Intraoperative Vagal Nerve Stimulation in a Patient with Long QT Syndrome during Thyroidectomy

Abstract

The 51-year-old female patient referred to our department with ultrasound images of a large thyroid nodule, with a major diameter of 3.66 cm, which had excessive vascularity, occupied the left lobe and descended to the upper mediastinum. Additionally, the blood tests revealed high levels of calcium, low levels of phosphorus and parathormone levels in the normal range. Because of the patient's history of nephrocalcinosis, the presence of primary hyperparathyroidism with normal levels of parathyroid hormone could not be excluded. The additional ultrasound mapping by an experienced radiologist in parathyroid glands imaging, was negative for abnormal parathyroid tissue. Therefore, there was an absolute indication for surgery including, not only thyroidectomy but bilateral neck exploration to reveal parathyroid hyperplasia or adenoma, as well. The family history of the patient included LQTS, which affected 3 generations. The mutant was located at long QT syndrome type 1 (LQT1). The investigation of the family started from the late 90's when the nephew of the patient had several episodes of loss of consciousness. Both the patient and her sister mentioned similar events in the past. Moreover, there was a third sister who suddenly passed away at the age of 15 during swimming. The patient's children and her parents were asymptomatic. After a thorough family examination, the conclusion was that they had a mutant at LQT1, as mentioned above, and according to Schwartz criteria, 3 members had the clinical diagnosis of the syndrome, including our patient. More specific, the latter's electrocardiogram (ECG) revealed sinus rhythm and corrected QT=461 msec. All the family members were administered of b-blockers for life. Because of the above history, there was a very thorough preoperative evaluation of the patient. All the potential intraoperative and postoperative risks were explained in detail to the patient, before she gave her signed informed consent form. The patient was led to the operative theater, while a special cardiologist was standing by and a defibrillator was ready for use. Since continuous intraoperative ECG recording was not available, the attending cardiologist performed manually ECGs at specific time intervals, according to surgeon's vagus nerve stimulation activity (Fig. 1). Moreover, ECG recording was performed at the induction to anesthesia and after patient's extubation, according to anesthesiologist's instructions. Patient underwent a total thyroidectomy and dissection of hyperplastic left upper parathyroid gland of a major diameter of 1.3 cm. Intraoperatively, after the mobilization of the left lobe, the vagus nerve was identified and stimulated with 1.5 mA, in order to exclude equipment failure or misplacement of the endotracheal tube, and to set an initial signal which would be used as a baseline. Afterwards, before its exposure, the RLN was localized by stimulating nearby and parallel to the trachea. Then, dissection and full exposure of the RLN by taking signals at all its revealed course followed. During the dissection, the vagus nerve was frequently stimulated, in order to exclude any proximal injury of the RLN. At the end of the lobectomy, the vagus nerve was stimulated as well as the RLN, and its signal remained similar to the initial one, which confirmed the anatomical and functional integrity of the RLN. An upper left hyperplastic parathyroid gland was also identified and was excised. The same procedure was followed during the right lobectomy. After thyroidectomy and parathyroidectomy completed and at the end of the hemostasis, laryngeal and vagus nerves were stimulated bilaterally, before the closure of the incision. Also, parathyroid hormone levels were measured intraoperatively 10 and 20 minutes after the excision of the abnormal gland, showing a decrease more than 50%, confirming the biochemical cure of the patient. Postoperatively, the patient was admitted to the intensive care unit and was put on monitoring for preventative reasons for 24 hours. Her postoperative course was uneventful and she was discharged after 48 hours. 46