Intraperitoneal and retroperitoneal carbon dioxide insufflation evoke different effects on caval vein pressure gradients in humans - Evidence for theStarling resistor concept abdominal venous return

Background: The authors hypothesized that intraperitoneal and retroperitone al carbon dioxide insufflation during surgical procedures evoke markedly di fferent effects on the venous low-pressure system, induce different inferio r caval vein pressure gradients at similar insufflation pressures, and may provide evidence for the Starling resistor concept of abdominal venous retu rn. Methods: Intra- and extrathoracic caval vein pressures were measured using micromanometers during carbon dioxide insufflation at six cavity pressures (baseline and 10, 15, 20, and 24 mmHg and desufflation) in 20 anesthetized patients undergoing laparoscopic (supine, n = 8) or left (n = 6) or right ( n = 6) retroperitoneoscopic (prone position) surgery. Intracavital, esophag eal, and gastric pressures also were assessed. Data were analyzed for insuf flation pressure-dependent and group effects by one-way and two-way analysi s of variance for repeated measurements, respectively, followed by the Newm an-Keuls post hoc test (P < 0.05). Results: Intraperitoneal, unlike retroperitoneal, insufflation markedly inc reased, in an insufflation pressure-dependent fashion, the inferior-to-supe rior caval vein pressure gradient (P < 0.00001) at the level of the diaphra gm. In contrast to what was observed with retroperitoneal insufflation, tra nsmural intrathoracic caval vein pressure increased at 10 mmHg insufflation pressure, but the increase flattened with an insufflation pressure of more than 10 mmHg, and pressure decreased with an inflation pressure of 20 mmHg (P = 0.0397). These data are consistent with a zone 2 or 3 abdominal vascu lar condition during intraperitoneal and a zone 3 abdominal vascular condit ion during retroperitoneal insufflation. Conclusions: Intraperitoneal but not retroperitoneal carbon dioxide insuffl ation evokes a transition of the abdominal venous compartment from a zone 3 to a zone 2 condition, presumably impairing venous return, supporting the Starling resistor concept of abdominal venous return in humans.