Complications of Pediatric Minimal Access Surgery
Matias Bruzoni, MD, Craig T. Albanese, MD, MBA
Minimal access surgery (MAS) in the pediatric population has progressed immensely over the last 20 years, and more than 80% of the pediatric surgeons in North America are now performing laparoscopic and thoracoscopic procedures.1 Smaller and more precise technology has helped surgeons adapt to the limited space that the small patient’s chest and abdomen offer. However, these techniques require new and different skills that are not free of errors or complications.
The main difficulties surgeons face when performing MAS are more pronounced when operating in smaller spaces. These inherent limitations include 2-dimensional images; minimal haptic feedback (direct touch); operating at a distance with very thin instruments; motion parallax and poor ergonomics, such as limitations in directional movement and mobility of the instrumentation.
The safety of minimally invasive surgery in children has raised much concern and yielded multiple studies. Studies have shown variable rates of complications including bowel perforation, abdominal wall hematoma, pneumothorax, iliac vessel laceration, liver laceration, stomach perforation, bladder perforation, trocar-site herniation, and gas embolism.2-7 Most complications are related to the method of entry of the laparoscope.8 Fortunately, these most serious complications are rare. Historically, the incidence of bowel perforation has been reported as 1.8 per 1000 cases, and the incidence of major- abdominal-vessel and anterior-abdominal-wall vessel perforation has been reported as 0.9 per 1000 cases.9 Most of the common errors and complications that occur in pediatric MAS can usually be avoided by proper patient selection, adequate patient positioning, proper trocar alignment, availability of modern equipment, and careful equipment settings.
This chapter will focus on those complications that are unique to pediatric MAS technology, such as those related to abdominal and thoracic access, positioning, trocar insertion, instrumentation, and gas (CO2) insufflation. In addition, select procedure- specific complications will be discussed.
Many surgeons believe that the operation actually starts at the very first encounter with the patient. A safe surgeon should start planning the surgical approach before going to the operating room. A minimally invasive operative approach often requires a maximally invasive preoperative approach, and we believe that appropriate patient selection is crucial to avoid complications. For example, children with severe cardiac and pulmonary disorders may not be able to tolerate the physiologic stress of the reduction in functional residual capacity and hypercarbia associated with gas insufflation or single-lung ventilation during thoracoscopy, although there are reports of successful MAS in patients with single-ventricle physiology.10,11 Another poor candidate would be a child with a significant coagulopathy. Persistent oozing significantly limits visibility because the hemoglobin absorbs the xenon light. Very low-weight infants are also a challenge given the fact that the operative space is even more limited. It will be up to the surgeon to weigh the risks and benefits of the procedure and decide which approach to perform.
Previous open operations used to be an absolute contraindication to MAS. Presently, it is considered a relative contraindication, because newer technology and advanced experience allow safe access to the thoracic or abdominal cavities with either an open technique or Veress needle insertion at a site remote from the previous incision. Whether the proposed procedure can be carried out is solely a function of the anatomy and the surgeon’s experience when dealing with adhesions using minimal access techniques.
Another relative contraindication is bowel obstruction due to poor visualization and the risk of perforation when handling the bowel, both by virtue of the distended bowel.
Again, the surgeon’s experience and the use of novel atraumatic bowel graspers make many of these procedures feasible and safe.
One of the limitations of MAS is adequate retraction and exposure inside the abdominal or thoracic cavities. An operation that has poor exposure will make even the most experienced surgeon struggle. In MAS, operative field exposure is principally achieved using creative patient positioning techniques (ie, gravity). As in open surgery, the surgeon usually stands facing the structure to be operated on with the monitor “in-line,” directly in front of the surgeon. Given the requirement in advanced laparoscopic procedures for the surgeon to be able to use both hands for dissection and suturing, this often requires the surgeon to be positioned at a variety of places around the operating table, depending on the procedure. For instance, a laparoscopic fundoplication requires the surgeon to stand at the feet of the patient. This manner of positioning can be accomplished in multiple ways. Low lithotomy positioning using stirrups is appropriate for children over the age of eight. Attention must be paid to carefully positioning and padding of the lower extremities to avoid peroneal nerve injury or stretch injury to the femoral nerves. In smaller children, the head or foot of the bed can be removed to minimize the distance between the child’s head and the anesthesiologist. Even with this technique, the child will still be far away from the anesthesiologist, so additional care should be taken to ensure that the endotracheal tube is well secured to avoid dislodgement.12,13
In children under the age of 8 years, a supine, frog-leg position is more suitable than lithotomy. This positioning may be achieved by placing the child near the foot of the bed or turning the patient 90 degrees on the bed, which is most applicable for neonates.
