Use of Older Donor Livers Is Associated With More Extensive Ischemic Damage on Intraoperative Biopsies During Liver Transplantation

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1 Use of Older Donor Livers Is Associated With More Extensive Ischemic Damage on Intraoperative Biopsies During Liver Transplantation Marc Deschênes,* Clark Forbes, Jean Tchervenkov, Jeffrey Barkun, Peter Metrakos, Joe Tector, and Elliott Alpert* SEE EDITORIAL ON PAGE 458 Initial poor graft function is associated with increased morbidity and graft loss after liver transplantation. Donor age is a risk factor for the development of initial poor function. The severity of ischemic damage on intraoperative postreperfusion (0Post) allograft biopsy specimens is predictive of subsequent initial poor function. This study was performed to assess whether donor age is a risk factor for the development of ischemic damage on 0Post biopsy specimens. The records of 94 liver transplantations were reviewed. 0Post biopsy specimens were obtained after complete allograft revascularization. The severity of ischemic damage was graded as follows: 0, none; 1, minimal; 2, mild; 3, moderate; and 4, severe. Grafts were defined as older when donor age was 50 years or older. Other independent variables examined included donor cause of death, length of hospital stay, acidosis, serum alanine aminotransferase level, graft cold ischemia time, and degree of steatosis. Older grafts were associated with higher grades of ischemic damage than younger grafts ( v ; P.003). Univariate and multivariate analysis identified donor age of 50 years or older as the only significant predictive variable of the severity of ischemic damage. In 16 transplantations involving older grafts, there was no statistically significant association between the severity of ischemic damage and incidence of initial poor function and graft loss. The use of older liver grafts is associated with more extensive ischemic damage immediately after graft reperfusion. Whether this early lesion identifies among older graft recipients those at risk for a worst outcome remains to be determined. Copyright 1999 by the American Association for the Study of Liver Diseases T he success of liver transplantation 1 has led to an increasing number of patients being enrolled on the waiting list, with a concomitant shortage in donor organs. 2 One solution has been to liberalize selection criteria; in particular, to use organs from older donors. However, donor age of 50 years or older is a risk factor for the development of initial poor graft function after liver transplantation. 3-5 Initial poor graft function is associated with increased recipient morbidity, resource utilization, and graft loss after liver transplantation. 5,6-9 The severity of ischemic damage on intraoperative allograft biopsy specimens taken after reperfusion is predictive of postoperative histological preservation injury and initial poor graft function defined on the basis of elevated aminotransferase levels. 10,11 This study was performed to assess whether donor age is a risk factor for the development of this early histological ischemic lesion on intraoperative postreperfusion (0Post) allograft biopsy specimens and whether it identifies among older grafts those at greater risk for initial poor function and graft loss after liver transplantation. Materials and Methods We reviewed the records of the 122 consecutive adult liver transplantations performed in 99 recipients at our institution between January 1991 and July The 94 liver transplantations with complete data sets that included a 0Post liver allograft biopsy during transplantation constituted our study population. All allografts were preserved in University of Wisconsin solution by established methods. The selection of donors as good candidates was based on clinical, biochemical, surgical, and From the Departments of *Medicine, Pathology, and Surgery, Liver Transplant Program, Royal Victoria Hospital, McGill University Health Center, Montréal, Québec, Canada. Address reprint request to Marc Deschênes, MD, Royal Victoria Hospital, R2.28, 687 Pine Ave West, Montréal, Québec, Canada H3A 1A1. Copyright 1999 by the American Association for the Study of Liver Diseases /99/ $3.00/0 Liver Transplantation and Surgery, Vol 5, No 5 (September), 1999: pp

