Insufflators and the pneumoperitoneum

Indications and contraindications

Pneumoperitoneum is an essential component in any transperitoneal laparoscopic or robotic-assisted surgery. Instillation of gas into the peritoneum allows distention of the peritoneal space to safely visualize and manipulate tissues. Consequently, it remains a prerequisite for virtually all minimally invasive procedures. Conversely, contraindications to laparoscopic surgery disqualify establishment of pneumoperitoneum. Uncorrectable coagulopathy, hypercapnia, intestinal obstructions limiting working space, significant abdominal wall infections, hemoperitoneum, generalized peritonitis, and malignant ascites may preclude establishment of such pneumoperitoneum.

Ensuring safe and effective access to the peritoneal cavity is a fundamental aspect of establishing pneumoperitoneum. Intraabdominal adhesions, often from prior surgeries or inflammatory processes, can increase the risk of inadvertent injury to the surrounding structures when placing ports or establishing access into the peritoneal cavity. Additional limiting factors include the presence of abdominal mesh, cirrhosis, portal hypertension, morbid obesity, pelvic fibrosis, organomegaly, pregnancy, hernias, and vascular aneurysms, though recent evidence suggests improved safety. ,

Of equal importance to the abovementioned patient related factors are the surgical team elements. Clear understanding of the physiologic implications of pneumoperitoneum by the anesthesiologist and surgeon is critical. Further, proper operative equipment should be readily available, along with trained ancillary staff members, for troubleshooting common equipment malfunctions.

Patient preoperative evaluation and preparation

Careful preoperative assessment of patient comorbidity status informs the selection of candidates for laparoscopic and/or robotic surgery. To minimize complications related to the mechanics of establishing pneumoperitoneum and performing a minimally invasive procedure, surgeons should conduct a thorough patient history and physical examination. Inquiries should focus on patient’s medical comorbidities, performance status, and surgical history. Regarding surgical history, details pertaining to surgical approach, operative complications, and wound complications are critical. Physical examination should note body habitus, surgical scars (location and number), and any hernias. Patients with cardiopulmonary disease may benefit from preoperative risk stratification and functional testing. Those more sensitive to hypercapnia, often due to pulmonary disease, may require nitrous oxide or helium for insufflation rather than carbon dioxide.

Operating room setup

In conjunction with anesthesia, the surgery team should organize the operating room to maximize surgical safety and efficiency. Specific floor diagrams for personnel and equipment are procedure-specific and are discussed elsewhere in this textbook. With regards to insufflation, the insufflator apparatus must be in clear view for the surgical team to monitor pressures at the beginning of the case and as needed during the case. It is important to check for readiness of the suction-irrigator unit and an adequate insufflation gas supply. The insufflator unit should be checked for its preset settings, tubing equipment, and presence of gas flow. Furthermore, its alarms should be prompted to confirm its safety mechanisms.

Specific techniques of establishing pneumoperitoneum have been covered in greater detail elsewhere in this textbook. In brief, pneumoperitoneum can be initiated using open access techniques (Hasson or through a hand port incision) as well as closed access techniques (Veress needle). Preferred access points for Veress needle access include the umbilicus, Palmer’s point (midclavicular line subcostal, 3 cm inferior to the costal margin), and a site two fingerbreadth superior and medial to anterior superior iliac spine. A Veress needle can also be utilized to confirm the absence of underlying adhesions by inserting it into an insufflated abdomen at an intended trocar site. After puncture with the Veress needle, drawing back on the attached syringe and the drop test can further confirm a safe entry point, avoiding bowel or blood vessels.

Components of the insufflation system

Insufflator unit

An understanding of the insufflator system design and features is helpful for any laparoscopic surgeon. There are three components to the insufflation system: insufflator, tubing equipment, and insufflation gas. The role of an insufflator unit is to establish, monitor, and maintain a constant intraabdominal pressure during laparoscopy. There are a variety of vendors who offer insufflation systems ( Table 9.1 ). Displayed on the face of the unit are modifiable settings for pressure and flow, alarm alerts, and real-time values for pressure, flow, and volume instilled ( Fig. 9.1 ).


Examples of Laparoscopic Insufflators

Manufacturer Product Maximum Flow Rate
Storz Thermoflator, Endoflator 20–50 L/min
Olympus UHI-4 45 L/min
SurgiQuest AirSeal iFS System 40 L/min
Stryker 45L PneumoSure insufflator 45 L/min
Wolf Laparoscopic CO 2 insufflator 40 L/min

Fig. 9.1

Examples of insufflator units and their control inputs. A, Karl Storz Thermoflator with display and heating element. B, Olympus UHI-4.

(A © 2021. Photo courtesy KARL STORZ GmbH & Co. KG. B Courtesy Olympus America, Center Valley, PA)

Initial insufflation of the abdomen should begin at a slow rate (1–2 L/min). Faster rates risk rapid stretching of the peritoneum, which may precipitate cardiovascular instability, such as hypotension, bradycardia, arrhythmia, and rarely cardiac arrest. In such circumstances, the pneumoperitoneum should be immediately released followed by cardiopulmonary resuscitative measures. Following clinical stabilization—and if appropriate—pneumoperitoneum may be reattempted with slow insufflation followed by maintenance of intraabdominal pressures below 12–15 mm Hg.

During pneumoperitoneum, any leakage through the trocar or abdominal wall is sensed by the insufflator unit and compensated by reinsufflating the gas volume to maintain a preset intraabdominal pressure. The patient should remain adequately anesthetized as abdominal wall contractions during pneumoperitoneum can unexpectedly increase intraabdominal pressure up to 50 mm Hg. , Similarly, leaning on the patient’s abdomen or placing heavy equipment can trigger automatic insufflator shutoff followed by pressure loss and time delay.

In obese patients, maintaining a stable pneumoperitoneum becomes more critical due to greater resistance exerted by a thick abdominal wall as well as frequent instrument changes. For such cases, high flow rate insufflators may be better suited as they can deliver rapid insufflation of the lost gas volume. High flow rates can also help maintain pneumoperitoneum in emergent circumstances such as during bleeding requiring aggressive suctioning, constant smoke evacuation, or instances of dislodged port cannula.

During high flow rate settings, the intraabdominal pressure will quickly rise to maintain a constant velocity. High flow insufflators commonly employ the overpressure insufflation principle resulting in intermittent high peak intraabdominal pressures during periods of insufflation despite a lower preset value. An advantage of this approach is rapid establishment of pneumoperitoneum. However, higher intermittent abdominal pressures and repeated peritoneal stretching may stimulate vagal responses leading to various clinical sequelae. Low-pressure principle insufflators do not exceed the preset value, but they require low resistance in the insufflation system.

Tubing equipment

Insufflation gas is carried toward the trocar port via flexible tubing. Typically, the tubing houses a disposable 0.3-µm gas filter to prevent any contaminants from the insufflator and gas storage cylinder. Prior to initiating pneumoperitoneum, the tubing towards the patient should be purged of the room air to reduce the risk of mixed air gas embolism. ,

An important concept is that of resistance within the entire insufflation system. Minimizing the resistance of the system is perhaps of greater clinical significance than investing in costly high flow insufflation units. Principles of gas flow have been described by Hagen-Poiseuille’s law.

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Aug 8, 2022 | Posted by in UROLOGY | Comments Off on Insufflators and the pneumoperitoneum

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