EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Objectives: Organ donation after brain death followed by circulatory death is practiced in China. This study evaluated the application of normothermic regional perfusion to protect the liver grafts from these donors from warm ischemia in a large transplant center in China.

Materials and Methods: This prospective study involved 19 liver transplants from brain death followed by circulatory death donors that were conducted between December 2014 and June 2017. We evaluated the baseline characteristics of the donors and recipients and compared outcomes of both groups. Graft and recipient survival and postoperative complications were also analyzed.

Results: Although the normothermic regional perfusion group consisted of marginal donors with prolonged warm ischemia and recipients with higher Model for End-Stage Liver Disease scores (P < .05), postoperative tests indicated no differences in liver function recovery in both groups. Furthermore, total bilirubin decreased significantly faster in the normothermic regional perfusion group than in the control group (P < .05). Both groups showed similar 1-year recipient survival rates. No recipients in the normothermic regional perfusion group had any biliary complications, whereas 2 recipients in the control group developed ischemic cholangiopathy and received invasive treatment during follow-up.

Conclusions: In situ normothermic regional perfusion demonstrated a significant benefit in grafts from brain death followed by circulatory death donors and could potentially increase both the number and quality of donated organs.

Key words : End-stage liver disease, Ischemic cholangiopathy, Liver transplantation, Warm ischemia time

End-stage liver disease is a major cause of mortality worldwide.¹ Liver transplant has been shown to be the most effective therapy for patients with advanced liver diseases such as hepatic cirrhosis and liver cancer.² The growing demand for liver transplant in China has caused a severe shortage of donated organs. Starting in 2013, China has developed a national program for organ donation, procurement, allocation, and transplantation.³ The program adheres to the guiding principles of the World Health Organization and complies with international standards while respecting the cultural and social values of Chinese people. Unlike many countries, there is currently no legislation concerning brain death in China, and the concept of brain death has not been the norm in Chinese society. To gain widespread acceptance from the Chinese people, the Chinese classification of deceased organ donation includes a unique approach to organ donation: the China category III, which is defined as organ donation after brain death followed by circulatory death (DBCD). This practice has been promulgated throughout China and is currently the main source of organ donations in China.³

Similar to organ donation after cardiac death (DCD), liver grafts from DBCD donors are associated with increased postoperative complications, especially ischemic cholangiopathy, which is due to warm ischemia injury after circulatory cessation.^4-7 In DCD organs, normothermic regional perfusion (NRP) based on extracorporeal membrane oxygenation (ECMO) technology has been shown to effectively improve transplant outcomes.^8,9 In addition to its restoring capabilities, NRP also offers the chance to reevaluate graft status after cardiac resuscitation or hypotensive period, to better reassess uncontrolled donors.^10,11 However, because clinical experience with NRP for DBCD is so far limited, here we report a single-center experience with adult liver transplant recipients in China, in which we compare the results of the DBCD liver transplants, which often endure prolonged warm ischemia time (WIT), versus those from NRP-assisted DBCD liver donors.

Materials and Methods

Study design
This single-center prospective cohort study involved 19 liver transplant procedures from DBCDs that occurred between December 2014 and June 2017. All organs were retrieved at Zhongshan Hospital, Fudan University, with transplant procedures performed at the same institute.

Donors were selected based on the following criteria: confirmed patient identity, age < 65 years, no history of drug abuse, no active infection, and no history of malignant disease. The 19 selected donors were divided into 2 groups: the NRP group (group 1) and the control group (group 2). Donors who had one or more of the following conditions were included in group 1: (1) history of cardiac resuscitation, (2) history of hypotensive phase (systolic blood pressure < 60 mm Hg, duration time > 10 min), and (3) use of massive dose of vasoactive drugs (norepinephrine > 1.0 μg/kg/min or dopamine > 20 μg/kg/min). The remaining donors were included in group 2. Recipients were also accordingly divided into an NRP group (those in group 3 were recipients of group 1) and a control group (those in group 4 were recipients of group 2). We collected data on donors and recipients, including age, sex, biochemical data, cold ischemia time (CIT), primary disease, blood loss at surgery, Model for End-Stage Liver Disease (MELD) score, and postoperative complications.

This study was approved by the Zhongshan Hospital, Fudan University Research Ethics Committee (approval number B2015-116R). Families of donors determined the donation types, and written informed consent was obtained for each donation. The China Organ Transplant Response System conducted organ allocation equitably and transparently.

