Does Normothermic Regional Perfusion Improve the Results of Donation After Circulatory Death Liver Transplantation?

US Liver Transplant Outcomes After Normothermic Regional Perfusion vs Standard Super Rapid Recovery

Importance

Normothermic regional perfusion (NRP) is an emerging recovery modality for transplantable allografts from controlled donation after circulatory death (cDCD) donors. In the US, only 11.4% of liver recipients who are transplanted from a deceased donor receive a cDCD liver. NRP has the potential to safely expand the US donor pool with improved transplant outcomes as compared with standard super rapid recovery (SRR).

Objective

To assess outcomes of US liver transplants using controlled donation after circulatory death livers recovered with normothermic regional perfusion vs standard super rapid recovery.

Design, Setting, and Participants

This was a retrospective, observational cohort study comparing liver transplant outcomes from cDCD donors recovered by NRP vs SRR. Outcomes of cDCD liver transplant from January 2017 to May 2023 were collated from 17 US transplant centers and included livers recovered by SRR and NRP (thoracoabdominal NRP [TA-NRP] and abdominal NRP [A-NRP]). Seven transplant centers used NRP, allowing for liver allografts to be transplanted at 17 centers; 10 centers imported livers recovered via NRP from other centers.

Exposures

cDCD livers were recovered by either NRP or SRR.

Main Outcomes and Measures

The primary outcome was ischemic cholangiopathy (IC). Secondary end points included primary nonfunction (PNF), early allograft dysfunction (EAD), biliary anastomotic strictures, posttransplant length of stay (LOS), and patient and graft survival.

Results

A total of 242 cDCD livers were included in this study: 136 recovered by SRR and 106 recovered by NRP (TA-NRP, 79 and A-NRP, 27). Median (IQR) NRP and SRR donor age was 30.5 (22-44) years and 36 (27-49) years, respectively. Median (IQR) posttransplant LOS was significantly shorter in the NRP cohort (7 [5-11] days vs 10 [7-16] days; P < .001). PNF occurred only in the SRR allografts group (n = 2). EAD was more common in the SRR cohort (123 of 136 [56.1%] vs 77 of 106 [36.4%]; P = .007). Biliary anastomotic strictures were increased 2.8-fold in SRR recipients (7 of 105 [6.7%] vs 30 of 134 [22.4%]; P = .001). Only SRR recipients had IC (0 vs 12 of 133 [9.0%]; P = .002); IC-free survival by Kaplan-Meier was significantly improved in NRP recipients. Patient and graft survival were comparable between cohorts.

Conclusion and Relevance

There was comparable patient and graft survival in liver transplant recipients of cDCD donors recovered by NRP vs SRR, with reduced rates of IC, biliary complications, and EAD in NRP recipients. The feasibility of A-NRP and TA-NRP implementation across multiple US transplant centers supports increasing adoption of NRP to improve organ use, access to transplant, and risk of wait-list mortality.

OXIDATIVE study: A pilot prospective observational cohort study protocol examining the influence of peri-reperfusion hyperoxemia and immune dysregulation on early allograft dysfunction after orthotopic liver transplantation

Early allograft dysfunction (EAD) is a functional hepatic insufficiency within a week of orthotopic liver transplantation (OLT) and is associated with morbidity and mortality. The etiology of EAD is multifactorial and largely driven by ischemia reperfusion injury (IRI), a phenomenon characterized by oxygen scarcity followed by paradoxical oxidative stress and inflammation. With the expanded use of marginal allografts more susceptible to IRI, the incidence of EAD may be increasing. This necessitates an in-depth understanding of the innate molecular mechanisms underlying EAD and interventions to mitigate its impact. Our central hypothesis is peri-reperfusion hyperoxemia and immune dysregulation exacerbate IRI and increase the risk of EAD. We will perform a pilot prospective single-center observational cohort study of 40 patients. The aims are to determine (1) the association between peri-reperfusion hyperoxemia and EAD and (2) whether peri-reperfusion perturbed cytokine, protein, and hypoxia inducible factor-1 alpha (HIF-1α) levels correlate with EAD after OLT. Inclusion criteria include age ≥ 18 years, liver failure, and donation after brain or circulatory death. Exclusion criteria include living donor donation, repeat OLT within a week of transplantation, multiple organ transplantation, and pregnancy. Partial pressure of arterial oxygen (PaO2) as the study measure allows for the examination of oxygen exposure within the confines of existing variability in anesthesiologist-administered fraction of inspired oxygen (FiO2) and the inclusion of patients with intrapulmonary shunting. The Olthoff et al. definition of EAD is the primary outcome. Secondary outcomes include postoperative acute kidney injury, pulmonary and biliary complications, surgical wound dehiscence and infection, and mortality. The goal of this study protocol is to identify EAD contributors that could be targeted to attenuate its impact and improve OLT outcomes. If validated, peri-reperfusion hyperoxemia and immune perturbations could be targeted via FiO2 titration to a goal PaO2 and/or administration of an immunomodulatory agent by the anesthesiologist intraoperatively.

