Hopkins rod-lens optical system.
Challenges and Hurdles
The delay in the development of minimally invasive pediatric surgery can be attributed to many factors. There have been many financial constraints. Equipping hospitals with adequate pediatric laparoscopic operating room equipment and staff training is costly . Initial operative times were longer with MIS approaches, also increasing costs . Furthermore, with pediatric open surgery compared to adult, the cosmesis and length of stay are generally better thus requiring an even greater final margin from the MIS approach .
In addition to the financial hurdles , a new skill set is needed which includes depth perception, tactile sensation, and operative choreography . New methods of teaching are required for the intricate details of minimally invasive surgery. Surgical instruments that were used for adult surgeries were too large and hazardous when used in infants and children (Fig. 2.2) . Once the surgical instruments decreased in size and safe endoscopic techniques were discovered, pediatric surgeons were more apt to apply thoracoscopy and laparoscopy to neonates.
Originally designed adult laparoscopic instruments were too large and hazardous for pediatric surgical use. From Georgeson K. Minimally invasive surgery in neonates. Semin Neonatol. 2003 Jun;8(3):243–8. Reprinted with permission from Elsevier Limited.
Types and Sizes
There are several commercially available trocar types including the MiniSite system by Covidien, the 3-mm minilaparoscopy set from Storz, the Aesculap Reusable Trocar System, and the Passport trocars from Stryker. The important tenants are safe insertion and ease of instrument exchange. Some trocars, like the MiniSite system , are inserted with a spring-loaded, blunt stylet (Fig. 2.3) or contain a metal conical tipped trocar like the Storz system. Each patient and case is unique; the trocar location and selection are specific to the size of the patient, the instruments being used, and the discretion of the surgeon . Trocar sizes have been a challenge from the onset of minimally invasive surgery in pediatrics. The decrease from 5- and 10-mm instrumentation to 2- and 3-mm instrumentation has greatly aided surgeons in the complicated procedures of their smaller patients. Procedures became feasible in the littlest of children. In general, incisions and trocars are between 2 and 4 mm for neonates. Incisions less than 2 mm heal well without visible scarring. With trocars smaller than 4 mm, a red catheter sleeve can be fit around the outside of the trocar to help stabilize the trocar. The catheter sleeve can then be sutured to the skin thus allowing the trocar mobility without slippage . An example is the two-piece sealing cap that fits at the end of the cannula of Aesculap trocars to preserve the pneumoperitoneum and prevent inadvertent removal when sutured to the abdominal wall. For the more traditional system, the Storz system contains silicone leaflet valves to maintain pneumoperitoneum.
The MiniSite system is inserted with a spring-loaded, blunt stylet. From Krpata, D.M. and T.A. Ponsky, Needlescopic surgery: what’s in the toolbox? Surg Endosc, 2013. 27(3): p. 1040–4. Reprinted with permission from Springer.
The most common injuries from trocars include bleeding, hernias, bowel injuries, and bladder injuries . The abdominal wall of neonates is relatively thin which allows for slippage of the trocars when instruments are placed through them . Trocar instability can cause a gamut of complications, including air leakage, loss of vision, instrument clashing, and others . Rothenberg reports a specific complication directly related to the laparoscopic approach during one of his procedures: the “injury was a bladder wall injury secondary to the replacement of a 3 mm trocar in the suprapubic position after it had slipped out. The injury was extraperitoneal and was managed by Foley catheter drainage for 5 days” . Jayaram et al. describe an efficient way to prevent complications from trocar instability with the use of a 16- or 18-Fr Foley catheter sleeve over the trocar, in which the sleeve is then fixed to the skin with a stitch . In addition, major vascular injury can occur with trocar insertion including iliac, caval, and umbilical vein injury .
Smaller and more versatile instruments have greatly expanded the laparoscopic capabilities in neonates. Figure 2.4 demonstrates the comparison between 3- and 5-mm instruments. A reliable and versatile set of reusable instruments for pediatric laparoscopy is essential for success. The 3-mm minilaparoscopy system by Storz has a set with 36-cm-long instruments that include graspers, dissectors, scissors, cautery, suction, and needle holders for intracorporeal suturing (Fig. 2.5). The major advantage of this set is that it is the only 3-mm set that offers a 36-cm length which is helpful for pediatric patients with thicker abdominal walls. In addition Storz offers this set in 20- and 30-cm lengths. Other brands include Stryker which offers 3-mm instruments and Sovereign® mini-instruments (Aesculap, Center Valley, PA) which makes 3.5-mm instruments. Finally the MiniSite™ system makes 2-mm instruments that can be used directly through the abdominal wall or through a specially designed part .
