Initial Increase in Cuff Pressure in Anterior Cervical Spinal Surgery

When the retractor blades oped and is positioned to provide the surgical access in the anterior cervical spine surgery, it cause the trachea to deviate laterally and pose pressure on the tissue between the retractor and the trachea. This is convincible as revealed by the increase of cuff pressure of endotracheal tube. The study aims to investigate differences in the increase of cuff pressure after retractor is positioned between nasotracheal and orotracheal intubation.

When the retractor blades oped and is positioned to provide the surgical access in the anterior cervical spine surgery, it cause the trachea to deviate laterally and pose pressure on the tissue between the retractor and the trachea. The most important structure is the recurrent laryngeal nerve. This is convincible as revealed by the increase of cuff pressure of endotracheal tube. The pressure created by the retractor may be related to postoperative dysphonia and dysphagia. In view of minimizing the pressure created by the retractors, some neurosurgeons advocate to deflate then to inflate the cuff of ETT tube after the retractor is on, while some advocate monitoring of cuff pressure and keep below 25 mmHg. Nasotracheal or orotracheal tube can both be applied to general anesthesia for the anterior cervical spine surgery. The option depends on the surgeons' preference. Though both approaches end at the trachea, the nasotracheal tube is fixed at the nostril, and orotracheal tube, at the mouth angle, on the opposite side of surgical approach. The investigators hypothetize this difference in location results in different degree of deviation and increase of cuff pressure. The study aims to investigate differences in the increase of cuff pressure after retractor is positioned between nasoendotracheal and oroendotracheal intubation. Apfelbaum and colleagues indicated the asymmetric position of the oroETT within the larynx as being fixed distally by the cuff and proximally by taping at the mouth angle. The asymmetry of the tube shaft and cuff may contribute to unilateral vocal palsy. When the retractors are set up for ACCS, the deviation of cuff towards the retractors increases ETCP and creates a extrusion compression of tissues in between the cuff and the retractor blade. Nasotracheal intubation follows a more natural trajectory into the trachea. In theory, a nasoETT is more centrally located and less asymmetric in the thyroid cartilage and trachea; thus pressure from this tube may be relatively evenly distributed, and the pressure on the surrounding tissues is lower. Therefore, we hypothesised lower degree of tissue compression with a nasoETT, even during retractor splay. The effect may be reflected in intraoperative ETCP or post-ACCS dysphonia. This randomised controlled clinical trial assessed the differences in the tracheal intubation mode on the maximal ETCP during retractor splay (primary endpoint) and post-ACSS dysphonia (secondary endpoint).