A prospective observational study of anaesthesia practices in esophageal cancer surgeries with intraoperative nerve monitoring.

Surgical esophagectomy is a curative treatment for cancers involving lower and middle esophagus. During an esophagectomy, injury to the recurrent laryngeal nerve (RLN) is likely due to the proximity of the nerve to the oesophagus in the trachea-esophageal groove. The recurrent laryngeal nerve Is a branch of the vagus nerve that provides sensory and motor innervation to the larynx, including its muscles and structures. Right RLN branches from the vagus nerve around the T1- T2 level, then loops under the right subclavian artery and moves back up through the neck. Left RLN arises anteriorly at the arch of the aorta, then loops under the aortic arch and moves back up through the neck. The RLN innervates all the intrinsic muscles of the larynx, except for the cricothyroid muscle, which is innervated by the superior laryngeal nerve. RLN also carries sensations from the laryngeal mucosa on the undersurface of vocal cords and subglottis. Injury to RLN results in varying grades of nerve dysfunctions and vocal cord palsy. Following an injury to RLN, adduction of the vocal cord gets affected and the vocal cord remains in the paramedian position, resulting in the phonatory gap between the two cords. It results in the hoarseness of the voice, ineffective cough and increases the possibility of aspiration of food contents in the lower airway. It significantly affects postoperative morbidity and mortality following esophageal surgery. The current incidence of RLN injury during esophageal surgery varies from 5-15%.1 Various surgical and disease-related factors affect the incidence of RLN following esophagectomy surgery. RLN injury is more common in tumours involving the upper and middle oesophagus. McKeown’s esophagectomy carries a higher risk of RLN injury as compared to Ivor-Lewis’s approach of esophagectomy. Three-field lymphadenectomy (i.e. resection of abdominal, mediastinal and cervical lymph nodes) carries a higher incidence of RLN injury as compared to the two-field approach (i.e. resection of abdominal and mediastinal lymph nodes) of lymphadenectomy during oesophagal surgery. Intraoperative monitoring of RLN (IONM) helps the surgeons to identify the nerve fibres during the surgical resection and to preserve them. RLN monitoring during the surgery needs a few modifications in the anaesthesia techniques- viz. minimal use of muscle relaxant, use of a special endotracheal tube that carries surface sensors to identify vocal cord movements, limiting the use of inhalational anesthetic agents etc. It also involves the active participation of neurophysiologists during the surgery. At Tata Memorial Hospital, we conduct nearly 180 esophagectomies every year. IONM is conducted in suitable case (approximately 25 cases per year). During the surgeries that require IONM, the neuromuscular blockade is avoided. The depth of anaesthesia is maintained by either inhalational anaesthesia (up to 1 MAC) or by total intravenous anaesthesia using intravenous propofol. A special endotracheal tube (endotracheal tube with surface sensors on its surface to detect vocal cord movements) is used for these surgeries. Hence, we wish to conduct a prospective observational study to find out the anaesthesia practices during IONM and their effects on the incidence of RLN injury following esophagectomy surgeries.