This chapter discusses the minimally invasive repair of a Bochdalek (posterolateral) congenital diaphragmatic hernia (CDH) and an anterior Morgagni diaphragmatic hernia.
Bochdalek Diaphragmatic Hernia
Bochdalek hernias develop in early gestation and are located in the posterolateral aspect of the diaphragm. They are associated with pulmonary hypoplasia and pulmonary hypertension. These two factors conspire to create the major morbidity of respiratory failure associated with this fragile patient group. The lungs of patients with Bochdalek CDH demonstrate a more immature histology, with decreased arterioles and airway branching. Although the mass effect exerted by the abdominal viscera in the chest can cause mediastinal displacement, the primary physiologic problems are pulmonary hypoplasia and associated pulmonary hypertension. The traditional operative approach to a Bochdalek CDH has been transabdominally through a subcostal incision or, less commonly, through a low lateral thoracotomy incision. The defect is closed primarily, if possible. If the diaphragmatic defect cannot be closed primarily, various synthetic materials, as well as muscle flaps, have been used to bridge the gap. Both the laparoscopic and thoracoscopic approaches for Bochdalek CDH repair have been described. We prefer the thoracoscopic approach because of the ease of reduction of the abdominal viscera using the CO 2 insufflation, favorable sewing angles, and clear visualization of the hernia defect.
Indications for Workup and Operation
A Bochdalek CDH is often diagnosed prenatally. After the infant is born, a chest radiograph confirms the diagnosis. To prevent distension of the hollow viscera in the chest, early placement of an orogastric tube for decompression is important. Rarely, infants can be allowed to breathe with low levels of oxygen supplementation. Most require additional ventilatory support with endotracheal intubation. An experienced team focused on minimizing barotrauma and volutrauma is critical to successful management. The initial workup for infants with a posterolateral CDH includes an echocardiogram (ECHO) to evaluate for possible congenital heart disease and to quantify the degree of pulmonary hypertension. A baseline ultrasound of the head is also obtained in anticipation of the potential need for extracorporeal life support (ECLS). In the past, repairing this defect was thought to be a surgical emergency. The timing of repair is debated heavily in the literature, with some groups advocating early repair on ECMO and others (including our own) choosing delayed repair after the pulmonary hypertension has improved.
Clinical improvement includes a decreased oxygen requirement, minimal vasopressors, minimal ventilator support, and subsystemic pulmonary pressures as determined by ECHO. This is particularly important for the minimally invasive approaches to repair that use CO 2 insufflation. If the patient requires ECLS, thoracoscopic repair is delayed until the patient is decannulated and on conventional respiratory support. Contrary to some opinions, it is our feeling that prior ECLS is not a contraindication to thoracoscopic repair. Thoracoscopic repair while the infant is cannulated on ECLS poses issues related to logistics and operative location and is regarded as unsafe because of the risk of perioperative bleeding.
Thoracoscopic Bochdalek hernia repair is performed under general anesthesia. Standard endotracheal intubation is used. There is no need for single-lung ventilation as there is ample working space in the chest because of the pulmonary hypoplasia. Contralateral mainstem intubation should be avoided, as barotrauma and pneumothorax on the contralateral side could prove fatal. Appropriate anesthetic monitors are placed, including an arterial line through which blood pressure and blood gases can be monitored.
The infant is positioned transversely at the end of the operating bed in a near-lateral decubitus position (at approximately 70 degrees) to allow access to the abdomen if conversion to a laparotomy is necessary. The operating surgeon and assistant stand at the patient’s head with a monitor placed at the infant’s feet ( Fig. 33-1 ).
Initial access to the thoracic cavity is obtained with a Veress needle in the third or fourth intercostal space in the posterior axillary line, anterior to the tip of the scapula. The chest is insufflated to 3 to 5 mm Hg using CO 2 at a flow rate of 1 L/min. This is very well tolerated by almost all infants. We have had neither problems with induction of clinically significant pulmonary hypertension nor any other hemodynamic perturbations. A 4-mm port is introduced at this site, and a 30-degree 4-mm telescope is inserted. Two additional 3- or 4-mm cannulas are inserted just inferior and to the right and left of the initial port site ( Fig. 33-2 ), in the fourth or fifth intercostal space. Occasionally, we forgo the use of cannulas and place the instruments directly through the chest wall. The right-handed instrument is positioned in the anterior axillary line, and the left-handed instrument is situated more posteriorly. Ample working space exists in the chest because of the ipsilateral lung hypoplasia.
The abdominal viscera are gently reduced into the abdomen using blunt graspers, with care taken to avoid injury to the bowel or herniated viscera. It is important to remember that the peritoneal space is in the 3-o’clock position as this portion of the case is performed. The viscera should be reduced anterior to the position of the kidney. The spleen is the last structure to be reduced, acting like a cap to hold the hollow viscera at bay until the muscle edges are approximated. If present, a hernia sac can be used to help with the reduction of the viscera. Our usual practice is to remove the hernia sac. However, this step may be optional if the sac is inverted on the abdominal side of the hernia. If the patient experiences hypercarbia that cannot be managed by adjusting the ventilator, the insufflation can be stopped altogether after the viscera have been reduced. Often, the posterior rim needs to be freed from its retroperitoneal attachments to appreciate the full extent of the muscle tissue that is present. This maneuver frequently unfurls a substantial amount of hidden muscle that aids in closure. The entire rim of diaphragmatic muscle that will be in apposition should be scored with a hook cautery, making the peritoneal surfaces more prone to healing when approximated. The defect is then closed with interrupted sutures, starting medially and moving laterally. The suture needles can be introduced through the chest wall to avoid dulling the point by dragging them through a 3- or 4-mm port. Alternatively, an RB-1 needle can be flattened to a “ski” shape that passes through the port with minimal resistance.
Our current practice utilizes 2-0 silk sutures to close the defect. We now reinforce all primary repairs with six-ply Biodesign (Cook Inc., Bloomington, IL) (see later). The size of the reinforcement patch is approximately 1 cm in diameter wider than the defect itself, allowing the edges of the mesh to extend beyond the rim of muscle closure. A small bite of this mesh is taken centrally during the closure to prevent its displacement ( Fig. 33-3 ). As the suture line extends laterally, it may become more difficult to place the sutures. Suturing of the lateral portion of the defect can be made easier by having an assistant put external pressure on the lateral chest wall to bring the tissues in line with the instruments ( Fig. 33-4 ). The lateral corner stitch may be brought around the rib, if necessary, as can be done with the open approach. Usually, this is accomplished by making a nick in the skin where the needle is to be inserted into the chest cavity. The needle is then introduced extracorporeally through the chest wall and grasped intracorporeally. It is passed through both leaflets of diaphragm (and reinforcement mesh) before being driven back out the chest wall on the opposite side of the rib. Importantly, the needle is not pulled completely through the skin. When the back end of the needle is in the subcutaneous tissue, it is backed out the original hole such that both strands are exiting a common incision in the skin ( Fig. 33-5 ). An RB-1 or SH needle works well for this suture.