Is routine veno-venous bypass necessary in liver transplantation?

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.

Authors' conclusions: 

There is no evidence to support or refute the use of veno-venous bypass in liver transplantation. There is no evidence to prefer any particular technique of veno-venous bypass in liver transplantation.

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Background: 

Veno-venous bypass is used to overcome the effects of clamping of the inferior vena cava and portal vein during liver transplanation. The routine use of veno-venous bypass is, however, controversial.

Objectives: 

To compare the benefits and harms of veno-venous bypass (irrespective of open or percutaneous technique; heparin-coated or no heparin-coating) versus no veno-venous bypass during liver transplantation. To compare the benefits and harms of the different techniques of veno-venous bypass during liver transplantation.

Search strategy: 

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded until December 2010.

Selection criteria: 

We included randomised clinical trials comparing veno-venous bypass during liver transplantation (irrespective of language or publication status).

Data collection and analysis: 

Two authors independently assessed trials for inclusion and independently extracted data. We analysed the data with both the fixed-effect and the random-effects models using RevMan Analysis. For continuous outcomes, we calculated the mean difference (MD) with 95% confidence intervals (CI) based on intention-to-treat or available case analysis. For binary outcomes, we used the Fisher's exact test since none of the comparisons of binary outcomes included more than one trial.

Main results: 

We identified three trials with high risk of bias which compared veno-venous bypass (n = 65) versus no veno-venous bypass (n = 66). None of the trials reported patient or graft survival. There were no significant differences regarding renal failure or blood transfusion requirements between the two groups. None of the trials reported on the morbidity related to veno-venous bypass or the requirement of veno-venous bypass in the control group.

We identified one trial with high risk of bias which compared percutaneous (n = 20) versus open technique (n =19) of veno-venous bypass. The patient or graft survival was not reported. There was no difference in veno-venous bypass related morbidity between the two groups. The operating time was significantly shorter in the percutaneous technique group (MD -59 minutes; 95% CI -102 to -16).

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