During liver transplantation major veins are clamped (blocked using clamps) by the surgeon in order to complete the operation. This can decrease the blood returning to the heart which has the potential to decrease the blood pressure and the blood flow to the vital organs. To avoid this, diverting the blood flow through an external circuit bypassing the clamps and returning this blood to the heart (veno-venous bypass) has been advocated by some. However, the use of veno-venous bypass is associated with a risk of major life threatening complications and also minor complications. Thus, the use of veno-venous bypass is controversial.
We systematically searched various medical databases to determine whether veno-venous bypass is required routinely during liver transplantation. We identified a total of three randomised clinical trials with high risk of systematic error and high risk of random errors which compared veno-venous bypass (n = 65) with no veno-venous bypass (n = 66). None of the trials reported patient or graft survival. There were no differences regarding kidney failure or blood transfusion requirements between the two groups. None of the trials reported on the complications related to veno-venous bypass or the requirement of veno-venous bypass in the control group. We also identified one trial with high risk of systematic error and high risk of random errors which compared needle technique (percutaneous approach) (n = 20) with open technique (n =19) of veno-venous bypass. The patient or graft survival was not reported in this trial. There was no difference in veno-venous bypass related complications between the two groups. The operating time was shorter in the percutaneous technique group. There is currently no evidence to support the routine use of veno-venous bypass in liver transplantation.