LAUSR

Dear Editor, Various approaches to endoscopic and robotic thyroidectomy have been developed over the last two decades in order to reduce or avoid the formation of scarring on the anterior neck, which is a concern for patients, especially Asians. Generally, carbon dioxide (CO2) is used as gas insufflation in most laparoscopic procedures, including endoscopic and robotic thyroidectomy. With the benefit of inertia, non-inflammable, absorbable in circulation and then excreted by exhalation, CO2 is ideal for laparoscopic gas insufflation [1]. In laparoscopic abdominal surgery, the gas is insufflated into the abdominal cavity and rarely causes any major problems. However, endoscopic thyroidectomy is performed by creating an unnatural working space between the muscles and subcutaneous fat of the neck area. As a result, subcutaneous emphysema may develop with inappropriate settings [2–4]. Subcutaneous emphysema has been defined as having air tapping in the subcutaneous fat and can be palpated as the crepitus over the skin. This condition can also be found in pneumothorax patients. However, subcutaneous emphysema found after endoscopic thyroidectomy is different because this condition is caused by direct CO2 insufflation. Thus, the only management for this condition is conservative treatment. Close observation and oxygen supply should be given. The CO2 will eventually be absorbed and excreted from the body through exhalation within 24–48 h, without complications. For this reason, most endoscopic and robotic thyroidectomy techniques typically employ CO2 for gas insufflation [5, 6]. Since thyroid natural orifice transluminal endoscopic surgery (NOTES) has increased in popularity, we developed and have continued to refine the transoral endoscopic thyroidectomy vestibular approach (TOETVA) since 2014 [7]. Our continued work has been reported with no gasrelated complications [8, 9]. The only problem with the transoral thyroidectomy procedure was reported by Wilhelm et al. in their series using a sublingual approach [10]. One case (12%) of mediastinal emphysema was found and treated by conservative management. No other major complication was observed. In a series of TOETVA by a Taiwanese surgeon, 38.8% were found to have subcutaneous emphysema that required staying in the PACU [2 h. This was because some patients developed stridor or difficulties in breathing. However, no major complications related to insufflation were found. In that report, 6 mmHg pressure was insufflated [11]. However, gas flow setting was not reported. This is noteworthy because the setting of pressure and gas flow is critical in preventing insufflationrelated issues. In our series, more than 600 patients received TOETVA, with only 10 cases developing simple subcutaneous emphysema by palpating of the crepitus at the anterior chest well. No other respiratory symptoms were observed. No mediastinal emphysema, pneumothorax, or CO2 embolism occurred. Thus, only conservative management was needed. In our hospital, the following points of strategy for TOETVA are now used for the prevention of problems: (1) There were experimental reports in pigs showing that the upper limit for CO2 pressure should not exceed 10 mmHg in endoscopic thyroidectomy [2, 12]. Another human series confirmed that \9 mmHg was considered & Angkoon Anuwong [email protected]