The recovery of organs from uncontrolled donors after circulatory death (uDCD) in Maastricht categories II has been authorized in France since August 2005 and must be performed according to a national protocol.1 uDCD refers to donation from persons declared dead after an unsuccessfully resuscitated cardiac arrest. The protocol specifies that invasive techniques may be used for organ preservation after checking the national donation refusal registry but potentially before the family can confirm that the deceased person was not opposed to organ donation. In France between 2007 and 2014, we observed 895 potential uDCD donors, 414 actual uDCD donors, 814 recovered kidneys, 528 kidney transplants, and 315 utilized uDCD donors. In the utilized uDCD donors cohort, the probable or confirmed etiologies of cardiac arrest were sudden refractory cardiac arrest (without return of spontaneous circulation) in 70% of cases, asphyxiation in 8% of cases, and head injury in 6% of cases. The cause of death was sometimes readily apparent, but it could not be determined in 14% of cases.
The 2016 annual transplant report (Agence de la biomédecine) described transplant outcome according to donor type (standard donation after brain death [DBD], DBD extended criteria donor [ECD], and uDCD).2 ECD is defined by the American Organization of Transplantation and the United Network for Organ Sharing as donors aged 60 years or older or between 50 and 59 years old with at least 2 risk factors (donor hypertension, donor history of cerebrovascular accident, or terminal serum creatinine value >130 µmol/L).3 Primary nonfunction (PNF) rates were 3.1%, 5.3%, and 9.0%, 1-year graft failure rates were 5.7%, 12.5%, and 12.0%, and 1-year patient survival rates were 98.0%, 94.5%, and 96.9%, respectively.
To improve the management of uDCD and to assist the transplant community, we conducted a study of risk factors specific to uDCD to guide the decisions of the National Steering Committee. In the literature, cohorts of DCD mostly consist of controlled DCD, with little reference to uDCD.4-7 Furthermore, none of the published series met the criteria of our protocol. Risk factors impacting the posttransplant results of uDCD must be studied to evaluate the uDCD protocol and guide decisions. We measured the adjusted prognostic value of donor and recipient variables to identify risk factors for 2 different events:
- PNF of the graft, defined by immediate graft loss or renal allografts with delayed graft function (DGF) that failed to resolve by the end of the third month.
- Poor renal function at 1 year among patients without PNF, defined by either an estimated glomerular filtration rate (eGFR) <30 mL/min at 1 year or early graft loss (<1 y).
MATERIALS AND METHODS
This protocol is based on the observation that warm ischemia is a detrimental but unavoidable factor in situations of prolonged circulatory arrest. Experts have therefore defined the priority of limiting or banning other risk factors known to predispose to graft loss. This priority is the basis for the criteria used to select both donors and recipients, the maximum permissible ischemia times, and the choice of preservation techniques.1
- 1. Only uncontrolled donors after circulatory death and after failure of adequate cardiopulmonary resuscitation. Donor characteristics: age <55 years with no known vascular disease and no history of kidney failure, chronic hypertension, diabetes, or active neoplasms; exclusion of patients with multiple trauma resulting from high-energy kinetics with massive hemorrhage, which make both cardiac massage and organ perfusion after cannulation ineffective.
- 2. Functional warm ischemia time (fWIT): time from cardiac arrest to initiation of organ perfusion (ie, vessel cannulation after rapid laparotomy or initiation of normothermic regional perfusion [NRP]). No-flow time cannot exceed 30 minutes, and fWIT (no-flow + low-flow) cannot exceed 150 minutes. These duration estimates must be rigorous and imply the presence of a reliable witness to determine the precise time of collapse (Figure 1).
- 3. In situ preservation of abdominal organs:
- • Either at 4°C using in situ cooling (ISC), with a double-balloon triple-lumen catheter and an extracellular preservation solution including polyethylene glycol as colloid. The protocol imposed a maximum duration of 180 minutes between starting perfusion and explantation of the kidneys (Figure 1).
