Outcomes for primary kidney transplantation from donation after Citizens’ death in China: a single center experience of 367 cases

Background The cases of donation after brain death followed by circulatory death (DBCD) and donation after cardiac death (DCD) have been increased year by year in China. Further research is needed to understand in the outcomes and risk factors of delayed graft function (DGF) in order to minimize the risk of DGF and ameliorate its potential impact on long-term outcomes. This study was to explore the differences in outcomes between DBCD and DCD transplant and the main risk factors for DGF in DBCD. Methods Retrospective analysis of the clinical data of 367donations after citizens’ death kidney transplant procedures (donors and recipients) between July 2012 and August 2015 at our center. Results During the study period, the donation success rate was 25.3%. 164 cases of DBCD and 35 cases of DCD had been implemented and 367 kidneys were transplanted. The incidence of DGF in DBCD group were significantly lower than that of DCD group (12.0% vs. 27.0%, p = 0.002). The 1-year percent freedom from acute rejection (AR) was significantly higher in DBCD group compared with it of DCD group (94% vs. 82%, p = 0.036). Multivariate logistic regression analysis of the kidney transplants revealed that the high risk factors for DGF after renal transplantation in DBCD were history of hypertension (Odds Ratio [OR] = 5.88, 95% CI: 1.90 to 18.2, p = 0.002), low blood pressure (BP < 80 mmHg) (OR = 4.86, 95% CI: 1.58 to 14.9, p = 0.006) and serum creatinine of donor (OR = 1.09, 95% CI: 1.03 to 1.16, p = 0.003) before donation. Conclusions The outcomes of DBCD could be better than DCD in DGF and AR. The main risk factors for DGF in DBCD kidney transplants are donors with a history of hypertension, low blood pressure, and serum creatinine of donor before donation.


Background
Donation after cardiac death (DCD) and donation after brain death (DBD) are two processes for organ donation. Transplant technology and experiences with DCD and DBD resources are now highly advanced, and the transplantation outcomes of both organ resources processes are well explored [1]. Although DBD has been accepted in Western nations for a long time, a vast majority of people in the Chinese society have not fully accepted the Harvard brain death criteria [2], besides, the relevant laws on brain death have not yet to be approved in China [3]; thus, potential donors who meet the brain death criteria still have to wait for cardiac arrest before donation, which donation was named controlled DCD after brain death or donation after brain death followed by circulatory death (DBCD).
In 2012, Dr. Qiu and his colleagues summarized the introduction of DBCD in China as a new protocol for deceased donations, which responded to brain death not being legally recognized in China [4]. Additional recent studies of clinical outcomes have shown that pediatric DBCD kidney donation for transplant is also feasible [5]. Furthermore, the DBCD program adheres to the guiding principles of the World Health Organization, and is compliant with the Declaration of Istanbul. In 2012 and 2014, Professors Huang and Sun published China DBCD-related policies regarding the implementation of standards and specifications in The Lancet [3,6].
Delayed graft function (DGF) is an early complication after deceased donor kidney transplantation with significant adverse effects on graft outcomes. One of the major concerns of kidneys from DCD donors is the high incidence of DGF observed after transplantation. The harmful impact of DGF on graft outcomes in DBD transplant is well documented [2,[7][8][9]. However, there was no related report on clinical outcomes of kidneys from DBCD donors.
In China, the cases of DBCD and DCD have been increased year by year. Further research is needed to understand in the outcomes and risk factors of DGF in the DBCD transplants, so that to minimize the risk of DGF and ameliorate its potential impact on long-term outcomes. The aim of this study was to compare the outcomes of DBCD transplants with those of DCD transplants, and explore the risk factors of DGF among patients with DBCD kidney transplantation.

Design
This was a single-center, retrospective cohort study conducted at the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China. Data were obtained from the registry system of organ donation database, which collects all data prospectively. All patients who received a deceased-donor kidney-only transplant from July 2012 to August 2015 were included in this study. Recipients were regularly followed up post transplant. The follow up time points were the first month, the second months, the third month, the sixth month, 1 year after kidney transplantation, then once a year. The median follow up time was 317 days, range from 1 day to 700 days. Recipients were divided into two groups based on the type of donor DBCD and DBD. End points studied were patient survival and uncensored graft survival. Other end points included DGF, AR, and infection in the first year.

