Pneumoperitoneum: Physiologic effects

Laparoscopic surgery requires the insufflation of the abdominal cavity for visualization and working space. The most common gas used for insufflation is CO₂ because it is colorless, non-flammable, and non-toxic. Insufflation is usually maintained at an intra-abdominal pressure (IAP) between 10-15 mmHg (normal <5mmHg). The physiologic effects of insufflation are the result of an increase in intra-abdominal pressure (IAP) and the systemic absorption of CO₂.

Respiratory Effects:

The pulmonary effects of insufflation mainly relate to the increase in IAP. Pneumoperitoneum displaces the diaphragm cephalad causing a decrease in functional residual capacity (FRC). This results in airway collapse, atelectasis, and V/Q mismatch. A mild respiratory acidosis is frequently observed. Trendelenburg positioning can further potentiate the decrease in FRC.

Cardiovascular Effects:

Pneumoperitoneum can result in significant hemodynamic derangement. During insufflation, venous return (VR) to the heart is decreased secondary to compression of the inferior vena cava (IVC). Systemic vascular resistance (SVR) is typically elevated as a result of catecholamine release and direct effects of increased IAP. Thus, cardiac output can be as much as 30% decreased due to increased afterload and decreased preload. Patients with cardiac disease or hypovolemia are more prone to these affects.

Renal Effects:

Insufflation results in decreased renal blood flow (RBF) and increased vascular resistance leading to decreased GFR. These effects are temporary.

Gastrointestinal:

Insufflation may lead to an increased risk of regurgitation and aspiration of gastric contents.