Our center has been using the da Vinci robotic surgical system since January 2016 and routinely performed RATS lateral thoracic approach under laryngeal mask anesthesia to treat patients with anterior mediastinal tumors in October 2016 after the RATS technique became mature. In addition, based on our experience with subxiphoid approach in video assisted thoracic surgery (VATS), we have also actively carried out subxiphoid approach in RATS under laryngeal mask anesthesia to treat patients with anterior mediastinal tumors.
Previous studies have shown that both subxiphoid and lateral thoracic approaches have a high safety profile in VATS resection of anterior mediastinal tumors[6,7]. However, there are few studies comparing the efficacy and safety of subxiphoid approach and lateral thoracic approach in RATS. However, there are no studies comparing the efficacy and safety of the subxiphoid approach and the lateral thoracic approach to RATS under mask anesthesia. Therefore, in the present study, we retrospectively analyzed the short-term efficacy and safety of anterior mediastinal tumor resection by RATS under laryngeal mask anesthesia with different approaches in our single medical group.
Unlike tracheal intubation, the i-gel laryngeal mask does not enter the voice box and the following trachea, which is easy to operate, low irritation and low stress reaction, and less airway and pharyngeal complications. In this study, only one case of mild sore throat occurred in the lateral chest group after surgery, and no hoarseness or choking cough with drinking water occurred. It has also been shown that i-gel mask placement produces less cortisol, interleukin-6, tumor necrosis factor-α, and endocannabinoids than tracheal intubation, reduces systemic inflammation and oxidative responses[8], and has less hemodynamic impact[9]. However, the airway seal of the i-gel laryngeal mask is poorer than that of the tracheal intubation and cannot achieve one-lung ventilation. To ensure a good surgical view, we often add a 6-8 mm Hg artificial pneumothorax at the same time, leaving the lungs in a semi-atrophied state. The anesthesiologist does not need to deliberately small tidal volume high frequency ventilation, if the intraoperative lung tissue atrophy on the operative side is poorly affected by the surgical field, the tidal volume can be appropriately reduced under the condition of ensuring good oxygenation, and if necessary, a bronchial occluder can be used in combination with the application of protective ventilation mode. This ensures the safety of the procedure while improving patient comfort and reducing pharyngeal and airway complications.
The results of this study showed that there was no statistically significant difference between the subxiphoid group and the lateral thoracic group in terms of total operative time, but the docking time was slightly longer in the subxiphoid group than in the lateral thoracic group. In terms of intraoperative bleeding, there was no significant difference between the two groups. According to the author's profound experience, the RATS lateral thoracic approach and subxiphoid approach have significant advantages in reducing intraoperative bleeding than the VATS lateral thoracic approach and subxiphoid approach we used in the past. The main reasons for the advantages of RATS in terms of surgical bleeding may be: firstly, RATS provides tenfold magnification of the 3D visualized images and superior imaging quality, which facilitates intraoperative identification of various structures; secondly, RATS allows free joint movements of the robotic arm and provides seven degrees of freedom of movement through its wrist, allowing the surgeon to operate in a stable and comfortable environment, resulting in more precise dissections and avoiding nerve and artery damage; thirdly, RATS offers advantages in suturing and facilitates the operator's management of intraoperative bleeding.
