Instruments for the NOTES toolbox
• Single-channel therapeutic endoscope
• Needle knife papillotome
• 450-cm Jagwire
• 18–20 mm wire-guided balloon dilation catheter
• Standard electrosurgical generator
Fig. 14.1
Picture of Jagwire passing through the pinpoint gastrotomy made with needle knife. This flexible wire is used to facilitate balloon placement for dilation of the gastrotomy
Fig. 14.2
Radially dilating balloon enlarging gastrotomy to accommodate transgastric passage of endoscope
Fig. 14.3
Transgastric passage endoscope through the endoscopically created gastrotomy
It should be noted that the aforementioned technique was described in a population that was undergoing a procedure that would otherwise necessitate a gastrotomy secondary to the lack of safe options for reliable endoscopic closure during an elective gastrotomy. While not completed in a human population, Pauli et al. described the creation of a submucosal tunnel for transgastric access similar to what is performed during a POEM [23]. Their self-approximating transluminal access technique, or STAT, employs principles of endoscopic submucosal resection. The procedure begins with the injection of 10 mL of saline into the gastric submucosa. Using a needle knife, a 1–1.5-cm incision is made in the mucosa. Submucosal dissection is then completed with the assistance of a grasping forceps for a total of 10–12 cm. Having achieved an appropriately long tunnel, the needle knife is again used to breach the muscular wall of the stomach. Similar to the technique used by Nau et al. [21], a radial dilating balloon is then used to create a gastrotomy large enough to accommodate the endoscope. The mucosal defect is closed with endoscopic clips and the seromuscular incision is left alone. While of uncertain clinical significance, it is notable that there were infections found in 40% of the animals on necropsy following a two-week survival period (one microabscess and one submucosal abscess). Given that Khashab et al. have recently described a per-oral endoscopic pyloromyotomy in a human patient and the submucosal tunnel is routinely used for the POEM, this description may likely be a reasonable approach to accessing the peritoneal cavity [24].
The transgastric approach to the peritoneal cavity is ideal in that it affords the surgeon unhindered access to many of the structures within the abdomen. The muscular wall of the stomach is also well suited to resist the shearing forces associated with a transgastric procedure. Gastrotomy positioning is reliable and safe. To date, however, there is no safe and reliable method for gastrotomy closure. Certainly the technique described by Pauli et al. [23] and the successes of the POEM procedure suggest that a tunneling technique may be a reasonable alternative to accessing the abdominal wall directly. Given the morbidity and mortality of a gastric leak, however, this aspect of the transgastric procedure must be consistent and safe prior to offering the approach to a population that does not otherwise need a gastrotomy.
Insufflation of the Abdominal Cavity
With the introduction and widespread adoption of laparoscopy as a viable approach to treating abdominal pathology, a new collection of issues arose. Principle among those was the technique for insufflating the abdomen and the physiologic consequences associated with this act. The cardiopulmonary implications of pneumoperitoneum established using laparoscopic techniques are well established [25–28]. Peritoneal insufflation to a pressure of more than 15 mm Hg may affect increases in aortic pressure, decreased urine blood flow and a respiratory acidosis secondary to systemic carbon dioxide absorption. With that said, laparoscopic surgery can be safely completed utilizing modern anesthetic techniques even in critically ill patients [29]. Establishing the safety and efficacy of the endoscopic creation of pneumoperitoneum is necessary if the NOTES approach is to be validated.
Initial studies completed in animal models replicated the techniques utilized for standard laparoscopy. Using a Veress needle, Ko et al. were able to access and insufflate the abdominal cavity allowing for effective gastrotomy creation for a diagnostic peritoneoscopy in a swine model [10]. This practice was replicated in the initial human series at the Ohio State University, safely and effectively establishing pneumoperitoneum with classic laparoscopic techniques, allowing for a natural orifice procedure [19].
In an effort to assess for a stand-alone NOTES procedure, von Delius et al. evaluated the effect of pneumoperitoneum established using the on-demand endoscopic air pump [30]. Using a swine model, they noted a wide variation in the intra-abdominal pressures with maximal pressures of 22 mm Hg and pressures greater than 15 mm Hg in 21% of the measurements. Meireles et al. witnessed similar results when comparing laparoscopic insufflation to on-demand endoscopic insufflation, again noting elevated intra-abdominal pressures in the endoscopic cohort with values exceeding 30 mm Hg [31]. It is with this deficiency in mind that the group from the Ohio State University assessed for the accuracy and safety of insufflating the abdomen using a hybrid technique [32]. To complete this investigation, the authors obtained blind peritoneal access as described above. Next, the laparoscopic insufflator was connected to the therapeutic channel of the endoscope and the abdomen insufflated to a pressure of 10 mm Hg. The pressure reading was then verified by connecting the insufflator to a Veress needle passed through the left upper quadrant. In a population of twenty patients, the authors noted that the mean pressure reading was 9.8 mm Hg (range 5–17 mm Hg) through the endoscope and 9.8 mm Hg through the Veress needle (range 4–17 mm Hg). This difference was not statistically significant (P = 0.9) and the absolute mean pressure difference between the 2 methods on a case-by-case basis was only 1.0 mm Hg.