Normothermic regional perfusion management and organ procurement
The normothermic extracorporeal circuits used in this study were similar to former studies on DCD,¹¹ although a few changes were made to the protocol. The NRP circuit consisted of a pump for cardiopulmonary bypass and a membrane oxygenator. In group 1, once brain death was confirmed and the family authorized organ donation, the femoral vessels were cannulated, and a Fogarty balloon was placed in the supraceliac aorta. When maintenance treatment of donors was withdrawn, mechanical ventilation and vasopressors were stopped, and vital signs continued to be monitored. Normothermic regional perfusion was immediately started when systolic blood pressure fell below 60 mm Hg, to maintain flow of blood to liver and kidneys while awaiting cardiac arrest. Blood samples from the ECMO device were obtained just after starting NRP and at least every 30 minutes for biochemistry analyses. In group 2, withdrawal of mechanical support occurred in the operating room; before procurement, a 5-minute wait period was instituted after cardiac arrest. After confirmation of cardiac death, the DBCD organs were retrieved by a combined abdominal organ retrieval procedure.¹²

Follow-up
Levels of postoperative serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, platelet count, creatinine, and international normalized ratio (INR) were recorded and analyzed. After discharge, all transplant recipients had a minimum 12-month follow-up, with observation of complications and immunosuppression status and nutritional and social guidance every 2 months. Ischemic cholangiopathy, a major complication after liver transplant, is defined as strictures, irregularities, or dilatations of the intrahepatic or extrahepatic bile ducts. Diagnosis of ischemic cholangiopathy was based on at least one adequate imaging examination of the biliary tree, whereas concomitant hepatic artery thrombosis was excluded.

We defined WIT as time from systolic pressure below 60 mm Hg to the start of cold perfusion and CIT as time from the start of cold perfusion to organ reperfusion in the recipient.

Statistical analyses
Continuous data are presented as mean with standard deviation, and categorical data are presented as counts with percentages (%). Comparisons between group 1 and group 2 were performed using t test for continuous variables and the chi-square test for categorical variables. Covariance analysis was performed to compare trends of postoperative biochemical tests. Because of the limited number of DBCD cases and the multiple complications evaluated, associations between donor characteristics and transplant outcomes were explored descriptively. We used the Statistical Package for Social Science for Windows software for statistical analyses (version 22.0, IBM Corporation, Armonk, NY, USA). P < .05 was considered statistically significant for all analyses.

Baseline characteristics of donors and recipients
Our study included 19 DBCD liver transplant procedures, which occurred between December 2014 and June 2017. Groups 1 and 3 included 7 transplants, with the remaining transplant procedures included in groups 2 and 4. The general characteristics of the donors are listed in Table 1. We observed no significant differences in age, sex, intensive care unit (ICU) stay, and hepatic steatosis between the 2 groups (all P > .05). However, reasons for donation were slightly different. In group 1, most donors (6/7) died from a cerebrovascular accident, whereas the main cause of death in group 2 was trauma (8/12). Use of vasopressors was also significantly different between groups: all 7 donors in group 1 had received more than 1 vasopressor before organ retrieval (P < .05).

In the donor groups, WIT for group 2 was 15.7 ± 1.6 minutes (range, 14-19 min). It was not possible to record the WIT for group 1 due to the unpredictable period of the hypotensive phase. No significant differences were found in CIT between the 2 groups (4.7 ± 1.3 h for group 1 vs 4.4 ± 2.1 h for group 2; P = .751).

All donors received preoperative evaluation of the main biochemical indicators. As shown in Table 2, time 1 represents time that donors entered the ICU, and time 2 represents time before procurement. No significant differences between the 2 time segments were observed in the groups (all P > .05). However, compared with group 2, we noticed a slight trend in decreased in ALT and AST in group 1.

With regard to recipient groups, no significant differences were found in age, sex, reason for transplant, and Child-Turcotte-Pugh score in group 3 versus group 4 (P > .05; Table 3). However, the MELD score was significantly higher in group 3 than in group 4 (P = .016), and a relatively higher level of blood loss during surgery was also noted in group 3. All patients were recipients of a first transplant in this study.

Comparison of postoperative test of the recipients
All 19 recipients in this study recovered considerably well from transplant without significant early complications, such as primary graft failure, thrombosis, or graft rejection. Dynamic changes in postoperative ALT, AST, platelet count, INR, and total bilirubin levels were routinely recorded every 2 days (Figure 1). As shown in Figure 1, biochemical data results for all 19 recipients recovered to a normal level at the end of week 2 posttransplant, and no significant differences were found in trends for postoperative ALT, AST, INR, creatinine, and platelet levels between the 2 groups. However, total bilirubin decreased significantly faster in group 3 than in group 4 (P < .05). We also noticed a difference in baseline biochemical data results between the 2 groups, with initial liver function data notably higher in group 3 than in group 4, in accordance with the differences in MELD scores between the 2 groups. All liver recipients were discharged from the hospital within 30 days after transplant.