Intraoperative Anesthetic Strategies to Mitigate Early Allograft Dysfunction After Orthotopic Liver Transplantation: A Narrative Review

Orthotopic liver transplantation (OLT) is the most effective treatment for patients with end-stage liver disease (ESLD). Hepatic insufficiency within a week of OLT, termed early allograft dysfunction (EAD), occurs in 20% to 25% of deceased donor OLT recipients and is associated with morbidity and mortality. Primary nonfunction (PNF), the most severe form of EAD, leads to death or retransplantation within 7 days. The etiology of EAD is multifactorial, including donor, recipient, and surgery-related factors, and largely driven by ischemia-reperfusion injury (IRI). IRI is an immunologic phenomenon characterized by dysregulation of cellular oxygen homeostasis and innate immune defenses in the allograft after temporary cessation (ischemia) and later restoration (reperfusion) of oxygen-rich blood flow. The rising global demand for OLT may lead to the use of marginal allografts, which are more susceptible to IRI, and thus lead to an increased incidence of EAD. It is thus imperative the anesthesiologist is knowledgeable about EAD, namely its pathophysiology and intraoperative strategies to mitigate its impact. Intraoperative strategies can be classified by 3 phases, specifically donor allograft procurement, storage, and recipient reperfusion. During procurement, the anesthesiologist can use pharmacologic preconditioning with volatile anesthetics, consider preharvest hyperoxemia, and attenuate the use of norepinephrine as able. The anesthesiologist can advocate for normothermic regional perfusion (NRP) and machine perfusion during allograft storage at their institution. During recipient reperfusion, the anesthesiologist can optimize oxygen exposure, consider adjunct anesthetics with antioxidant-like properties, and administer supplemental magnesium. Unfortunately, there is either mixed, little, or no data to support the routine use of many free radical scavengers. Given the sparse, limited, or at times conflicting evidence supporting some of these strategies, there are ample opportunities for more research to find intraoperative anesthetic strategies to mitigate the impact of EAD and improve postoperative outcomes in OLT recipients.

Strategies to Improve the Utilization and Function of DCD Livers

Despite the increased usage of livers from donation after circulatory death (DCD) donors in the last decade, many patients remaining on the waitlist who need a liver transplant. Recent efforts have focused on maximizing the utilization and outcomes of these allografts using advances in machine perfusion technology and other perioperative strategies such as normothermic regional perfusion (NRP). In addition to the standard donor and recipient matching that is required with DCD donation, new data regarding the impact of graft steatosis, extensive European experience with NRP, and the increasing use of normothermic and hypothermic machine perfusion have shown immense potential in increasing DCD organ overall utilization and improved outcomes. These techniques, along with viability testing of extended criteria donors, have generated early promising data to consider the use of higher-risk donor organs and more widespread adoption of these techniques in the United States. This review explores the most recent international literature regarding strategies to optimize the utilization and outcomes of DCD liver allografts, including donor-recipient matching, perioperative strategies including NRP versus rapid controlled DCD recovery, viability assessment of discarded livers, and postoperative strategies including machine perfusion versus pharmacologic interventions.

Mitochondrial injury during normothermic regional perfusion (NRP) and hypothermic oxygenated perfusion (HOPE) in a rodent model of DCD liver transplantation

BACKGROUND

Normothermic regional perfusion (NRP) and hypothermic-oxygenated-perfusion (HOPE), were both shown to improve outcomes after liver transplantation from donors after circulatory death (DCD). Comparative clinical and mechanistical studies are however lacking.

