Laparoscopic bariatric surgery cannula placement and open approach techniques
Once the pressure reaches 15 mmHg, the trocar cannula can be inserted through the first puncture port. The surgeon should operate in a comfortable position to avoid excessive displacement of the trocar cannula. Methods to reduce complications include raising the operating table to waist height, using a shorter trocar cannula, and having the surgeon support the cannula with their other hand to prevent excessive insertion.
The placement of a trocar directly at the umbilicus without pneumoperitoneum is similar to the method described above for placing a pneumoperitoneum needle. Precise positioning and a puncture trajectory downwards from the midline are emphasized. Most studies, including large meta-analyses, report a complication rate similar to that using a pneumoperitoneum needle (0.3%). An alternative is a long, conical trocar with fascial dilatation properties, which can lift the rectus abdominis sheath during puncture to create negative intra-abdominal pressure (45 cadaveric studies). This is similar to another spiral device recently described for use in obese patients.
Another type of direct-viewing instrument system allows real-time visualization of the first puncture sheath's channel, regardless of whether pneumoperitoneum is present. One instrument (Visiport, US Surgical, Norwalk, CT, USA) uses a sharp cannula to puncture each layer; the other instrument (Endopath Xcel, Ethicon Endo-Surgery, Cincinnati, OH, USA) uses a transparent, cone-shaped, blunt cannula. Because both cannulas are transparent, the condition of each layer of abdominal wall tissue can be visualized during puncture. Theoretically, this instrument helps avoid injury. Early clinical observations also suggested it could reduce the incidence of complications. However, a retrospective analysis of a nationwide clinical database revealed that this instrument caused a higher complication rate. From 1994 to 2000, there were 79 cases of serious complications, 37 cases of major vascular injury, and 4 deaths. Meta-analysis revealed a trend that in routine surgery, the use of instruments for abdominal paracentesis (including the use of pneumoperitoneum needles) to enter the abdominal cavity results in more complications compared to open access to the abdominal cavity.
**Open access to the abdominal cavity**
Hasson et al. reported complications that can occur with pneumoperitoneum needles, and therefore suggested an "open" approach with a 1-1.5 cm incision at the umbilicus to expose the fascia and peritoneum under direct vision. A blunt obturator cannula is inserted directly into the abdominal cavity, followed by suturing the fascia to close the incision and fixing the cannula. Its advantages are a significantly reduced (but not eliminated) risk of aortic injury and faster establishment of pneumoperitoneum and access to the abdominal cavity; its disadvantages are the extreme difficulty in exposing obese patients, higher operative complexity, and a slightly higher risk of intestinal injury. Furthermore, maintaining a leak-free gas supply around the cannula is a challenge in severely morbidly obese patients. This study may have case selection bias, as this method is more often used for repeat surgeries and when other techniques are also expected to fail to achieve successful access to the abdominal cavity. The operative time for this method is comparable to that using pneumoperitoneum needles.
Another modified Hasson technique involves making a small, open incision through the umbilicus using a 5mm blunt trocar under direct vision. This technique does not involve sutures to fix the fascia and is recommended for patients without other abdominal complications or complexities; its applicability is limited in patients with morbid obesity. Senapati et al. described a semi-open modified Hasson technique by opening the linea alba and entering the peritoneum through a blunt conical trocar. Only one case of minor liver injury was reported among 241 patients treated with this method. Balloon-shaped blunt trocars are widely used in inguinal hernia repair and are beginning to be used in abdominal surgery, but funding factors may limit their widespread application.
**Abdominal Assessment**
Regardless of the method of entry into the abdominal cavity, the abdomen should be checked for accidental injury before inserting the laparoscope, especially the mesentery, greater omentum, retroperitoneum, abdominal wall, and adjacent bowel segments. If hypotension, bradycardia, or inability to ventilate normally occurs, the abdomen should be emptied immediately. The laparoscope should be used rapidly and repeatedly to carefully examine for vascular injury under low intra-abdominal pressure. If unexplained hypotension persists, conversion to open surgery should be considered for more thorough exploration of the retroperitoneal tissue. Maintain high vigilance at all times to avoid injury to major blood vessels and bleeding.
**Installation of other cannulas**
After the first cannula enters the abdominal cavity, multiple entry points for instruments need to be placed on the abdominal wall. Commonly used cannulas include conical cannulas, retractable cannulas, cutting cannulas, conical cannulas, and radially retractable cannulas. All instruments should always be inserted into the abdominal cavity through the abdominal wall under laparoscopic visualization. Cannulas of different lengths can be selected depending on the thickness of the abdominal wall. Due to the thick subcutaneous fat tissue in morbidly obese patients, the freedom of movement under surgical visualization may be limited. The use of specific instrument sets should be carefully considered, and the cannula angle should maximize the required freedom of movement. This requires considerable experience and is a challenging aspect of the early learning stages of bariatric surgery.
Different types of cannulas have their own advantages and disadvantages. Radial retractable cannulas cause less pain due to less damage to the fascia and muscles. Threaded puncture screws (EndoTIP, Karl Storz Endoscopy America, Culver City, CA, USA) use lateral expansion force instead of axial force and employ a tapered puncture sheath, thus reducing the incidence of abdominal wall vascular injury. The "safety" gate design of cutting cannulas has not reduced the injury rate; according to the US FDA, there were 408 serious injuries from 1993 to 1996, although this number is much lower than the total reported in medical literature.