Postoperative complications
All recipients were followed for at least 12 months (range, 12-30 mo). In group 3, one patient died of severe lung infection 3 months after transplant. Other than that, no recipients in group 3 had major complications such as ischemic cholangiopathy, and liver function remained normal during the entire follow-up period. In group 4, 1 patient had an anastomotic stricture 6 months after surgery, which was alleviated with endoscopic retrograde cholangiopancreatography, and another patient had intrahepatic strictures on both sides of the hepatic ducts 8 months posttransplant, which was resolved by a Roux-en-Y conversion. The remaining recipients in group 4 showed no major complications during follow-up.

In contrast to common international practice, China has a unique category of organ donation, DBCD, which accounts for most of the donated organs in the country.³ This novel classification of donation was created based on a combination of the worldwide practice of recognizing brain death and circulatory death. Because DBCD and DCD donations are both from donors after cardiac death, WIT is the major concern affecting organ quality.^13,14 Donations after brain death followed by circulatory death that encounter cardiac resuscitation or long hypotensive phase before procurement are considered marginal donors because they are subjected to a variable and prolonged WIT, predisposing them to primary nonfunction, delayed graft function, or irreversible ischemic cholangiopathy.¹⁵ In this study, we assessed the application of NRP to include these marginal organ donations while minimizing the ischemic injury to these organs.

Normothermic regional perfusion was first applied in uncontrolled DCDs and found to be a useful approach to organ recovery.^9,16 This perfusion process has been shown to be capable of restoring organ perfusion during the hypotensive period after the withdrawal of life-sustaining therapy.^17-19 The supraceliac aorta balloon could prevent brain and/or coronary reperfusion after death declaration to avoid potential ethical controversy.²⁰ Seven marginal donors in our study group were subjected to NRP assistance before procurement. Between the NRP and control groups, most of the donors’ clinical characteristics were not significantly different, including age, sex, length of ICU stay, hepatic steatosis, and CIT. The differences in cause of death and WIT between the donor groups can be easily understood due to the recruitment criteria of our study. When we evaluated the liver/renal function of the donors at the time of entering the ICU and before procurement, no significant differences were found, indicating that all donors (especially the marginal donors) were well maintained by our medical team. However, we did note significant differences in MELD scores and blood loss (during surgery) of graft recipients. The MELD score, indicating severity of liver disease, was significant higher in the NRP group (P < .05). Although patients with more severe liver disease received marginal livers, the postoperative tests indicated that the recovery of liver function in the NRP group was not inferior to the control group. Changes in ALT, AST, platelet, and INR levels were not significantly different between the 2 groups, but the decrease of total bilirubin was much faster in the NRP group than in the control group (P < .05). This phenomenon suggests the possible protective role of NRP to prevent ischemic injury of the donor liver’s bile duct during the agonal phase.

Each recipient in this study was followed for at least 12 months. The 1-year patient survival rates of the 7 marginal DBCD donors in the NRP group were not significantly different from the control group. The only death in this study was due to an extrahepatic cause, and the patient maintained normal liver function until death. As the major complication after liver transplant, ischemic cholangiopathy is commonly recognized as a serious weakness of marginal donors, and previous researchers have observed significant increases in biliary complications with consequent decreases in graft survival in these recipients.^4,5,21 In our study, 2 of 12 recipients in the control group developed biliary complications and required surgical treatment. In contrast, no patients in the NRP group had any biliary complications during the follow-up period, suggesting that NRP could effectively prevent ischemic cholangiopathy in marginal donors.

In this study, grafts from the NRP group were all from marginal donors who had encountered prolonged WIT, and recipients in the NRP group also had higher MELD scores than the control group. Based on our results, we suggest that NRP could effectively preserve organ function and prevent postoperative complications in DBCD. Marginal donor organs that may have been discarded in the past could therefore be salvaged by this technique to the benefit of patients on wait lists.

The results of our study are encouraging, although there are several limitations. First, due to the small number of cases, the results require further verification in larger and randomized studies to confirm the real benefits of NRP and the potential to expand organ acceptance criteria. Second, the optimal parameters of abdominal NRP in DBCD need to be determined. In our study, NRP was usually maintained for 180 to 300 minutes, which is significantly longer than previous studies in DCD.^11,22 We consider that the longer duration time allows the restoration of cellular energy substrates and microvascular circulation of the biliary tree,^23,24 which eventually leads to better graft quality.

In situ NRP demonstrated a significant benefit in DBCD organ retrieval and could potentially increase both the number and quality of donated organs, especially liver donations. Further studies are needed to fully evaluate the impact on organ recovery rates and further determine the detailed parameters of this technique.

Volume: 18 Issue: 1 February 2020

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