As a normal part of fetal circulation, the ductus arteriosus connects the aorta and the pulmonary artery to shunt blood away from the nonfunctioning lungs. Typically, this conduit will close on its own within the first few days of birth. In some infants, especially neonates, the ductus arteriosus remains open. The incidence rate of PDA in term infants is 0.057% (6). This persistent shunt, allowing blood to flow from the aorta into the pulmonary artery, can create high blood pressure in the pulmonary artery. The result of increased blood flow to the lungs and decreased blood flow to the rest of the body is lung injury and systemic effects such as cerebral hemorrhage, necrotizing enterocolitis and Eisenmenger's syndrome. Thus, intervention is recommended if PDA present. There are several options for PDA treatment; however, each method has advantages and disadvantages. There are many problems in the ligation or suture of PDA through posterolateral posterior incision, such as large trauma, slow recovery and scar formation (7). This type of ligation is still suitable for all kinds of PDA, including large PDA and window PDA. Drug therapy is only suitable for the treatment of PDA in premature infants (8). Interventional PDA occlusion has the disadvantages of radioactivity, the long-term existence of occluder in body, postoperative hemolysis, and limited MRI examination (9–12). These were also the main reasons why our patients chosen robotic surgical. Thoracoscopic PDA ligation has some disadvantages, such as conversion to thoracotomy, unclear intraoperative visual field, difficulty in detaching and ligating PDA, and intercostal pain (13–16).
The present study demonstrated that endoscopic PDA closure with robotically assisted instrumentation was technically feasible in children. Furthermore, dissection of the aorta, subclavian artery and ductus were performed easily and safely using EndoWrist instruments, including an articulated grasper, a hook-up cautery on a low energy setting, and articulated scissors, with no laryngeal nerve injuries or hemorrhage. Enhanced intracorporeal dexterity, optimized hand-eye alignment, and tremor filtering made tissue handling and dissection easy and accurate. Most importantly, there is stationary pivot point at the chest wall. This significantly reduced postoperative pain due to intercostal muscle traction and rib compression. Because there was no tension in the intercostal space and no thoracic drainage tube, there was no compression or traction on the intercostal nerve and subcutaneous tissue, inducing little pain and quick recovery. The patients could get out of bed 6 hours after the operation and leave the hospital on the first day after the operation. At the same time, there was no need to use antibiotics during the perioperative period.
Compared with the traditional endoscope, the fourth generation of robot surgical systems has the following advantages: Clear and accurate three-dimensional vision, Intelligent actions, Motion correction and jitter filtering, The surgeon does not need to go to the operating table to avoid crowding between the surgeon and the assistant or blocking the surgical field of vision. In our experience, with a small number of cases, patients aged more than 6 months and weighing more than 5 kg were chosen. In fact, patient younger than 6 months had been reported to be treated using robotic surgical technique (17). Moreover, the diameter of the PDA was less than 0.8 cm, which was considered safe for ligation even for a window-type duct. To date, the fourth generation of robot surgery systems (Da Vinci robot) has been widely used in adult urology, thoracic surgery, obstetrics and gynecology, general surgery, cardiac surgery, and so on [18, 19]. With the development of minimally invasive technology, the Da Vinci robot is even used in head and neck surgery (20). However, application of the Da Vinci robot in pediatric surgery is relatively restrictive because children's body cavity space is narrow and traditional procedures are not applicable. The progress of endoscopic surgery has gradually solved this problem, but there are still disadvantages for accurate operation. The Da Vinci robot can perform a perfect operation in a limited space, can reduce surgical injury, can improve the curative effect and can minimize pain in children. Therefore, the Da Vinci robot has advantages in the application of pediatric surgery. At present, the robot system is mainly used in pediatric urology. The history of robot application in pediatric cardiac surgery is relatively recent. El Bret first reported in 2002 that PDA was cut and sutured with robot assistance (21). PDA ligation through a robot system was also reported in 2005 by Yoshihiro Suematsu in Boston Children's Hospital (5). At present, there is no published report about the robot system used in pediatric cardiac surgery in China. The number of PDA ligation by Da Vinci robots is small. The indications and contraindications are relative. With the increasing number of patients, the indications of robotic PDA ligation may expand.