Removing the head of the bed or lowering the foot of the bed will bring the anesthesiologist into the closest proximity possible to the child.12,13 If a child is going to be placed in a reverse Trendelenburg position so that gravity can reduce the bowel from the surgical field, as is often the case for fundoplication, cholecystectomy, and splenectomy, the use of a beanbag molded such that there is a “seat” is recommended so that a steep tilt will not cause the child to slide on the table. It is important when using a beanbag that the bag itself is secured to the table so it does not slide with the table movement.
Improper positioning during thoracoscopy can lead to complications and poorly performed, if not technically impossible, procedures. As with all thoracic procedures (regardless of technique), all bony prominences and the axilla need to be padded to avoid pressure sores and brachial plexus injury. Access to the anterior mediastinum is best gained by positioning the patient supine and elevated 30 degrees. Procedures like lung biopsy or lobectomy are best accomplished with the full lateral decubitus position.
Procedures involving structures in the posterior mediastinum are approached with the patient prone and elevated 30 degrees. In this way, anterior and posterior nonpulmonary structures can be easily accessed without the use of a lung retractor, because the combination of gas insufflation, single-lung ventilation, and gravity will keep the lung out of the surgeon’s way, necessitating the use of no more than 3 trocars for most procedures.
Understanding of the anatomy of the abdomen and pelvis can help minimize serious vascular injury, for example the aorta and vena cava bifurcate just inferior to the level of the umbilicus. Thus, a trocar inserted perpendicular to the spine risks injury to these structures. A trocar inserted in a more tangential and lateral direction avoids these 2 structures.
The foremost anatomical consideration is the smaller surface area for access in smaller children and the smaller operating field within the abdominal, thoracic, and retroperitoneal spaces. Additionally, the small child’s abdominal wall tends to be thinner and more compliant compared with that of adolescents and adults, which must be remembered when gaining trocar access with a Veress needle. In either situation, attention should be paid to the possibility that the umbilical vessels and urachus may still be patent and that the epigastric vessels could be easily injured given the small cross- sectional area available for trocar access.2,7,14-18 The liver margin is well below the ribcage in small children, the abdominal viscera are closer to the abdominal wall in children, and the bladder lies in an intraabdominal position rather than in the pelvis in children.14 The stomach should be deflated with a gastric tube. The bladder can be emptied by using either an indwelling catheter or by manual pressure (useful for neonates and very small children), called the Credé maneuver.13-15 These anatomical considerations affect the choice of trocars and their route of insertion and location.13,15-17 In addition, the retroperitoneoscopic approach for nephrectomy, ureteropelvic junction obstruction, and adrenalectomy, as opposed to transperitoneal MAS, is limited by a smaller working space, crowding of trocars, and a relative lack of anatomical landmarks.
Thoracoscopic procedures in small children are challenged by the small, rigid chest wall with minimal inter-rib space. It is often necessary to collapse the ipsilateral lung to develop an appropriate working space. The available methods for single-lung ventilation, depending on the patient’s size and the anesthesiologist’s expertise, are double lumen endotracheal tube (reserved for children >10 years), selective main stem intubation (sometimes requiring the aid of fiberoptic bronchoscopy), and intratracheal intubation with main stem occlusion by a bronchial blocker.19With all these methods, it is desirable to add 4mm Hg to 6mm Hg of CO2 pressure at low flow (eg, 1L/min) to maximize lung collapse. This minimal pressure rarely results in hemodynamic or respiratory compromise. In neonates, the lung can often be collapsed by simply using this controlled pneumothorax without the aid of selective ventilation.
TROCARS AND TECHNIQUE OF INSERTION
Trocar insertion and placement are essential to the successful completion of an operation. More frequent than causing a complication, poor trocar positioning may cause frustration even to an advanced laparoscopic surgeon. This can lead to an ergonomically challenging procedure with a longer than usual operative time.
