Abstract
I would like your readers to be aware of a complication that can occur with the electromyographic (EMG) endotracheal tube (ET) that is used in recurrent laryngeal nerve monitoring.1 Most of the publications to date deal with the efficacy of laryngeal nerve monitoring in preventing temporary or permanent weakness of the recurrent laryngeal nerve in thyroidectomy.2 Complications related to the tube itself have not been studied in detail. I have been using the tube for all thyroidectomies and parathyroidectomies over the past three years (more than 300 cases) and have found the tube to be of invaluable assistance.
This is our first experience with a complication of right lower lobe lung collapse after insertion of an EMG ET. During induction of anesthesia, the left main-stem bronchus was intubated. The patient developed bronchospasm. This was corrected by replacing the ET tube and treating the bronchospasm. I thought it was appropriate to look at the possible causes and suggest ways of preventing them.
The anesthesia literature recommends that the upper end of the ET tube cuff be 2 cm below the vocal folds and the tip of the ET tube be 2 cm above the carina.3 There may be a 2-cm difference in the cuff-to-tip distance between a #6 and a #8 ET tube. In patients with short tracheas, better tube positioning is achieved by using smaller ET tubes (<8 mm internal diameter).4 A size 6 EMG ET has an outer diameter of 9 mm. The cuff-to-tip distance is also 5 mm longer than that of a non-EMG tube and has a sharper triangular edge. The manufacturer's instructions say “confirm the depth of intubation via the standard procedure for such tubes.” When the EMG tube is used in patients with short tracheas (11-cm cords-to-carina distance), the surgeon needs to verify that the tip of the tube is at least 2 cm above the carina. Being cognizant of the fact that the cuff-to-tip distance is 5 mm greater in the EMG tube than in a comparable non-EMG tube may help to prevent intubation of the main-stem bronchus. A flexible bronchoscope can be used to verify the correct position if necessary.5 A complication such as ours can easily be prevented.