Donors and recipients information
A Donation after Citizens' Death flow chart for donors in China is briefly shown in our previous study [10]. Acceptable criteria for donors include: donor is identified; no history of kidney disease, drug abuse, uncontrolled hypertension, diabetes mellitus with complications, malignancy and systemic sepsis; no active HIV infection; donor age ≤ 65 years old; warm ischemia time ≤ 60 min (life-support withdrawal to aortic in situ cold perfusion). Kidneys of donation after citizens' death were regionally distributed within the organ sharing network system of China, which is similar to the United Network for Organ Sharing.
Three hundred sixty seven kidney transplant cases derived from 199 donors were completed in our center, in accordance with the donation after citizens' death standard implementation at our local organ procurement organization (OPO). The family members (parents, spouses, and adult children) of the donors agreed to the organ donation after cardiac death, and signed a voluntary organ donation form and other related documents. Organs were recovered after removal of the donor from mechanical ventilation and 2~5 min after confirmation of cardiac death. All kidneys were preserved by hypothermic machine perfusion (Life Port Kidney Transporter, Shanghai Genext Medical Technology Co., Ltd.). A kidney transplantation would not be performed if machine perfusion parameters showed that a flow rate < 80 mL/ min and/or resistant index >0.4. The characteristics of the donors and recipients were reported in Tables 1 and 2.

HLA typing and epitope mismatch identification
High-resolution HLA typing (HLA-A, −B,-C, −DR, and -DQ) was performed using sequence-specific oligo nucleotide probes (LAB Type_HD SSO, One Lambda, Canoga Park, CA, USA). HLA types A, B, and DR (three pairs and six antigens) are used for matching before kidney transplantation. All of the recipients were complementdependent-cytotoxicity-crossmatch negative and therefore considered to be at low risk of early AR.
Anti-infective prophylaxis included oral intake of sulfamethoxazole/trimethoprim for 6 months and intravenous administration of valganciclovir for 2 weeks, which was initiated immediately and after 2 months post-transplantation, respectively. This was followed by maintenance therapy with oral ganciclovir for at least 3 months, depending on donor and recipient cytomegalovirus (CMV) serological status.

Definitions
DGF was defined as a serum creatinine concentration at postoperative day 7 of >2.5 mg/dL or the need for dialysis during the first week after transplantation.
AR was identified on biopsy and classified according to the Banff'07 classification and its subsequent updates [11]. AR was suggested clinically by an unexplained rise in serum creatinine concentration of >0.3 mg/dL or a 25% increase from baseline, and was confirmed by ultrasound-guided percutaneous biopsy. The incidence, time, and therapy for AR were noted within 12 months after transplantation.
The infections within the first year of kidney transplantation were also explored in this study, including pulmonary infection, urinary tract infection, and incision infection.

Post-transplantation monitoring
Serum concentrations of total bilirubin, alanine aminotransferase, albumin, blood urea nitrogen, and serum creatinine were measured using an automatic biochemistry analyzer (7170, Hitachi, Tokyo, Japan). The blood trough concentrations of CsA, TAC and Mycophenolic acid (MPA) were measured regularly using an enzyme multiplied immunoassay (Siemens Healthcare Diagnostic, Camberley, UK). The PRA and donor-specific antibody (DSA) were screened using the Luminex 200 system (Luminex, Austin, TX, USA).

Statistical analysis
Data were analyzed by SPSS® version 17.0. Categorical data were compared using the Chi-square tests or Fisher's exact tests, while continuous data were analyzed using Mann-Whitney U test or Student's t test, as appropriate. Kaplan-Meier non-parametric methods were

Characteristics of donors and recipients
Among the 786 families in our study, 587 families did not give consent to donate organs of potential donors, while the remaining 199 families provided consent.

Outcome of transplantation
As described in Table 3, the incidence of DGF in DBCD group were significantly lower than that of DCD group (12.0% vs. 27.0%, p = 0.002), and one-year percent freedom from AR was higher in DBCD group compared with it of DCD group (94% vs. 82%, p = 0.036), respectively (Fig. 1). Those differences stayed significant after the death cause of donor and BMI of recipient were adjusted. The 1-year patients survival rate of DBCD and DCD group was 97% and 94% (p = 0.768) (Fig. 2). No different between the two groups were found on graft excision rates (DBCD 3.3% vs. DCD4.7%, p = 0.707), and one-year percent freedom from infection (DBCD 85% vs. DCD 88%, p = 0.431) (Fig. 3).

Risk factors of DGF occurrence within DBCD
Results of univariate analyses for the risk factors of DGF were reported in Table 4 (Table 5). Vasopressor agents (OR = 0.27, 95% CI: 0.11 to 0.71, p = 0.008) was benefits factor for DGF in our study.