The nature of the abdominal wall in children can influence the surgeon’s choice in trocar type and method of insertion. The open or Hasson technique is widely performed due to the compliant abdominal wall and short antero-posterior distance in the thorax and abdomen. The Veress needle technique is quick and easy but has the possibility of injuries to blood vessels, bowel, urinary bladder (for laparoscopy) and heart, lungs, and diaphragm (for thoracoscopy). Once the first trocar is inserted, the rest of the trocars can be inserted under direct visualization. The trocar insertion technique is dictated mainly by the surgeon’s experience and comfort level rather than the technique itself. Almost every method of insertion has been paired with the different trocar systems, and all of them have risks of complications.20 A Cochrane database review was performed in 2008 that included 17 randomized controlled trials concerning 3040 individuals undergoing laparoscopy.21 Overall, no evidence was found of an advantage using any single technique in terms of preventing major complications. Based on evidence investigated in this review, there appears to be no benefit in terms of safety of one technique over another. However, the included studies were small and cannot be used to confirm safety of any particular technique.
Most of the catastrophic complications during MAS occur during insertion of the trocars. Injury to great vessels occurs in about 0.05% of trocar insertions, and the mortality rate from these injuries is up to 20%.22 For this reason, insertion should not be taken lightly and should be performed by someone with significant experience. Using both hands helps prevent the trocar from injuring a loop of bowel or a blood vessel. Gas embolism due to inadvertent puncture of a large vessel is extremely rare,23 and subcutaneous emphysema can occur by improper positioning of the needle or when a trocar is displaced into the abdominal or thoracic tissue space. This is rarely of clinical significance, although it can hinder port reinsertion or create pneumothorax or pneumomediastinum.
Using transillumination in a low lit operating room can show the location of vessels in the abdominal wall and help prevent hemorrhage from placing trocars through these vessels, especially the epigastric vessels.
The most common trocar used in pediatric MAS, is the radially expanding Step trocar (US Surgical, Norwalk, CT). These access devices come in 2 lengths, 75mm and 100mm. They are made to be inserted with a Veress technique to allow a snug fit when they are bluntly expanded or they can be placed with an open technique. This expandable sleeve starts at 1.7mm in diameter and can be increased to 3mm, 5mm, 10mm, or 12mm. They fit snugly and thus minimize the chance of gas leak and dislodgement from the thin abdominal/chest wall.7,16,24,25 When the device is removed, the tissues contract, leaving only a series of small slits with a fascial defect about half the size required for othertypes of trocars. With small defects, the risk of trocar-site herniation decreases and the cosmetic results are improved. In adults, most surgeons do not close 5-mm port sites. On the other hand, in children, these sites do present a risk for herniation, and it is advocated that the fascia of a 5-mm port, and even a 3-mm umbilical port, be closed.17,23 There is also an advantage with the radially expanding access system (STEP) trocar entry when compared with standard trocar entry, in terms of trocar site bleeding.21
Other trocars that come with a sharp pyramidal tip can be quite traumatic and may lead to gas leakage and dislodgement. Given the smaller volume of the pediatric abdominal cavity, gas leakage poses a more significant problem than in adult patients. A sharp conical trocar is less traumatic on insertion, because it stretches the tissues, resulting in a smaller opening and tighter fit in the tissues, which minimizes the risks of gas leakage or dislodgement. However, the insertion of such a trocar requires the use of great force that could lead to injuries. Other attempts to decrease gas leakage and slippage have been sandblasted cannulae and cannulae with a screw-like structure. The cannulae with screw- like structures actually enlarge the diameter of the entrance hole. To prevent trocar slippage or dislodgement when placing trocars through very thin abdominal or thoracic walls (eg, in neonates and small children), it is important to secure the trocars with a suture. Despite many innovations in trocar design, none have been able to stay completely stable in this patient population, so some form of additional stabilization is advised.
Sometimes, inserting multiple trocars into the abdomen or chest cavity can create operative space reduction, contact between trocars and instruments, and increase the risk of potential injuries. For these reasons, in little babies it is possible to insert instruments directly into the chest or abdomen through stab incisions, without the use of a trocar.26 This is most useful in cases where there is no need for instrument exchanges, such as in a laparoscopic pyloromyotomy.