- • Or at 33–36°C using NRP with femoral cannulas connected to an extracorporeal membrane oxygenation device. Reperfusion was limited to the abdomen by a Fogarty catheter with a balloon inflated in the descending aorta. NRP duration was limited to a maximum of 240 minutes before cooling the abdominal organs to 4°C, with the same cannula. Organs were then explanted as usual (Figure 1).
- • Teams were able to use the in situ preservation modality of their choice. One center decided to use NRP based on the publications available at that time.5 In view of the good results obtained by this center,8 other centers also decided to use NRP. Consequently, only one center used NRP in 2008, but all centers used NRP in 2016.
- 4.Kidneys had to be preserved on hypothermic machine perfusion immediately after explantation on the basis of experimental data. The primary objective was to reduce the PNF rate by excluding grafts with very high intrarenal resistance after 4 hours on the machine, and the secondary objective was to improve graft reperfusion.1,9
- 5.Cold ischemia time (CIT) had to be <18 hours. When ISC was used, CIT corresponds to the time from cannulation in the donor to clamp release in the recipient. When NRP was used, CIT corresponds to the time from switch from normothermic to hypothermic perfusion in the donor to clamp release in the recipient (Figure 1).
- 6.Recipient characteristics: ≤65 years before 2012, then no age condition, first transplant nonimmunized patients, immunosuppression induction by polyclonal antibodies because of their effects on ischemia-reperfusion lesions, and their ability to delay the introduction of calcineurin inhibitors.
Recipients had to be registered on the national waiting list, had to have provided their written informed consent (registration on the DCD waiting list does not prevent the recipient from receiving a graft from a brain dead donor, DBD). Local attribution of both grafts was always preferred to ensure the shortest possible CIT.
Population and Data Source
Data were extracted from the French Transplant National Registry (CRISTAL), which is managed by the National Health Transplant Authority (Agence de la biomédecine) and prospectively collects demographic, clinical, and laboratory data for all organ transplant candidates and donors, as well as recipient outcomes. Data were recorded at registration, procurement, transplantation and annually thereafter, in each center. Patient death and graft loss were prospectively reported. Data collection is mandatory, and research technicians double check data completeness and accuracy. The study was conducted in accordance with French law: research studies based on the CRISTAL national registry are part of transplant assessment activity and do not require institutional review board approval.
This analysis included renal grafts from uDCD between 2007 and 2014. Dual kidney transplants (6 grafts) were excluded because of the bias associated with their different nephron masses. Six patients who died during the first 3 months posttransplant (mean 24.5 ± 19 d, range 1–49) with no report of PNF were also excluded because of the lack of sufficient data. This study therefore included 499 renal grafts.
The following donor and organ preservation method characteristics were considered: age, body mass index (BMI), no-flow time, low-flow time, fWIT, and the in situ perfusion modality used before explantation (ISC or NRP). The recipient characteristics were age at transplantation, cause of end-stage renal disease, BMI, duration on dialysis before transplantation, and waiting time. Transplant characteristics were CIT, year of transplant, human leukocyte antigen (HLA) compatibility, and side of graft (right/left kidney).
We calculated eGFR from the MDRD formula without ethnicity.
Poor renal function at 1 year among patient without PNF was assessed by the 1-year graft loss rate (all causes of graft failure and mortality) and the 1-year eGFR. We reviewed the distribution of 1-year eGFR with the clinician. We arbitrarily chose a cutoff of 30 mL/min to define poor renal function, corresponding to 12% of the population.
When the missing data rate was <5%, missing explanatory variables (dialysis, CIT, and HLA-DQ) were imputed. Fewer than 10 patients had inconsistent or incomplete information from dialysis to graft. When dialysis was indicated as “yes,” but the dialysis initiation date was missing, time on dialysis was imputed by the median. CIT was missing for <20 patients. CIT was calculated as the interval between initiation of cold perfusion after NRP and graft revascularization time when it was known. The median CIT for the transplant center was imputed for other missing CIT values. Fifteen recipients had a missing HLA-DQ type. Their DQ matching status was imputed by “1,” the most common mode (65% of the population).