Comparison between 3- and 5-mm instruments. From Krpata, D.M. and T.A. Ponsky, Needlescopic surgery: what’s in the toolbox? Surg Endosc, 2013. 27(3): p. 1040–4. Reprinted with permission from Springer.
The 3-mm minilaparoscopy system by Storz. From Krpata, D.M. and T.A. Ponsky, Needlescopic surgery: what’s in the toolbox? Surg Endosc, 2013. 27(3): p. 1040–4. Reprinted with permission from Springer.
Insufflation Pressure and Physiology
Respiratory parameters are affected due to the insufflation pressures, the CO2 absorption, and the position of the patient. Pediatric patients have a higher oxygen consumption, minute ventilation, and airway resistance than adults. Pediatric patients have a lower functional residual capacity (FRC) (10 % of total lung capacity) and high closing volume compared with adults . The low FRC causes a ventilation-perfusion mismatch and alveolar dead space that is further exaggerated during laparoscopic surgery. During laparoscopic surgery, the diaphragm is displaced upward due to the insufflation force, resulting in a reduction of the lung volume and creating a ventilation-perfusion mismatch. Stiffening of the chest wall due to abdominal distention and impaired diaphragmatic motion also restricts lung expansion. Gas exchange is affected more severely in infants than adults due to these physiologic reasons . There is a linear correlation with the changes in respiratory function and the intraperitoneal pressure. Due to the stepwise design of the study performed by Bannister et al., they discovered that significant pulmonary changes occur at a pressure of 10 mmHg and greater .
Carbon dioxide (CO2 ) insufflation in the pediatric population can result in hypercarbia secondary to CO2 absorption, changes in respiratory function, and cardiac output and acidosis . Hypercarbia and increased intra-abdominal pressures can cause increased intracranial pressures and cerebral hemorrhage. Cardiovascular parameters are also affected during laparoscopic surgery. At baseline, infants and neonates have a relatively higher cardiac index and oxygen consumption than adults. The mean arterial pressure is lower, and the central venous pressure is comparable . Cardiac output decreases when intra-abdominal pressure exceeds 20 mmHg and when blood flow to the heart is obstructed via compression of the inferior vena cava from cardiac compression to reduction in end-diastolic volume, respectively. Increased intra-abdominal pressures above 10 mmHg can compromise venous return due to compression of the inferior vena cava thus causing hypotension . Systemic vascular resistance is increased due to compression of the aorta and increase in splanchnic arteriolar vasoconstriction from an increased intra-abdominal pressure . Neonates are especially sensitive to absorption of CO2, causing hypercapnia and hypoxia, and can develop respiratory acidosis.
The main physiological changes upon insufflation are an increase in end-tidal CO2 and an elevation in peak airway pressures which can be compensated for with slight hyperventilation. Intraoperative minute ventilation should be increased to maintain normocapnia , and care should be taken to monitor the neonates that are at risk postoperatively of not being able to maintain increased respiratory rate to blow off the remaining CO2 . Patients should be monitored with electrocardiogram, pulse oximeter, and end-tidal CO2 monitor, because at pressure 12–14 mmHg, liver and kidney perfusion is decreased. The insufflation pressure should be set at the lowest possible pressure giving the best possible exposure without causing harm .
The very first entirely thoracoscopic repair of a tracheoesophageal fistula was done in 1999, and it described a repair of pure esophageal atresia in a 3.4-kg 8-month-old infant . Since then there have been numerous successfully performed thoracoscopic esophageal atresia repairs since the operation is easier on the patient, requires less dissection than open repair, and provides better visualization of the field. Thoracoscopic procedures require main stem intubation of the opposite lung to provide single-lung ventilation and low-flow, low CO2 to help collapse the lung on the involved side. Single-lung ventilation is required because double-lumen tubes are not available in sizes small enough to accommodate the airway of a neonate. Insufflation with CO2 into the pleural space can also help create a larger intrathoracic working space and improve exposure and visualization by pushing the diaphragm down. CO2 may cause less pulmonary compromise during the operation when compared to standard mechanical retraction .