Background and Goal of Study:

Transcranial motor-evoked potential monitoring (Tc-MEP) causes bite injuries to the oral cavity including the endotracheal tube. We developed a mouthpiece to prevent these injuries, and reported its efficacy and safety [1]. After a pilot study, we started to use the mouthpiece routinely for elective cases. The purpose of this study was to examine the efficacy of the mouthpiece in clinical setting.

Materials and Methods:

After obtaining approval from our institutional review board, patients undergoing spinal surgery under Tc-MEP in our institute during 2013-2016 were enrolled. Patients were fitted with a bespoke vinyl-silicone mouthpieces by dentists before surgery. On induction of general anesthesia, the mouthpiece was attached to the upper and lower dental arches. A lateral cervical X-ray was taken at the end of surgery to examine the condition of the endotracheal tube. Deformation of endotracheal tube was defined as the ratio of inside diameters of the most stenosed and normal part of endotracheal tube less than 90%. The incidence of endotracheal tube deformation was compared with the patients in whom a conventional gauze bite block were used.

Results and Discussion:

Of the 279 patients, 108 were excluded due to the X-ray imaging failure. Of the remaining 171 patients, 140 patients used the mouthpiece while 31 patients used a conventional gauze bite block. The incidence of tube deformation in the patients with the mouthpiece (2 of 140 patients, 1.4 %) was significantly lower than in those with the gauze bite block (6 of 31 patients, 45.0 %; p < 0.001). Conventional gauze bite block were used in toothless cases and emergency cases. According to the present results, we should prepare the mouthpieces for those cases.

Conclusion(s):

The incidence of damage to the endotracheal tube caused by intraoperative transcranial motor-evoked potential monitoring was reduced by a novel mouthpiece.

References (optional):

1. Oshita K, et al: J Anesth 2016: 30(5); 850-854

11 / Prevention of bite injuries with novel mouthpiece during intraoperative transcranial electric motor-evoked potential monitoring in spinal surgery