What physiologic alteration results in compression of the inferior vena cava (IVC) during insufflation?

From the Guidelines

Increased intra-abdominal pressure during insufflation for laparoscopic procedures directly compresses the inferior vena cava, reducing venous return to the heart. This compression occurs when carbon dioxide gas is introduced into the peritoneal cavity to create pneumoperitoneum, typically at pressures of 12-15 mmHg 1. The mechanical pressure on the vena cava decreases preload to the heart, potentially reducing cardiac output and causing hypotension. This effect is more pronounced when patients are placed in Trendelenburg position (head down), which further increases intra-abdominal pressure on the vena cava. Some key points to consider include:

• The physiologic consequence is decreased venous return from the lower extremities, resulting in blood pooling in the legs and reduced central venous pressure.
• Anesthesiologists must monitor for these hemodynamic changes during laparoscopic procedures and may need to adjust fluid management or vasopressor support to maintain adequate blood pressure and tissue perfusion.
• The compression effect is generally reversible once the pneumoperitoneum is released at the end of the procedure.
• It is also worth noting that the growing fetus in pregnant women can result in upward pressure on the diaphragm and downward pressure on the pelvic floor, which may increase stress on the pelvic floor and result in urinary incontinence, and that avoiding the supine horizontal position, especially during the second and third trimesters, can help minimize pressure from the gravid uterus on the inferior vena cava 1. However, the most recent and highest quality study on this topic is from 2020, which highlights the importance of considering the effects of increased intra-abdominal pressure on the inferior vena cava during laparoscopic procedures 1.

From the Research

Physiologic Alteration and Vena Cava Compression

• The physiologic alteration that results in compression of the vena cava during insufflation is the increase in intra-abdominal pressure 2.
• This increase in pressure can be caused by various factors, including abdominal distension or compression, which acts directly on the abdominal compartment and indirectly on the thoracic compartment, modifying circulation and ventilation 2.
• The compression of the inferior vena cava (IVC) is a result of the increased intra-abdominal pressure, which decreases venous return and increases systemic resistances as the abdominal vessels are compressed 2, 3.
• Studies have shown that the IVC collapsibility index can be used to assess the effect of intra-abdominal pressure on venous return and cardiac hemodynamics 4, 5, 3, 6.
• The relationship between intra-abdominal pressure and IVC pressure has been investigated, and it has been found that when intra-abdominal pressure is high, IVC pressure is also high, and the two pressures are highly correlated 3.

Effects of Insufflation on Vena Cava

• Insufflation with CO2 during laparoscopic surgery can cause an increase in intra-abdominal pressure, leading to compression of the IVC and decreased venous return 5.
• The effects of CO2 pneumoperitoneum on venous return and cardiac hemodynamics have been studied, and it has been found that flow through the IVC drops significantly during insufflation 5.
• However, cardiac output may rise during insufflation due to a generalized enhanced inotropic state mediated via increased sympathetic outflow 5.
• The use of IVC collapsibility index can help guide volume management and optimize cardiac output in critically ill patients requiring hemodialysis and/or ultrafiltration 6.