The donor cause of death and the recipient comorbidities were not analyzed, because >20% of these data were missing. In the context of uDCD, death occurs suddenly and its cause is rarely identified.
Risk factors were studied in a logistic model by univariate and multivariate analysis. We used the restricted cubic spline for linearity test and continuous variable control. Multivariate analysis included all factors with P < 0.2 in univariate analysis and was determined with stepwise selection and reviewed for clinical significance. Because of different practices between centers (program start dates, volume of activity, and in situ perfusion modality), a sensitivity analysis was conducted to detect a possible center effect. A mixed model was used to identify centers that would significantly modify the results. When such a center was identified, the analysis was repeated after excluding this center.
Statistical analyses were performed with SAS software, guide 5.1 (SAS Institute, Inc., Cary, NC).
Table 1 summarizes the donor characteristics, and Table 2 summarizes the recipients characteristics. NRP was used for 47% of donors for a mean of 210 minutes (± 42), while the mean duration of ISC was 143 minutes (± 50). The mean total fWIT was 135 minutes (± 15), and the mean CIT was 14 hours (± 4). Use of NRP increased substantially during the study period; NRP was initially performed in a single center in January 2008, accounted for 9% of cases in 2008 and was then progressively generalized to account for 84% of all cases in 2014. Mean donor age was 42 years, and 89% were male. Mean recipient age was 48 years; 81% were male, and 15% had not previously undergone dialysis.
After excluding cases of PNF, the mean length of hospital stay was 22 days [95% confidence interval = (21; 23), minimum = 8, maximum = 55, 21 missing data]. After excluding cases of PNF, DGF was observed in 75.7% of cases (defined as the need for dialysis during the first wk, 34 missing data).
Analysis of Risk Factors for PNF
In this series of 499 transplants, PNF occurred in 37 of cases (7.4%) (Figure 2). PNF was caused by a vascular complication (thrombosis or bleeding) in 48% of cases, and the cause was not specified in the remaining cases. In univariate analysis, the risk factors with P < 0.2 were waiting time, donor age, graft side, transplant period, and HLA-DQ mismatch.
In multivariate analysis (Table 3), a significantly higher risk of PNF was observed for young donors (continuous variable, OR = 0.95 [0.92–0.98]) and according to transplant period, with PNF increasing in 2011–2012. Seventeen cases of PNF were during the 2011–2012 period: 7 in the ISC group and 10 in the NRP group. Mean donor age was 37 year, and the mean no-flow time was 7.5 minutes. Mean recipient age was 52 years, and mean CIT was 12 hours. A nonsignificant protective effect was observed for NRP (15 cases of PNF, 6%) compared with ISC (22 cases of PNF, 8.9%) (OR = 1.83 [0.78–4.25] and P = 0.16). The model had an area under the receiver operating characteristic (ROC) curve of 0.72.
Sensitivity analysis revealed a significant effect of the in situ perfusion modality (NRP or ISC) after exclusion of one center: increased risk with ISC compared with NRP (OR = 4.14 [1.22–14.0]). There was also a significant excess risk for young donors (continuous variable, OR = 0.94 [0.90–0.99]) (Table 3). This model had an area under the ROC curve of 0.74. In the center excluded from this analysis, 15 cases of PNF were observed in a series of 108 transplants, including 10 out of 32 transplants perfused with NRP and 5 out of 56 transplants flushed with ISC.
Donor age was not correlated with no-flow time (min), low-flow time (min), fWIT (min), NRP or ISC duration (min), or CIT. There was a significant positive correlation between donor age and BMI. Donors <35 years had a mean BMI of 24.9 and those ≥35 years had a mean BMI of 26.7. The correlation between donor age and cause of death could not be studied.