Discussion
The DBCD donation cases in our study are cases of waiting cardiac or circulatory death includes patients for whom circulatory death occurs after a planned withdrawal of life-sustaining therapies. The DCD donation cases of ours include sudden unexpected circulatory arrest without any attempt of resuscitation, sudden unexpected irreversible circulatory arrest with unsuccessful resuscitation, and sudden circulatory arrest after brain death diagnosis. Actually, the definition of Chinese term "DBCD" and DCD are identical with some contents of "Controlled DCD" and "Uncontrolled DCD" as described by Marie Thuong, et al. in 2016 [12, 13]. In Table 6, Organ donation in China was classified into the Maastricht Classification of DCD according to the modified Maastricht Classification of DCD [12]. The research data of DCD renal transplantations carried out in Europe and reported by Moers, Kokkinos, and Jochmans show that the rate of DGF in DBD and DCD transplants were 13-35 and 28-88% respectively [14][15][16]. In 2011, the data from Wake Forest University revealed that the incidence of AR after kidney transplantation was 28.6% for DCD kidneys and 16.1% for DBD kidneys. The incidence rates of infection after renal transplantation for DCD and DBD were 28.5 and 26.1%, respectively [17,18].
In our study, we compared the outcome of 64 DCD and 303 DBCD kidney transplant. Our results indicated the effect of DBCD was better than DCD in DGF and AR. The various indexes of donors and recipients including demography characteristics, index of renal function before donation, history of primary disease, HLA mismatches and dialysis were similar between DBCD and DCD groups. DBCD in our study is belonging to controlled DCD, while DCD is belonging to uncontrolled DCD. Therefore, it is easy to understand why the overall outcomes of DBCD are close to that for DBD and better than that for DCD. These data reflected that the real reason decided the good transplant effect was the processes of donation. The major underlying mechanism of DGF is related to ischaemia/reperfusion injury, which includes microvascular inflammation and cell death and apoptosis, and to the regeneration processes. Clinical factors related to donor, recipient and organ procurement/transplantation  procedures may increase the risk of DGF. Some of these parameters have been used in specific predictive formulas created to assess the risk of DGF [19]. The important finding of this study for the high risk factors of DGF after renal transplantation were history of hypertension, serum creatinine of donor before donation, and low blood pressure (BP < 80 mmHg). The incidence of DGF after renal transplantation in the present study was 27% in recipients whose grafts were recovered from donors with a history of hypertension of at least 5 years. For such donors, it is necessary to learn more about their history of anti hypertensive treatment and treatment outcomes, whether they suffered complications of hypertension, and its influence on renal function. The donor's final serum creatinine value was one of important proposed risk factors for DGF [20]. Multivariate logistic regression analysis in our study also showed that higher serum creatinine of donors (OR = 1.09, [95% CI, 1.03 to 1.16], p = 0.003) before donation was risk factors of DGF occurrence, which was identical with others reports.
Kidney is an organ of hypertransfusion and very sensitive to ischemia, while Low blood pressure results the insufficient of kidney blood flow volume, which will induce ischemia/reperfusion injury on kidney and clinically present as the DGF. In our study, the data of univariate analysis showed that donors experienced in hypotension (BP < 100 mmHg) would increase the risk of DGF for recipients. However, multivariate analysis data showed hypotension experience with blood pressure less than 80 mmHg became significant after all variables with P < 0.1 in the univariate analyses were included in one multivariate model, it could be due to lack of power. In brief, both univariate and multivariate analysis showed the lower of the blood pressure, the higher of the DGF risk. The vasopressor agents used in our study were vascular active pharmaceutical (dopamine, aramine, norepinephrine) to stabilize the donor's blood pressure. All of the pharmaceuticals have minimal impact on renal function. On the other hand, the vasopressor agents ensure the sufficient blood in organs before donation, which is benefit for the function recovery of graft after transplantation.
It was showed that cold ischemia time has a critical effect on the development of DGF. The two most widely used preservation buffers, University of Wisconsin (UW) and histidine-tryptophan-ketoglutarate (HTK) solutions, show similar efficacy in terms of DGF rates for most donor types [21,22]. Machine perfusion was introduced in the early days of solid organ transplantation to minimize the adverse effects of cold storage on retrieved organs. Lifeport has the role of evaluating the quality of kidney, removing residual blood clots, reducing perfusion resistance, protecting the kidney, so that reducing the occurrence of DGF [7,23].

Category III Controlled
Withdrawal of life-sustaining therapy III Organ donation after brain death followed by circulatory death (DBCD)

Category VI Uncontrolled Controlled
Cardiac arrest while life brain dead II Organ donation after cardiac death (DCD) a All the cases of DCD in our study were in-hospital Limitations of our study include, first, it's a retrospective study and some information of donors and recipients are collected incompletely, which could influence the occurrence of DGF and graft outcomes. Second, a variety of other clinical factors may also increase the risk of DGF, such as marked body mass index of the donor and recipient, potential drug nephrotoxicity, surgical problems and/ or hyperimmunization of the recipient [19]. It should be detected any significant differences in outcomes in DBCD recipients with and without DGF. Finally, DGF may decrease the long-term graft function, but reports on this effect are inconsistent [9,19]. So the longer-term impact of DGF in recipients of DBCD and DCD kidney transplants needs to be seen.

Conclusions
In conclusion, the clinical outcomes of DBCD kidney transplantation is better than DCD kidney transplantation. Successful implementation of DBCD and subsequent kidney transplantation requires an accurate and timely assessment and maintenance of the function of the donated organs. The main risk factors of DGF are donors who have a history of hypertension, serum creatinine of donor before donation, and low blood pressure of donor before donation.