2 358 Deschênes et al histological findings. Reduced-size grafts were not used, and all patients received a blood-group compatible allograft. Warm ischemia time, defined as the time between implantation in the recipient and reestablishment of blood flow, was 60 minutes or less for all transplants. Venovenous bypass was not used in any transplantations. Arterialization of the graft was performed after caval and portal flow were reestablished. 0Post hepatic allograft biopsy specimens were obtained after reperfusion and complete revascularization of the allograft in all patients. All biopsy specimens were fixed in 10% buffered formalin, processed, embedded in paraffin, and stained with hematoxylin and eosin before evaluation. All 0Post wedge biopsy specimens were assessed histologically by one pathologist for the severity of ischemic damage and extent of donor steatosis. The severity of ischemic damage in 0Post biopsy specimens was graded prospectively using a semiquantitative numerical scoring system based on previously published observations by Kakizoe et al. 10 The specific histological changes assessed were (1) graft infiltration by acute inflammatory cells and (2) the presence of hepatocellular damage defined by the presence of coagulative necrosis, ballooning degeneration, or cytoaggregation of hepatocytes. The severity of ischemic damage was scored as follows: 0, 0 to 1 sinusoidal neutrophils per high-power field (hpf) with no hepatocellular damage; 1, 2 to 5 lobular neutrophils/hpf and/or less than 10% hepatocellular damage; 2, 6 to 10 lobular neutrophils/hpf and/or 10% to 40% hepatocellular damage; 3, 11 to 20 lobular neutrophils/hpf and/or 40% to 70% hepatocellular damage; and 4, greater than 20 lobular neutrophils/hpf and/or greater than 70% hepatocellular damage. The grading of the severity of ischemic damage was based on the evaluation of the most severely affected areas of the 0Post biopsy specimens. The severity of neutrophil sequestration and extent of hepatocellular damage showed a close relationship. The degree of macrovesicular steatosis was assessed separately on a scale of 0 to 3, in which 0 represented absent; 1, fat present in less than 33% of hepatocytes; 2, fat present in greater than 33% but less than 66% of hepatocytes; and 3, fat present in greater than 66% of hepatocytes. Liver grafts were defined as older for donor age of 50 years or older. Other donor-related variables examined included sex, cause of death, length of hospital stay, preprocurement acidosis (ph 7.30), and serum alanine aminotransferase level. Graft cold ischemia time was also recorded. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Liver Transplantation Database definition of early allograft dysfunction (EAD) was used to assess the incidence of initial poor graft function after liver transplantation. 5 EAD was defined as the presence of at least one of the following factors between days 2 and 7 after liver transplantation: (1) serum total bilirubin level greater than 10 mg/ml; (2) prothrombin time, 17 seconds or greater; or (3) hepatic encephalopathy. Graft survival at 6 months and 1 year was also recorded. Potential risk factors were analyzed for their effect on the grade of severity of ischemic damage on 0Post biopsy specimens using Sigma Stat 1.0 (Jandel Scientific Software, San Rafael, CA). Continuous variables were compared using Student s t-test and one-way ANOVA, and categorical variables were compared using Chi-squared analysis or Fisher s exact test when appropriate. Correlations were studied using Pearson s product moment. Unless specified otherwise, results are expressed as mean 1 SD. A difference was considered statistically significant for P less than.05. Multivariate analysis was performed using an F-to-remove strategy 12 with a significance level of P equal.05 in deciding which variable(s) should be retained or removed from the regression model. Results Of the grafts studied, 83 (88%) were used for a first transplantation and 11 (12%) for a retransplantation. Mean donor age was years. Sixteen grafts (17%) originated from older donors. Fortyeight grafts (51%) were from female donors. The grade of ischemic damage observed on 0Post biopsy specimens was 0 in 26%, 1 in 21%, 2 in 37%, 3 in 12%, and 4 in 4%. Table 1 shows the grade of ischemic damage for the various donor age groups. The grade of ischemic damage in older grafts was compared with in younger grafts (P.003). Older grafts also showed higher grades of steatosis than younger grafts ( v ; P.03). There was no difference in the grade of steatosis of grafts from female ( ) and male donors ( ; P.9). The cause of Table 1. Grade of Ischemic Damage on 0Post Allograft Biopsy Specimens Based on Donor Age Group Donor Age (y) No. of Specimens Grade of Ischemic Damage (%)

3 Ischemic Damage During Liver Transplantation 359 death of older donors differed from that of younger donors: cerebrovascular accident, 73% versus 35%; trauma, 20% versus 47%; and other causes, 13% versus 18%, respectively (P.04). The effects of the examined variables on severity of ischemic damage observed on 0Post biopsy specimens are shown in Table 2. Both univariate (Table 2) and multivariate analyses identified donor age of 50 years or older as the only significant predictive variable of the severity of ischemic damage on 0Post allograft biopsy specimens (r 0.31; P.02). The grade of ischemic damage seen on 0Post biopsy specimens in 16 liver transplants when older grafts were used was as follows: 0, n 0 (0%); 1, n 4 (25%); 2, n 6 (38%); 3, n 4 (25%); and 4, n 2 (12%). The rate of EAD after liver transplantation was 38% for older grafts compared with 27% for younger grafts (P.56). For each grade of ischemic damage seen on 0Post biopsy specimens, the incidence rate of EAD after liver transplantation using these older organs was as follows: grade 1, 50%; grade 2, 33%; grade 3, 0%; and grade 4, 100% (P.11). The 6-month graft survival rate when using older grafts was 75% versus 86% for younger grafts (P.47); 1-year graft survival rate was 69% for older grafts versus 83% for younger grafts (P.35). The grade of ischemic damage seen on 0Post biopsy specimens in four older grafts lost within 6 months of transplantation was compared with in 12 grafts that survived 6 months (P.26). Discussion Our results show that the use of older liver organs is associated with more extensive ischemic damage of the graft seen on 0Post liver biopsy specimens during transplantation. However, the presence of this early lesion did not translate into worst clinical outcomes as reflected by the incidence of EAD and graft loss when older grafts were used. Because of the shortage of donor organs and the increasing waiting times for liver transplantation, we have been forced to use livers from older donors. They constitute approximately one fifth of the organs that we used for liver transplantation. Aging of the normal liver is associated with a few alterations, such as a decrease in the overall weight of the organ and, morphologically, larger and fewer hepatocytes and an increase in the pigment and protein content of the cells. 13 Recently, mitochon- Table 2. Effect of Donor and Graft Variables on the Severity of Ischemic Damage on 0Post Allograft Biopsy Specimens Variables 0 (n 24) 1 (n 20) Grade of Ischemic Damage 2 (n 35) 3 (n 11) 4 (n 4) Donor Age 50 years* Cause of death*.26 Cerebrovascular accident Trauma Other Length of hospital stay Pre-procurement acidosis* ALT (U/L) Graft Cold ischemia time (h, min) 10, 45 4, 39 10, 20 5, 11 9, 26 4, 11 13, 00 4, 41 8, 06 2, Steatosis* *Percentage of total number of patients with given ischemic grade. Median. P