Proper instrumentation is the key to successful pediatric MAS. Instruments for adults are frequently too long (32cm to 36cm) and too large in diameter (5mm to10mm) for most children. An adult length instrument, when used for small children, leaves 75% to 80% of the instrument outside of the child and only 20% inside. This leads to awkward manipulation and imprecise movements. The ideal position of endoscopic instruments is to have two-thirds of the instrument inside the body cavity and the other one-third outside of the body to prevent motion parallax. Instrumentation that is shorter (18cm to 22cm) and thinner (2mm to 3.5mm) is now available for pediatric procedures.15,24-27 Similarly, nondisposable trocars that are thin (eg, 3.5mm), short (50mm to 75mm) and can be purchased with or without a gas insufflation port have been developed. The absence of a gas insufflation port on one or more trocars greatly reduces the “footprint” of the collective trocars—this is very helpful when operating on a small neonate.
Telescopes are also available in short, thin sizes. For the small patient, the most commonly used telescope is the 4-mm, 30-degree lens that is 18-cm long.15,24,25 There are telescopes that are as small as 1.2mm, but they have poor light gathering quality, which results in a dim, less colorful picture on the monitor, principally because any telescope ≤2mm in diameter uses fiberoptic, not the superior rod lens, technology. The camera should always be held at the correct angle to the horizon. Angled telescopes can provide different views of the anatomy, which may help clarify structures and maneuvers, especially, suturing and tying. Moving the telescope from one trocar to another for a different view can be a very helpful technique.
The surgeon must also be knowledgeable about the various types of energy sources available and to be able to adjust the energy levels according to the size of the patient. Electrosurgical complications leading to inadvertent burning of adjacent structures is most commonly due to monopolar electrocautery. The noninsulated tip of the cautery device should always be under full endoscopic vision and away from any metal cannula.16,18,24 It is very important to have the whole “active” portion of the instrument visible. It is also a good practice to use the lowest effective settings to avoid collateral damage and arcing potential.
Other devices, such as the ultrasonic scalpel, can generate significant heat on its tips and must also be used with caution. It is important to allow time for the tips of the instrument to cool before grabbing or dissecting bowel. Failure to cool the instrument before dissecting or holding a piece of bowel can result in thermal injury to the bowel and possible delayed perforation.
Pneumoperitoneum causes respiratory and cardiovascular changes in children, which can also lead to complications. Increasing the intraabdominal pressure (IAP) has been shown to modify venous return and systemic vascular resistance. These changes can be significant leading to an arterial pressure increase of 20% to 25%. When the IAP is <10mm Hg, venous return is increased leading to increased cardiac output. However, if the IAP is increased to 20mm Hg, the inferior vena cava becomes compressed, which results in a decrease in venous return and a subsequent decrease in cardiac output.
Similarly, an increase in the IAP to >20mm Hg will also cause a decrease in renal blood flow due to increased renal vascular resistance. It is unclear whether these observations are clinically relevant. An intraabdominal pressure of <15mm Hg appear to be tolerated in otherwise healthy children larger than 5kg, while neonates should be limited to an IAP of ≤12mm Hg.12,19,28,29
Pneumoperitoneum can also lead to displacement of the diaphragm towards the chest leading to a decrease in lung volume. This movement can lead to a reduction in lung compliance and an increase in airway resistance, which leads to an increased risk of barotrauma for the patient.19,28,29 Restricting the mobility of the diaphragm also leads to an uneven distribution of ventilation resulting in a ventilation-perfusion mismatch that can lead to hypercarbia and hypoxia. However, these perturbations can most often be overcome by adjusting the patient’s minute ventilation. The position of the patient can also add to these affects, as respiratory function will be better when the patient is in the reverse Trendelenburg position and more compromised in a steep Trendelenburg position.19
Carbon dioxide insufflation into a body cavity results in variable systemic absorption of the gas that can be managed with appropriate ventilatory techniques. Loss of end-tidal CO2, sudden hypotension, tachycardia, or cardiac arrest may be due to gas embolism into a large vessel. Resuscitative measures, such as positioning the patient with the left side down, a deep Trendelenburg, and aspiration of the right atrium via the central line, may be life saving. Insufflation should be immediately stopped and ACLS measures initiated.
