Techniques of reperfusion for liver transplantation

The liver is the powerhouse of the body and is nourished by two sources of blood supply, oxygenated blood (via the hepatic artery) and partly oxygenated blood that transports the digested carbohydrates and proteins directly from the intestines to the liver). In a healthy individual, the portal vein contributes to more than three-quarters of the blood supply to the liver (via the portal vein). The de-oxygenated blood from the liver is then drained by a large vein, called the inferior vena cava, into the heart. When the donor liver is removed, its blood vessels are flushed with storage solution in order to prevent thrombosis of the vessels and to preserve the liver. During removal of the liver from the cadaveric donor, the liver is removed with an adequate length of blood vessels. These blood vessels are then connected to the blood vessels in the recipient to restore the blood flow. The inferior vena cava and portal veins are connected before connecting the hepatic artery. The blood flow is then generally restored via the portal vein and the arterial anastomosis is performed after restoring the circulation to the liver via the portal vein. This restoration of circulation to the liver is called reperfusion. Before the blood flow is restored, the storage solution within the donor liver is flushed out so that large amounts of used storage fluid does not enter the recipient blood circulation, which can cause problems with the functioning of the heart. This is usually performed using a second solution, such as a protein solution, via the portal vein. Some transplantation surgeons have suggested that flushing the storage solution through the hepatic artery or letting out blood (in addition to the storage fluid) may improve the outcomes after transplantation. Others have suggested that restoring the circulation through the hepatic artery either initially or simultaneously with portal vein reperfusion may improve the outcomes. Yet others have suggested that restoring the circulation by reverse flow (retrograde reperfusion) through the inferior vena cava may improve the outcomes. The optimal technique of flushing and reperfusion is not known. We performed a detailed review of the medical literature (until March 2011) to determine the benefits and harms of different techniques of flushing and reperfusion in patients undergoing liver transplantation. We sought evidence from randomised clinical trials only. When conducted properly, such trials provide the best evidence. Two authors independently identified the trials and obtained the information from the trials.

We included six trials involving 418 patients for this review. The number of patients included in the trials varied from 30 to 131. Most of the trials were at high risk of systematic errors (ie, there was a potential to arrive at wrong conclusions because of the way the trial was conducted) and random errors (there was a potential to arrive at the wrong conclusions because of the play of chance). The comparisons performed included initial hepatic artery flush versus initial portal vein flush; blood venting via the inferior vena cava in addition to venting of storage fluid versus no blood venting; initial hepatic artery reperfusion versus initial portal vein reperfusion; simultaneous hepatic artery and portal vein reperfusion versus initial portal vein reperfusion; and retrograde inferior vena cava reperfusion versus simultaneous hepatic artery and portal vein reperfusion. There were no significant differences in the risk of death or graft loss, or in the major complication rates, between the compared groups in any of the comparisons. Quality of life was not reported in any of the trials. There were no significant differences in the transfusion requirements, intensive therapy unit stay, or hospital stay between the compared groups in any of the comparisons. We are unable to advocate or refute any technique of flushing and reperfusion in patients undergoing liver transplantation. Further well designed trials with low risk of systematic error and low risk of random errors are necessary.

Authors' conclusions: 

There is currently no evidence to support or refute the use of any specific technique of flushing or reperfusion during liver transplantation. Due to the paucity of data, absence of evidence should not be confused with evidence of absence of any differences. Further well designed trials with low risk of systematic error and low risk of random errors are necessary.

Read the full abstract...
Background: 

Various techniques of flushing and reperfusion have been advocated to improve outcomes after liver transplantation. There is considerable uncertainty as to which method is superior.

Objectives: 

To compare the benefits and harms of different methods of flushing and reperfusion during liver implantation in the transplant recipients.

Search strategy: 

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded until March 2011.

Selection criteria: 

We included all randomised clinical trials that were performed to compare different techniques of flushing and reperfusion during liver transplantation.

Data collection and analysis: 

Two authors independently identified the trials and extracted the data. We analysed the data with both the fixed-effect model and the random-effects model using RevMan analysis. For each outcome we calculated the hazard ratio (HR), risk ratio (RR), rate ratio, mean difference (MD), or standardised mean difference (SMD) with 95% confidence intervals (CI) based on available case analysis.

Main results: 

We included six trials involving 418 patients for this review. The sample size in the trials varied from 30 to 131 patients. Only one trial involving 131 patients was of low risk of bias for mortality. This trial was at high risk of bias for other outcomes. Four trials excluded patients who underwent liver transplantation for acute liver failure. All the trials included livers obtained from cadaveric donors. The remaining five trials were of high risk of bias for all outcomes. Liver transplantation was performed by the conventional method (caval replacement) in two trials and piggy-back method (caval preservation) in one trial. The method of liver transplantation was not available in the remaining three trials. The comparisons performed included an initial hepatic artery flush versus initial portal vein flush; blood venting via inferior vena cava in addition to venting of storage fluid versus no blood venting; initial hepatic artery reperfusion versus initial portal vein reperfusion; simultaneous hepatic artery and portal vein reperfusion versus initial portal vein reperfusion; and retrograde inferior vena cava reperfusion versus simultaneous hepatic artery and portal vein reperfusion. Only one or two trials could be included under each comparison. There was no significant difference in mortality, graft survival, or severe morbidity rates in any of the comparisons. Quality of life was not reported in any of the trials.

Share/Save