Analysis of Risk Factors for Poor Renal Function (eGFR < 30 mL/min) or Early Loss of Graft Function (Before 1 Y)
After excluding cases of PNF, another 66 grafts (14.3%) met the study criteria for poor renal function, with either eGFR < 30 mL/min at 1 year (57, 86.4% of 66 grafts with eGFR mean at 23 mL/min ± 5.7) or loss of graft function between 0 and 12 months (9, 13.6% of 66 grafts) (Figure 2). In univariate analysis, risk factors with P < 0.2 were BMI, in situ perfusion modality and duration of in situ perfusion, CIT, graft side, mismatches for HLA A, B, DR, and DQ, and transplant period.
In multivariate analysis (Table 4), the risk of graft failure or poor function was significantly higher for ISC versus NRP (OR = 2.57 [1.45–4.55]) and for high donor BMI (continuous, OR = 1.16 [1.09–1.23]). We observed 23 cases of poor renal function at 1 year in the NRP group (9.8%) versus 43 in the ISC group (19%). This model had an area under the ROC curve of 0.72.
The sensitivity analysis, which excluded the principal centers (7 of the 15 centers) one at a time, confirmed these results and showed no center effect.
Risk Factors for PNF
In the multivariate analysis including the sensitivity analysis, 3 factors increased the risk of PNF: in situ perfusion modality before organ recovery, donor age, and transplant period.
The donor age effect was fairly low (OR = 0.95) but surprising; paradoxically and unexpectedly, organs from younger donors were associated with a higher risk of PNF. However, donor age was not correlated with no-flow time, low-flow time, fWIT, in situ perfusion modality and its duration, or CIT. No explanation can be provided for this donor age effect. The exact cause of circulatory arrest or information about drug doses during resuscitation was not available in the database. In contrast with controlled donation, rapid implementation of measures designed to shorten warm and CIT in the context of uncontrolled donation means that some significant data are not available such as the cause of death.
The choice of ISC as modality of in vivo organ perfusion appeared to result in a higher rate of PNF (OR = 1.83), but this effect was only statistically significant in the sensitivity analysis that excluded one center because of a center effect.
Risk Factors for Poor Renal Function at 1 Year or Early Graft Loss (<1 Y)
After exclusion of the cases of PNF, high donor BMI and ISC (versus NRP) were associated with significantly higher risks of graft failure or poor function at 1 year (eGFR < 30 mL/min) in multivariate analysis. It was decided to exclude cases of PNF from the analysis based on the assumption that risk factors would be different.
The effect of donor BMI was relatively limited (OR = 1.2) and could be explained by the higher frequency of unknown metabolic and cardiovascular complications in donors with high BMI as well as by the greater technical difficulties involved in rapid cannulation.
ISC as a modality of in situ preservation, despite its advantages in terms of simplicity, significantly increased the risk of poor renal function at 1 year (OR = 2.6) (P = 0.001).
Interestingly, no correlation was observed between PNF rate or poor renal function at 1 year and more advanced donor age, no-flow time, or fWIT. The absence of correlation in this cohort could be explained by intentionally restrictive selection for these potential risk factors (age < 55 y, no-flow < 30 min, fWIT < 150 min), strictly followed by the participating centers. This finding can be interpreted as a post hoc validation of the patient selection criteria rather than the lack of impact of these well-known risk factors.
The advantages of NRP remain controversial. The superiority of NRP has not yet been formally demonstrated, as evidence is derived from flawed clinical trials, most often single-center and nonrandomized trials,5,8,10 and limited experimental evidence.11-15 However, this technique not only provides better results, but also allows a more relaxed and less stressful procedure with a lower risk of iatrogenic injury.8,10
Together with the Spanish study,4 this retrospective study is the largest study to date, comprising 499 kidney transplantations performed in 15 centers. It provides new evidence in favor of NRP, although the beneficial effects of NRP have not yet been fully elucidated. Experimental work by the Barcelona group14 and the study by del Rio et al4 suggested a similar effect to that of ischemic preconditioning. Using a porcine liver transplantation model, this group showed that NRP increases adenosine levels and decreases xanthine levels in the liver parenchyma. This mechanism, described in the liver, may therefore apply to the whole body, with cardiac arrest mimicking clamping phases and NRP mimicking unclamping phases. NRP may therefore protect organs from severe ischemia-reperfusion injuries, thereby reducing the extent of the resulting fibrosis.
