A comparison of passive and active shunting for bypass of the retrohepatic IVC

In order to provide improved shunting of caval blood around the liver for major juxtahepatic venous injuries, a modification of the venovenous bypass (active shunt) used in liver transplantation was developed. Using a porcine model, hemodynamic comparisons of active shunting with an interposed Bio-Medicus pump (group I: n = 6) and passive shunting (group II: n = 4) around the liver for 60 minutes were made. One end of the shunt was placed in the infrahepatic cava and the other end was inserted into the right atrium. Systolic blood pressure (sBP) and cardiac output (CO) were well maintained in group I. However, with passive shunting (group II), sBP fell from 134 +/- 28 to 83 +/- 28 mm Hg (p less than 0.05) and CO fell from 4.1 +/- 0.07 to 1.3 +/- 0.5 L/min (p less than 0.001) after 1 hour. The well-maintained sBP and CO in group I were associated with much better shunt flow rates than in group II (31 +/- 7 vs. 11 +/- 3 mL/kg/min) (p less than 0.001). The cause of the fall in sBP and CO with the passive shunt (group II) in spite of a well-maintained PAWP is unclear at this time. Thus, it appears that active shunting of blood around the liver using a venovenous bypass with a pump is much superior hemodynamically to passive shunting, which relies only on hydrostatic pressure.