Paralleling the complexity of cases now being performed is the complexity of the room setup, instrumentation, and ancillary equipment. The surgeon should also be trained to appropriately troubleshoot the increasingly complex technology inherent in modern MAS. The xenon bulbs in the light source have a fixed life and should be periodically checked. The amount of gas in the tanks should be checked before every case. Fuses can blow, wires between monitors can become loose or disconnected, and any number of connectors lost or broken. Light and monopolar cords can be mismatched. Not infrequently, the small, delicate telescopes turn up with cracks or bends after processing. The newer instrumentation has handles that are interchangeable and insulating tubes that come off. These can be broken, misplaced, or put together incorrectly. The reusable trocars have valves with fixed life spans, and they can leak as they get older.
SELECT PROCEDURE-SPECIFIC COMPLICATIONS
Problem: Placing the umbilical 12-mm trocar usually requires a lot of energy, making entry injuries more likely.
Solution: Make a small incision on the fascia before inserting the trocar.
Problem: Manipulation injury and iatrogenic perforation of the appendix.
Solution: Use of atraumatic bowel graspers; handle the mesoappendix instead of the distended and friable appendix.
Problem: Poor exposure due to an enlarged liver.
Solution: Place stab incisions higher in both upper quadrants and use the instrument handles as blunt liver retractors.
Problem: Duodenal injury during grasping.
Solution: Use a gentle, full grasp of the duodenum with soft atraumatic graspers. An alternative is to grab the antrum instead of the duodenum for retraction.
Problem: Duodenal perforation during myotomy.
Solution: Use arthroscopy blade with preset cutting depths.
Problem: Serosal tear during muscle spreading.
Solution: Full grasp of the lower or upper edge of the myotomy and spread advancing with both instruments facing each other.
Laparoscopic Nissen Fundoplication
Problem: Thermal injury to the stomach while dividing the short gastric vessels.
Solution: Traction countertraction principle with the help of the assistant and applying the energy source away from the stomach edge.
Problem: Injury to the spleen at the level of the last short gastric vessel.
Solution: Adequate exposure, dissection of a window around the vessel, avoid blunt dissection at this level.
Problem: Pneumothorax during mediastinal dissection.
Solution: Minimal dissection at the hiatus.
Problem: Tight wrap.
Solution: Wide retroesophageal window. The fundus once tunneled to the right side of the esophagus should not retract back when the graspers are released. The stitches should approximate the wrap around the esophagus without tension. Some authors recommend the use of a bougie to avoid narrowing of the distal esophagus.30
Problem: Thick, poorly defined fissure.
Solution: An incomplete fissure can be “completed” using either an endo-GIA stapler (USSC, Norwalk, CT) or the LigaSure vessel-sealing device (Valley lab, Boulder, CO). The stapler is used for large patients, the LigaSure for smaller patients. If there is absolutely no fissure, one must start at the pulmonary artery and trace its course and create a fissure that way.31
Problem: Stenosis or obstruction of the distal airway during bronchus ligation.
Solution: For example, when resecting an upper or right middle lobe, it is recommended that before dividing a bronchus, the bronchus be compressed with a grasper and the lung inflated to make sure that the bronchus going to the lower lobe(s) is not being divided.
Problem: Pulmonary vein or artery branch hemorrhage during ligation.
Solution: When dividing major pulmonary vasculature, loss of control of a vessel can be catastrophic. For this reason, using a device that seals, but does not divide, can help prevent division of a vessel before it is entirely sealed across. This can be performed with the LigaSure, clips, or suture.
Thoracoscopic esophageal atresia with tracheoesophageal fistula repair
Problem: Recurrent laryngeal nerve injury during dissection of the upper pouch.
Solution: Minimize the use of monopolar cautery. Use bipolar cautery. Adequate exposure and identification of the vagus nerve.
Problem: Missing upper pouch fistulae or leaving a large blind pouch when dividing the distal fistula from the trachea
Solution: Identification of the fistula by performing rigid bronchoscopy before starting the operation.
Advanced MAS is rapidly gaining acceptance into the daily practice of pediatric general surgery. Technological advances are moving targets and being able to adapt to different techniques/tools will increase the spectrum of successfully performed pediatric MAS procedures. Safety considerations must be borne in mind as the feasibility of procedures increases. Conversion to an open operation must always be considered when safety is an issue. The surgeon must be aware of the appropriate operating room setting, proper trocar placement, and effects of CO2 insufflation in the abdominal and thoracic cavities. One must know his or her technical limitations and the fact that every procedure has a learning curve that must be overcome to safely perform the operation. The ability to anticipate potential complications will minimize the risk of injuries, because the eyes do not see what the mind does not think.
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