Given the well-established deleterious effects of pneumoperitoneum on the cardiopulmonary and renal systems, the establishment of responsible methods for insufflating the abdominal cavity is critical to the success of NOTES. There is excellent literature supporting laparoscopy in critically ill cardiac patients. It stands to reason that the same technology utilized from a NOTES platform would have a similar safety profile. It is with that premise that the use of the laparoscopic insufflator through the working channel of the endoscope was validated as safe technique for establishing pneumoperitoneum in a NOTES procedure.
Infectious Implications
Critical to the validation of natural orifice approach is the establishment of the safety and efficacy of the technique. Flexible endoscopy as a diagnostic and therapeutic modality is well established from an intra-luminal approach. Traversing the gastric wall presents a new set of risks, including the risk of cross-contamination of the abdominal cavity with gastric flora. The gastric milieu is necessarily contaminated, and the risk that this poses to the patient must be negligible in order for a transgastric NOTES to be a viable option.
The question of the infectious implications of a transgastric procedure has been addressed from numerous different viewpoints using animal models. McGee et al. investigated the systemic inflammatory response of a transgastric procedure using pigs [33]. This group evaluated for changes in markers for inflammation including TNF-α and IL-6 following different interventions. They noted that systemic inflammation was similar when comparing a NOTES population to one undergoing both an exploratory laparotomy as well as exploratory laparoscopy.
Others have attempted to address the question of whether some degree of gastric decontamination is necessary to prevent cross-contamination of the peritoneal cavity with gastric flora. Again employing pigs, Eickhoff investigated a complex gastric decontamination protocol versus only gastric irrigation [34]. The authors found a statistically significant increase in the intra-abdominal bacterial burden in the control population. Perhaps more significant, however, was the finding that there was no difference in the rate of microscopic or macroscopic peritonitis between the two groups. McGee et al. also found no difference in the number of positive peritoneal cultures or intra-abdominal infections when comparing gastric lavage to an antibiotic-enriched lavage [35]. Contrasting this, Giday et al. noted a significant increase in both the number of abscesses as well as positive peritoneal cultures following a transgastric procedure without pre-procedural decontamination [36]. While it is clear that the gastric effluent is contaminated, there is no definitive information on the infectious implications in the animal studies to date.
It is with this ambiguity in mind that the Ohio State group investigated that infectious burden of a transgastric procedure in a human population. In each case, a single intravenous dose of preoperative prophylactic antibiotics was administered. No irrigation or decontamination of the stomach was completed. The endoscope was cleaned with glutaraldehyde per a standardized protocol, but was not considered sterile. The initial study completed assessed the infectious risks associated with the creation of a gastrotomy or jejunotomy during a laparoscopic Roux-en-Y gastric bypass (RYGB) [37]. Aspirates were collected from the stomach, from the peritoneum prior to violation of the intestines, and from the same location after completion of the operation. In this experiment, they found five of twenty possible cases of cross-contamination defined by similar bacterial isolates from the stomach found in the peritoneal samples. Most importantly, they identified no iatrogenic infections in any patient enrolled.
In the second experiment, the degree of contamination of the scope and the role of transgastric passage of this device was evaluated [21]. To do this, cultures were taken from sterile washes of the scope prior to the procedure, and then, cultures were drawn from the peritoneal cavity prior to, and following, transgastric passage of the endoscope. In this cohort, they found no difference in the bacterial burden following the gastrotomy, nor did they identify any instances of cross-contamination of the peritoneal cavity with gastric flora. In their final experiment, they evaluated the infectious risks of a stand-alone NOTES procedure via cultures taken from the stomach and then again from the peritoneal cavity after transgastric passage of the endoscope [38]. In each case, the cultures were collected by completing sterile washes through the therapeutic channel of the endoscope. In this study, the median level of bacteria present was significantly higher in the gastric samples (980 vs. 320 CFU/ml, p = 0.001). Cross-contamination from the stomach to the peritoneal cavity was documented in 21% of the cases. Interestingly, there was a higher bacterial burden in the stomach in those patients on proton pump inhibitors (PPI’s) (n = 25) (7,800,000 vs. 340 CFU/ml; p = 0.01). However, in no instance was there an infectious complication noted in either the group using PPI’s or the group as a whole.
This question is the crux of the issue of infectious implications of a transgastric operation. Inherent in any procedure that violates the gastrointestinal tract is the potential for translocation of intra-luminal bacteria to the peritoneal cavity. It is the clinical significance of this translocation that must be considered rather than the absolute bacterial load or cross-contamination of species. The work by Hazey et al. [19] has shown that this risk is minimal and should not deter the development of this approach.
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