4 360 Deschênes et al drial defects of the respiratory chain that affect normal aging livers have been described. 14 These may decrease the adaptive capacity of such organs when they undergo the stress of preservation and reperfusion. Several studies now indicate that donor age is a relative risk factor for the development of initial poor graft function after liver transplantation. 3,5,7,15-17 The presence of sinusoidal neutrophilia and hepatocellular necrosis in 0Post biopsy specimens is clinically relevant because these findings correlate with both the histological lesion of preservation injury and poor initial graft function after liver transplantation. 10,11,18 Also, initial poor function of the newly implanted graft is associated with increased recipient morbidity and mortality after liver transplantation. 5-7 We found that older liver grafts developed more extensive ischemic injury early after graft reperfusion. Older grafts were also more steatotic. However, when the donor age variable was examined along with other known possible donor and graft relative risk factors for initial poor graft function, 3,5 it was identified as an independent predictor of this early ischemic lesion on 0Post biopsy specimens. We used the incidence rate of EAD after liver transplantation to assess whether the severity of ischemic damage seen on 0Post biopsy specimens from older grafts was predictive of initial poor graft function. EAD is a definition of initial poor graft function based on readily available indices of liver function. 5 It was developed from the NIDDK Liver Transplantation Database and has been tested on another patient sample. 19 The presence of EAD is associated with greater recipient morbidity and graft loss after liver transplantation. 5,19 However, we did not observe that older-graft recipients with ischemic damage on 0Post biopsy specimens had a greater incidence of EAD and graft loss after liver transplantation. Although intuitively it would make sense that such is the case, this still remains to be determined. To comprehensively address this issue, a much larger sample of older-graft recipients will be required than that of the present study, and pre liver transplant recipient risk factors for initial poor graft function will also need to be examined. Although this early histological lesion was of limited value in predicting initial poor graft function in our study and, as a postoperative finding, is of course not helpful in donor selection, it represents an additional outcome variable that can be examined in the study of preservation/reperfusion injury. This additional intermediate end point may be useful given the absence of an accepted nomenclature in defining initial poor graft function. At any rate, we can ill afford in this current era of organ shortage not to make use of these older donors. We need to address the risk factors for this early ischemic lesion in this particular subgroup of grafts that now constitutes an important contribution to our donor pool. Known relative risk factors for initial poor graft function, such as depletion of hepatic adenosine triphosphate stores, 20,21 increased glycogen breakdown, 22 reduction in hepatic mitochondrial redox potential, 23 and nutritional status of the donor, as well as other variables yet to be identified, need to be reexamined in light of our present and future understanding of the normal physiological changes associated with aging of the liver. Possible changes to the organ allocation scheme to diminish the combination of various risk factors for initial poor graft function for a given transplant should also be studied. 5 In summary, the current study indicates that the use of older donor livers is associated with more extensive ischemic damage on 0Post allograft biopsy specimens. Our sample size was too small to show that these histological changes are associated with a greater incidence of initial poor graft function and graft loss with this particular subgroup of organs. However, this lesion has previously been associated with a worst clinical outcome after liver transplantation. Future studies need to better define the relevant preoperative risk factors involved, as well as their pathophysiological impact, so we can design strategies to minimize the incidence of initial poor graft function after liver transplantation. The histological findings of 0Post graft biopsy specimens may be a useful additional intermediate end point to examine in such studies. Acknowledgment The authors thank Myriam Fernandez for her technical assistance with the computerized Royal Victoria Hospital Liver Transplantation Database. References 1. Starzl TE, Demetris AJ, Van Thiel D. Liver transplantation. N Engl J Med 1989;321: , Guo TJ, Daily OP, Davies DB. The UNOS OPTN waiting list: 1988 to United Network for Organ Sharing. Organ Procurement and Transplantation Network. Clinical Transpl 1994:69-86.

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