Laparoscopy and the ever-expanding robotic-assisted techniques have revolutionized the field of minimally invasive surgeries. Pneumoperitoneum is the keystone that allows surgeon to create a visual field and working space necessary to conduct the operations. A basic understanding of the pneumoperitoneum process and its fundamental components is essential to create a safe and effective operating environment.
Indications and Contraindications
Pneumoperitoneum is an essential component in any transperitoneal laparoscopic surgery. Instillation of gas into the peritoneum allows distention of a potential space to safely visualize and manipulate tissues. It is a prerequisite for any contemporary transperitoneal laparoscopic or robotic surgery and hence indicated for any such procedure. Conversely, contraindications to laparoscopic surgery disqualify establishment of pneumoperitoneum. Uncorrectable coagulopathy, hypercapnia, intestinal obstructions, limiting working space, significant abdominal wall infections, hemoperitoneum or hemoretroperitoneum, generalized peritonitis, and suspected malignant ascites may preclude establishment of pneumoperitoneum.
Fundamental to the development of adequate pneumoperitoneum is proper access to the peritoneal cavity. Clearly, without proper access, pneumoperitoneum may not be feasible. Ports and establishing access are discussed elsewhere in the text. Nonetheless, intra-abdominal adhesions from prior operations or inflammatory processes can increase the risk of inadvertent injury to the surrounding structures and make safe pneumoperitoneum difficult. Additional limiting factors include presence of abdominal mesh, cirrhosis, portal hypertension, morbid obesity, pelvic fibrosis, organomegaly, pregnancy, hernias, and vascular aneurysms, although recent evidence suggests improved safety.
Of equal importance to the aforementioned patient-related factors are the surgical team elements. Clear understanding of the physiologic implications of pneumoperitoneum by the anesthesiologist and surgeon are critical. Furthermore, 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 is important when selecting candidates for a laparoscopic or robotic-assisted approach. For any complications related to access, pneumoperitoneum, or laparoscopic surgery to be minimized, a careful patient history and physical examination should be conducted. Inquiries should focus on the patient’s medical conditions and prior surgical history including previous surgical approach, intraoperative or postoperative abdominal complications, and wound infections. The physical examination should also encompass an assessment of body habitus, presence of prior surgical scars, and abdominal hernias. Patients with chronic obstructive pulmonary disease (COPD) may benefit from baseline quantification of disease severity through arterial blood gas and pulmonary function testing. Instead of carbon dioxide (CO 2 ), nitrous oxide or helium gas may be used for insufflation in patients who are intolerant to hypercapnia and subsequent acidosis.
Operating Room Configuration
The operating room should be set up in a manner that maximizes surgical safety and efficiency of the task at hand. Specific floor diagrams for personnel and equipment will be procedure specific and are discussed elsewhere in this textbook. In general, all necessary equipment should be present in the operating room and tested to ensure proper functioning. The insufflator 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 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 tested to confirm its safety mechanisms.
Specific techniques for establishing pneumoperitoneum are covered in greater detail elsewhere in this textbook. In brief, pneumoperitoneum can be initiated using open access techniques (Hasson technique, or through a hand port incision) as well as closed access techniques (Veress needle). Optimal 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 fingerbreadths superior and medial to the anterior superior iliac spine. A Veress needle can also be used to confirm the absence of underlying adhesions by inserting it into an insufflated abdomen at an intended trocar site.
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 intra-abdominal pressure during laparoscopy. A variety of vendors offer insufflation systems ( Table 8-1 ). 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. 8-1 ).
| Manufacturer | Product | Maximum Flow Rate |
|---|---|---|
| Karl 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 CO2 Insufflator | 40 L/min |
Initial insufflation of the abdomen should be started at a slow rate (1-2 L/min). Rapid rates risk rapid stretching of the peritoneum, which may precipitate cardiovascular dysfunction, such as hypotension, bradycardia, arrhythmia, and rarely cardiac arrest. In such circumstances, the pneumoperitoneum should be immediately released, followed by cardiopulmonary resuscitative measures. After clinical stabilization and if appropriate, pneumoperitoneum may be reattempted with slow insufflation followed by maintenance of intra-abdominal pressures below 12 to 15 mm Hg.
During pneumoperitoneum, any leakage through the trocar or abdominal wall is sensed by the insufflator unit and compensated for by increased reinsufflation of the gas volume to maintain a preset intra-abdominal pressure. The patient should remain adequately anesthetized because abdominal wall contractions during pneumoperitoneum can unexpectedly increase intra-abdominal 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 because of greater resistance exerted by a thick abdominal wall as well as frequent instrument changes. For such patients, high–flow rate insufflators may be better suited because 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, during constant smoke evacuation, or during instances of a dislodged port cannula.
During high–flow rate settings, the intra-abdominal pressure will quickly rise to maintain a constant velocity. High-flow insufflators commonly use the overpressure insufflation principle, resulting in intermittent high peak intra-abdominal 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 require low resistance in the insufflation system.
Tubing Equipment
Insufflation gas is carried toward the trocar port via flexible tubing. Typically, it houses a disposable 0.3-micron gas filter to prevent any contaminants from entering the insufflator and gas storage cylinder. Before pneumoperitoneum is initiated, the tubing toward the patient should be purged of 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 the Hagen-Poiseuille law :
Φ = π × r 4 8 × η × l × Δ P
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