Evaluation of ten years thyroidectomy results

Objective: The purpose of this study is to evaluate patients who underwent thyroidectomy in terms of complications, to determine the role of parathyroid hormone and serum calcium level measurements for prediction of hypocalcemia after thyroidectomy, to investigate the sensitivity and specificity values of intraoperative nerve monitoring for prediction of postoperative vocal cord paralysis after thyroidectomy and the correlation between the result of fine-needle aspiration biopsy and the final pathology result. Methods: 739 consecutive patients undergoing total, completion or hemithyroidectomy between October 2009 and December 2019 were included in the study. Demographic data (age, gender) of the patients, preoperative findings (reasons for revision surgery, presence of preoperative vocal cord paralysis, retrosternal extension and thyroid antibodies), postoperative complications such as vocal cord paralysis, hypocalcemia, hematoma, chylous fistula, seroma, wound site infection and duration of these complications, characteristics of surgery ((type of surgery, the experience of the primary surgeon, presence of neck dissection, whether a drain was placed, whether parathyroid autotransplantation was performed) and pathological examination (fine needle aspiration biopsy result, weight of thyroidectomy material, presence of parathyroid gland in the specimen, benign or malign pathology, T stage for malignant pathologies, presence of thyroiditis pathology) were examined. In addition, postoperative calcium and parathyroid hormone values and electromyography responses of recurrent laryngeal nerves before and after dissection obtained by performing intraoperative nerve monitoring were evaluated. Patients having at least one postoperative serum calcium level below 8.0 mg/dL were determined as hypocalcemic. Hypocalcemia more than 12 months was defined as permanent hypocalcemia. A response with an amplitude lower than 100 mV from 1 milliampere stimulus given to the RLS during the operation was considered as loss of signal. Vocal cord paralysis more than 12 months was defined as permanent vocal cord paralysis. Results: It was determined that 70 (9.5%) of 739 patients developed postoperative hypocalcemia. 54 (7.3%) patients had transient hypocalcemia, while 16 (2.2%) patients had permanent hypocalcemia. There was no statistically significant difference between hypocalcemic and normocalcemic patients in terms of age, gender, Graves disease, malignant pathology, and parathyroid gland autoimplantation (p>0.05). There was a statistically significant correlation between previous thyroid surgery history, retrosternal extension, incidental parathyroidectomy, increased thyroid gland weight, T3 and T4 tumor stage, completion thyroidectomy, central and lateral neck dissection, presence of drain in the post-operative cavity with the development of hypocalcemia (p<0.05). The surgeries performed by instructors of our university were also detected to be correlated with postoperative hypocalcemia development (p<0.05). In terms of the development of permanent hypocalcemia, history of thyroid surgery, retrosternal extension, tumor stage T3 and T4, completion thyroidectomy, central and lateral neck dissection, and presence of drain in the postoperative cavity were found to constitute high-risk groups with a statistically significant difference (p <0.05). Parathyroid concentration of 9.85 pg/mL measured at 24 hour after surgery had a 80.0% sensitivity and 71.1% specificity; and calcium concentration of 8.46 mg/dL measured at 24 hour after surgery had a 75.7% sensitivity and 86.3% specificity for predicting postoperative hypocalcemia. 61 patients had transient vocal cord paralysis and five patients had permanent vocal cord paralysis following thyroidectomy surgery. Vocal cord paralysis was detected in 67 of 1300 nerve at risk in total. Transient and permanent vocal cord paralysis rates in patients was 8.3% and 0.7% respectively. There was a statistically significant correlation between revision surgery, bilateral central neck dissection, more extensive surgery and the presence of drain in the postoperative cavity with the occurrence of postoperative vocal cord paralysis. Intraoperative nerve monitoring predicted postoperative vocal cord paralysis with 67.2% sensitivity, 98.2% specificity, 64.3% positive prediction, 98.2% negative predictive value when the threshold value for the responses received from recurrent laryngeal nerve at the end of the operation was accepted as 100 mV. The postoperative hematoma and seroma development rate was 2.2% and 3.7% respectively. The wound infection rate was determined to be 0.01%, while the chylous fistula development rate was 0.5%. It was determined that male gender, retrosternal extension, lateral neck dissection, presence of drain in the postoperative cavity and instructor's surgeries were high-risk groups in terms of hematoma development. In terms of seroma development, older cases were found to have a higher risk with a statistically significant difference. In our study, 33 (7.1%) patients Bethesda I, 104 (22.3%) patients Bethesda II, 37 (7.9%) patients Bethesda III, 35 (7.5%) patients Bethesda IV, 208 (44.5%) ) patient Bethesda V, 50 (10.7%) patients had Bethesda VI fine needle aspiration biopsy pathology results. Malignancy rates in each Bethesda group were calculated as 51.5%, 36.5%, 70.3%, 65.7%, 76.0% and 100.0%, respectively. Conclusion: Preoperative findings, operative features and pathological examination results help determine the risk groups that may develop complications. The parathormone and calcium values measured in the first 24 hours after surgery can predict hypocalcemia in the early postoperative period, thus allowing close monitoring of patients at risk and early intervention when necessary. Intraoperative nerve monitoring has high specificity and negative predictive values in predicting postoperative normal vocal cord functions. Keywords: thyroidectomy, complication, hypocalcemia, cord vocal paralysis, intraoperative neuromonitoring