Factors during donor care that may affect liver transplantation outcome

Progress in Transplantation, Sep 2004 by Powner, David J

Publications are reviewed that identify factors during donor care and characteristics of the donor liver that may be associated with outcome following liver transplantation. The procurement coordinator has the opportunity to influence cold ischemia time, blood pressure, the serum sodium concentration and, perhaps, liver glycogen reserves. These variables may significantly affect postimplantation graft performance and graft or recipient survival. Summaries of those publications comprising this database are presented, and several limitations in their interpretation are discussed. (Progress in Transplantation. 2004; 14:241-249)

Notice to CE enrouées:

A closed-book, multiple-choice examination following this article tests your ability to accomplish the following objectives:

1. Identify factors of a liver donor not amenable to change

2. Explore factors amenable to change and how they can optimally affect liver transplant outcome

3. Understand limitations of the database presented

Many studies and expert reviews1-5 explore a possible association between characteristics of a donor liver and its successful or unsuccessful function in a recipient. Publications from the PubMed database (1974-2004), the author's files, and other citations from those sources addressed factors (Table 1) that may adversely affect liver function after transplantation. Table 2 provides more detailed information about those publications.

Many properties of the donor liver and aspects of donor care are important to the receiving surgeon as he or she considers a liver. Some characteristics such as the donor's age, sex, blood type, and cause of death influence allocation decisions but cannot be altered during donor care. The procurement coordinator must be aware of those factors during the allocation process, but should also be focused on variables that, if modified, might maximize later graft performance. This discussion will emphasize those variables.

Limitations of the Database

It is important to acknowledge several limitations in this analysis. Not only do these limits apply to this discussion, but they should also be considered by organ procurement coordinators when reading similar articles.

Most articles cited here used a similar study design. A group of donors were identified, characteristics selected, and some measure of outcome evaluated after transplantation. Data were usually collected retrospectively, and several statistical tests were used to measure if the relationship between donor and outcome variable(s) reached statistical significance.

Only studies of human donors have been reviewed because animal experiments cannot be directly applied to the care of human donors. Including only human data, however, usually restricts available information to noninterventional observations. Ethical considerations in human experimentation often limit studies that compare a "control" group and a second "experimental" donor group. Few of these studies grouped donors so that factors other than those to be examined were similar. Using such a research technique might allow some "control" or balance of other variables that could influence outcome measures and thus improve the ability to detect an effect from the factor of interest.

Most articles reported retrospective rather than prospective data acquisition. In this type of study design, many physiological or treatment variables throughout donor care were not known and/or not presented. These "uncontrolled" factors and nonstandardized care practices may have had some unknown effect on the donor liver.

Of great concern when attempting to interpret uncontrolled data is that a cause-and-effect relationship is implied between the variable selected and the outcome found. This assumption of causality can be especially inappropriate when analyzing a process as physiologically complex as donor care. Many unacknowledged or unknown factors could have affected the outcome measure slightly, as much as, or more than the variable chosen for evaluation. Readers must, therefore, be reluctant to assume that a statistical "association" found between a factor and an outcome proves that the factor alone caused the change.

The characteristics of the donor liver and the care provided to it before removal are important. However, the liver is further subjected to explantation cold ischemia, implantation warm ischemia, alternative perfusion solutions, possible injury during surgery and reperfusion, and the physiological environment and initial treatment of the recipient before many measures of outcome are known. Perioperative or intraoperative factors are likewise nonstandardized and may be unreported, but they could affect outcomes in unknown ways.

The effects of several potentially adverse factors in the same donor (eg, older age, prolonged hypotension) may be additive. The importance of each factor and how combinations of factors may harm the liver have been explored,8,12,17,20 but no precise method has been developed to weigh or predict the individual or combined effects of the various factors.1,12 The possibility of considering combinations of donor and recipient risk factors so as to match high-risk donors with lower risk recipients or vice versa has also been suggested, but the benefit of doing so is unproven.1