The selection of the position of the trocar placement was of very importance in the operation, owing to the poor position of the trocar inducing poor vision, difficulty in operation, and relative resistance between the manipulator's arms. In this group, the 4- trocar method effectively avoided interference from the visual field of the left upper lobe, and the method was safe for separating and ligating the PDA. In the early application period, the distance between the mirror trocar and the right main manipulators was too short in one case, resulting in confrontation between the two instruments. Thus, at that time, the operation was extremely difficult, and 85 minutes was required to complete the surgery. With the accumulation of experience, we also performed a 3-port operation without an auxiliary trocar. It was proved to be feasible. Due to lack of experience in the early stage of this group, we selected children aged > 2 years and weighing > 10 kg for surgical treatment. With the accumulation of case data, infants aged < 2 years or even infants can be considered for Da Vinci robot surgery. Except PDA procedure, the treatment of congenital heart diseases in children with the assistance of the Da Vinci robot is limited because of age and weight requirements for the establishment of cardiopulmonary bypass. In China, it is used only in the surgical treatment of atrial septal defects and in ventricular septal defects in older children (22). With the increasing number of patients, the indications of robotic PDA ligation may expand.
The magnification of the visual field can be adjusted according to the need for the intraoperative condition and the habit of the operator. After separating the upper and lower windows of the PDA, the vagus nerve and its recurrent laryngeal branch can be displayed and avoid to be injury during ligation. One patient had clinical symptoms of laryngeal nerve injury, such as hoarseness and choking cough. For this patient, it was thought that the recurrent laryngeal nerve injury duo to the mediastinal pleura and aortic adventitia were not separated effectively. Therefore, to avoid nerve injury, we separated the two layers as much as possible. It is better to sandwich the vagus nerve and its recurrent laryngeal branch between the two layers. The robot Endowrist function can effectively, safely and easily detach the posterior wall of PDA. In addition, a high-definition field of vision makes deep ligation quick and safe. One patient was found to have residual ductus arteriosus by echocardiography one month after the operation. Considering the large size of the ductus arteriosus, the ligation of the ductus arteriosus was not tight enough to result in residual ductus arteriosus. In the later stage, we ligated large PDA three times to prevent residual leakage. Meanwhile, esophageal ultrasound and transthoracic ultrasound were also needed to evaluate residual leakage.
Limitations
In our experience, robot-assisted PDA ligation also has the following technical restrictions. First, there is no force feedback during the operation of the manipulator, so special care should be taken in separating the posterior wall of the ductus arteriosus through the line of sight and the position sense of the instrument. When ligating the arterial duct, it is necessary to observe the tension of the silk thread closely to prevent the silk thread from breaking due to excessive force. Second, this technic requires a surgeon with at least ten years of experience to ligate the PDA in thoracotomy in case of a rupture of arterial duct tissue. In this group, the chief surgeon had more than ten years of experience in cardiac surgery, and there were no cases of massive bleeding, silk thread breakage, or conversion to thoracotomy. Fortunately, a previous study has commented on the learning curve for robotic surgery being shorter than that for endoscopic surgery (23). In addition, it’s reported that the presence of wristed instrumentation, tremor abolition and motion scaling enhanced dexterity by nearly 50% as compared with endoscopic surgery, and three-dimensional vision enhanced dexterity by a further 10–15% in addition to the 93% reduction in skills-based errors (24). Therefore, it is believed that robotic surgical technique would been more easer to master and accept. In addition, the average cost of robot-assisted endoscopic treatment of PDA surgery is US$8180. Because this surgical procedure has not entered medical insurance reimbursement, although the cost is not very expensive in most eastern China family, it may be considered a burden for families with relatively low economic levels. It is just an alternative to traditional approaches for some families with special requirements. It offers patients psychological and social satisfaction and quality of life without occluder device in body. We had tried our best to optimize the operation procedures. The cost of the surgery was reduced, to some extent, due to the cancellation auxiliary trocar. We hope that with the improvement of instrument technology, the cost of this operation will be reduced rapidly and applicable to all families. Lastly, PDA surgery through robotic systems has been performed based on a small number of patients in a single center. There is required multicenter experience in the future.