Two French groups have studied the extent of interstitial fibrosis in uDCD transplants, as fibrosis occurs as a result of inadequate healing of severe tubular necrosis and can be observed on biopsies within 3 months. Hanf et al16 found that 3- and 12-month posttransplant fibrosis rates were similar in uDCD and DBD-ECD grafts, although DCDs were younger. The fact that all uDCD grafts were initially flushed at 4°C suggests that this method is not optimal.16 Identifying more borderline acute rejection lesions, with more infiltrates in uDCD, the authors considered that these findings, together with poor HLA matching, justified induction with polyclonal antibodies. Viglietti et al6 also noted the important role of extensive postischemic fibrosis on graft outcome, with accelerated fibrosis and poorer renal function (eGFR) in the uDCD group compared to the DBD group, but only for DCD with an initial no-flow time > 2 minutes.6
Analysis of results by center showed that in the center with the most extensive NRP experience, uDCD kidney graft survival was equivalent to that DBD SCD (and not ECD), as reported by the Madrid team.8 Early recovery of graft function was observed more rapidly for NRP grafts than for ISC grafts.4,8 Other authors have reported similar experiences.7,10,17 Oniscu et al17 analyzed the use of NRP in 21 multiorgan procurements from controlled DCD in 3 UK centers and concluded that NRP improved graft outcome and facilitated organization of the whole procedure. del Rio et al4observed an increased risk of PNF, DGF, and graft failure at 1 year with ISC versus NRP. For all these reasons, when considering extension of the French national protocol to liver transplantation, it was decided to make NRP mandatory.18
Kidney transplantation from uDCD has been authorized in France since August 2005 and must be performed according to a nationwide protocol established by specialists in the field and the National Health Transplant Authority (Agence de la biomédecine).1 Despite a much higher rate of PNF from uDCD, transplant outcomes were similar to those from DBD ECD,1 which could be due to strict donor selection, limited ischemia time and the use of NRP. These results could be further improved by shortening fWIT, and the assessment of the quality normothermic perfusion by means of new biomarkers or ultrasound techniques. Multivariate analysis of French data showed a negative impact of high-BMI donors and a beneficial effect of oxygenated normothermic recirculation, with NRP playing a protective role. Most centers have chosen NRP as the preferred in situ perfusion modality. This approach should help to prevent or limit fibrosis associated with ischemia-reperfusion injury as well as the extent of initial tubular necrosis. As in Spain, but in contrast with many other countries, France has initiated an uncontrolled DCD program. Because of its high consumption of resources (material and staff) and time, it has a limited effect on organ shortage. It was therefore decided to initiate a controlled DCD program, which has a substantial potential to enlarge the donor pool and reduce the organ shortage. The experience accumulated during the first phase of “uDCD only” was very helpful, and all teams participating in the cDCD program have chosen to use NRP to perfuse abdominal organs.
This program requires optimal organization and a high level of motivation by all stakeholders. It would never have seen the day or been successful without the help of all of SAMU, intensive care unit, and hospital liver and kidney graft coordination unit professionals at the pilot sites: CHU Ed. Herriot Lyon, CHU Strasbourg, CHU Nancy, CHU d’Angers, CHU Nantes, RHC Annecy, CHU Rouen, APHP St Louis, APHP Pitié, APHP Bicêtre, APHP Henri Mondor, and CHU Lille. The National Steering Committee of Donation After Circulatory Death is from Agence de la biomédecine, Saint Denis, France
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18. Savier E, Dondero F, Vibert E, et al; Donation After Cardiac Death Study Group. First experience of liver transplantation with type 2 donation after cardiac death in france. Liver Transpl. 2015; 21:631–643