This is the first cohort study on subxiphoid NI-VATS mediastinal tumor resection, which indicated that NI-VATS was a safe and feasible procedure via subxiphoid approach. Although statistically significant was not observed because of small sample size, NI-VATS might potentially decease perioperative complication compared with I-VATS (7/21 vs 11/19). It can be considered as an alternative to I-VATS when lateral approach is not available or when surgeons preferred subxiphoid surgery.
Compared with the trans thoracic approach, the most prominent advantages of subxiphoid approach for mediastinal tumor are more visual and less postoperative pain. A complete resection of tumor is the primary aim. With the help of a camera scope inserted from the midline of the body, it would be convenient to look over the bilateral mediastinum clearly and confirm the location of important blood vessels and nerves nearby.  However, there are still some shortcomings of subxiphoid approach. First, a surgical team familiar with the subxiphoid approach procedure is needed. Second, it's hard to play when severe adhesions are existing. Third, the tumor size also need to be limited because of the narrow space. Therefore, the application of the subxiphoid approach may be restricted in some conditions.
The anesthesia process of the I-VATS group in subxiphoid approach is almost the same as it in other thoracic surgeries.  When using a double-lumen tube for one-lung ventilation, contralateral lung collapse is easy to achieve via gentle press by a surgeon and air suction by an anesthesiologist. Nonetheless, the anesthesia process of the NI-VATS group under subxiphoid approach is a novel attempt. There was only one case report about subxiphoid NI-VATS for thymectomy in 2017; the patient was selected carefully, which indicating that NI-VATS in subxiphoid approach was still under exploring. The present study indicated that NI-VATS under subxiphoid approach was a feasible procedure with similar intraoperative and postoperative outcomes with conventional I-VATS group, which
Spontaneous ventilation during surgery relies on the integrality of at least one side of pleura. The way of three-port subxiphoid approach in our study cuts bilateral mediastinal pleuras, causing collapse of both sides of lungs, which made complete spontaneous ventilation impossible. When there is bilateral pneumothorax at the same time, mediastinal swing would stop, followed by a continuous deflation and inflation of bilateral lungs, which would bring great challenge to the surgeon. To alleviate this problem, we adopted a small tide volume (3-4L/min) ventilation through SIMV mode, which would not only maintain the oxygen supply but also minimize the impact on the operation.
Non-intubated anesthesia management for subxiphoid approach actually includes laryngeal mask airway general anesthesia (without muscle relaxant) in SIMV mode, combined with vagus and intercostal nerve blocking. The laryngeal mask could potentially avoid intubation-associated complications, including postoperative sore throat, hoarseness and irritating cough. Besides, the difficult intubation is not uncommon in thymoma patients, rendering a laryngeal mask the preferred option.[6, 7]
Not using muscle relaxants is benefit for myasthenia gravis patients, which can avoid the residual effects of muscle relaxants, achieve faster recovery of respiratory muscle function and lower the incidence of difficult postoperative extubation. The benefits of omitting muscle relaxants are not limited in myasthenia gravis patients, it was reported that the use of muscle relaxants was associated with an increased risk of postoperative pulmonary complications, which cannot be reduced by the administration of reversal agents like sugammadex. In addition, muscle relaxants during large anterior mediastinal tumor resection would cause airway collapse, NI-VATS would potentially avoid this situation.  Although no airway collapse or prolonged extubation case occurred in our study, it could happen when the mediastinal mass is big. One of the important meanings of this study is to prove the feasible and safety of NI-VATS under subxiphoid approach. When surgeons confront a situation when convention I-VATS may have the high risk of causing airway collapse, he/she could also use NI-VATS via subxiphoid approach.
There are several limitations in our study, including small sample size, short follow-up and retrospective nature. Because the process is relatively novel, the steps are unfamiliar, and good cooperation is needed between the surgeons and the anesthesiologists, this new approach was not commonly performed.