The subxiphoid approach maintains the integrity and stability of the thorax, the absence of bony structures around the xiphoid process facilitates the removal of the specimen, and it does not operate through the intercostal space, avoiding injury to the intercostal nerves and reducing postoperative pain[5]. The results of this study showed that the subxiphoid group was more advantageous in terms of total postoperative drainage, postoperative drainage time and postoperative hospital stay compared to the lateral chest group. The subxiphoid approach reduces pleural injury and leakage from small lymphatic vessel breaks in the chest wall, and the pathway for pleural effusion production is reduced, which can reduce the total postoperative drainage[2]. In addition, the author believes that since patients with subxiphoid approach have less postoperative pain, which facilitates active coughing and coughing and early bed activity, there is less drainage and patients can have their drains removed earlier. At the same time, due to earlier detubation, the patient's subjective pain is significantly reduced, so that he or she does not experience reduced breathing due to pain and poor cooperation with postoperative mechanically assisted sputum evacuation, which in turn affects postoperative pulmonary resuscitation; since there is no restriction of bedside drainage bottles, it is easier for patients to get out of bed and reduce the incidence of crushing pneumonia due to prolonged bed rest; at the same time, the incidence of infection is reduced because the drainage tube is connected to the outside world and bacteria have the opportunity to travel retrograde through the drainage tube and cause infection in the chest cavity[10]. In addition, getting out of bed early also accelerates intestinal motility, promotes the patient's intake of high-quality protein, and speeds up postoperative recovery, therefore shortening the postoperative hospital stay, which is what accelerated rehabilitation surgery advocates[11].
In terms of postoperative pain VAS scores, the subxiphoid group was superior to the lateral thoracic group on postoperative days 2 and 3, while no significant difference was seen between the two groups on postoperative day 1. There are two main sources of postoperative pain for patients: first, pathological pain in the muscles, fascia and nerves of the incision in the operative area; second, postoperative pain caused by friction and pulling of the drainage tube opening. In our center, analgesia is routinely administered intravenously by analgesic pump in the postoperative period. The prolongation of tube duration in the lateral chest group will aggravate the continuous irritation of the pleura and the tube opening by the drainage tube, aggravate the patient's pain, and affect the postoperative cough and sputum, night sleep and postoperative bed activity, thus prolonging the length of postoperative hospitalization and increasing the patient's financial burden. In addition, the author believes that because the operating hole of the lateral thoracic group is located between the ribs in the anterior axillary line and the midclavicular line, where the intercostal muscles are thicker and the distribution of intercostal nerves and blood vessels is richer than that of the subclavian approach, the subjective pain is more significant compared with the subclavian approach. In terms of postoperative complications, the incidence of the subxiphoid group was slightly lower than that of the lateral thoracic group, but the difference between the two groups was not statistically significant.
The lateral thoracic approach in our center generally uses the right intercostal approach, which provides a relatively larger operating space on the right side of the chest compared to the left intercostal approach, a better surgical field of view, and importantly, a higher level of safety by avoiding structures such as the heart and the aortic arch[12]. If the thymic tumor is clearly protruding from the left side of the chest, the left intercostal approach is the more appropriate and safe choice[13]. In our experience, the advantages of the sword bursting down the entry path in RATS are as follows: good visual field, good exposure; more flexible robotic arm, less tremor, safer; more complete tumor resection, more thorough clearance of anterior mediastinal fat (for thymoma, the subxiphoid approach allows observation of the thymus bilaterally, enabling more thorough and safe dissection of the thymus and its surrounding fatty tissue); easier removal of the specimen; more aesthetic incision, less pain, more acceptable to younger patients. In addition, although none of the cases included in this study had an intraoperative intermediate chest opening, the subxiphoid approach does not require lateral positioning and would be faster than the lateral chest approach if an emergency chest opening is required to stop bleeding in the event of unexpected hemorrhage during surgery. We have applied sternal pulling hooks in some cases, and the sternal pulling hooks greatly take advantage of the subxiphoid approach and further expand the visual field space. In the case of obese patients, the subxiphoid approach can be limited. It has been reported[14] that the learning curve for subxiphoid approach in RATS for resection of anterior mediastinal tumors is 10-20 cases to reach plateau, and in our experience with extensive VATS experience, plateau can be basically reached after 10 procedures.
The present study has certain limitations and shortcomings: (Ⅰ) the results may be biased because the data source of the included studies is single-center and the sample size is relatively small for retrospective studies; (Ⅱ) in this study, considering the small surgical area, the three-hole technique can better avoid mutual collision and interference between surgical instruments and is more conducive to surgical operations, and the less traumatic single-hole technique will be tried in the future; (Ⅲ) long-term survival analysis is lacking in this study, and further data refinement through follow-up is proposed.