linear regression analysis demonstrated a strong correlation (r=0.826) between 1-hour postoperative and POD1 PTH levels. Comparing 1-hour postoperative calcium and POD1 calcium, neither value correlated with the development of symptomatic hypocalcemia (p>0.21). On multivariate analysis, parathyroid autotransplantation did not increase the sensitivity of 1-hour postoperative PTH. However, when combining a 1-hour postoperative PTH level of ≤ 10 with LNDx, the sensitivity increased to 67% with a specificity of 74%.
Conclusion:
We found that the 1-hour postoperative PTH was equivalent to the POD1 PTH in predicting the development of hypocalcemic symptoms. Considering the advantages of having an equally predictive PTH level 1-hour postoperatively, we believe the 1-hour postoperative PTH level is the best test to use. When combining this value with patients who underwent LNDx, few patients who develop hypocalcemic symptoms are missed. We therefore recommend all patients with a PTH ≤ 10 or undergoing LNDx be placed on calcium supplementation before discharge.