METHODS

A rodent model of NRP and HOPE, both in the donor, was developed. Following asystolic donor warm ischemia time (DWIT), the abdominal compartment was perfused either with a donor-blood-based-perfusate at 37 °C (NRP) or with oxygenated Belzer-MPS at 10 °C (donor-HOPE) for 2 h. Livers were then procured and underwent 5 h static cold storage (CS), followed by transplantation. Un-perfused and HOPE-treated DCD-livers (after CS) and healthy livers (DBD) with direct implantation after NRP served as controls. Endpoints included the entire spectrum of ischemia-reperfusion-injury.

FINDINGS

Healthy control livers (DBD) showed minimal signs of inflammation during 2 h NRP and achieved 100% posttransplant recipient survival. In contrast, DCD livers with 30 and 60 min DWIT suffered from greater mitochondrial injury and inflammation as measured by increased perfusate Lactate, FMN- and HMGB-1-levels with subsequent Toll-like-receptor activation during NRP. In contrast, donor-HOPE (instead of NRP) led to significantly less mitochondrial-complex-I-injury and inflammation. Results after donor-HOPE were comparable to ex-situ HOPE after CS. Most DCD-liver recipients survived when treated with one HOPE-technique (86%), compared to only 40% after NRP (p = 0.0053). Following a reduction of DWIT (15 min), DCD liver recipients achieved comparable survivals with NRP (80%).

INTERPRETATION

High-risk DCD livers benefit more from HOPE-treatment, either immediately in the donor or after cold storage. Comparative prospective clinical studies are required to translate the results.

FUNDING

Funding was provided by the Swiss National Science Foundation (grant no: 32003B-140776/1, 3200B-153012/1, 320030-189055/1, and 31IC30-166909) and supported by University Careggi (grant no 32003B-140776/1) and the OTT (grant No.: DRGT641/2019, cod.prog. 19CT03) and the Max Planck Society. Work in the A.G. laboratory was partially supported by the NIH R01NS112381 and R21NS125466 grants.

Viability assessment of livers donated after circulatory determination of death during normothermic regional perfusion

BACKGROUND

Abdominal normothermic regional perfusion (A-NRP) allows in-situ reperfusion and recovery of abdominal organs metabolism in donors after circulatory death (DCD). Besides improving liver transplantation outcomes, liver injury and function can be assessed during A-NRP.

METHODS

To refine liver viability assessment during A-NRP, prospectively collected data of controlled DCD donors managed at our Institution between October 2019 and May 2022 were retrospectively analyzed. Baseline characteristics, procedural variables and A-NRP parameters of donors whose liver was successfully transplanted were compared to those of donors whose liver was discarded.

RESULTS

Twenty-seven donors were included and in 20 (74%) the liver was accepted (positive outcome). No differences between study groups were observed concerning baseline characteristics and warm ischemia times (WIT). Initial lactate levels were positively correlated with functional WIT (r2  = 0.4, p = 0.04), whereas transaminase levels were not. Blood flow during A-NRP was comparable, whereas oxygen consumption (VO2 ) was significantly higher in the positive outcome group after 1 h. Time courses of lactate, AST and ALT were significantly different between study groups (p < 0.001). Donors whose liver was accepted showed faster lactate clearance, a difference which was amplified by normalizing lactate clearance to oxygen delivery (DO2 ) and VO2 . Lactate clearance was correlated to transaminase levels and DO2 -normalized lactate clearance was the parameter best discriminating between study groups.

CONCLUSIONS

DO2 -normalized lactate clearance may represent an element of liver viability assessment during A-NRP.

Acute rejection after liver transplantation with machine perfusion versus static cold storage: A systematic review and meta-analysis

BACKGROUND AND AIMS

Acute cellular rejection (ACR) is a frequent complication after liver transplantation. By reducing ischemia and graft damage, dynamic preservation techniques may diminish ACR. We performed a systematic review to assess the effect of currently tested organ perfusion (OP) approaches versus static cold storage (SCS) on post-transplant ACR-rates.

APPROACH AND RESULTS

A systematic search of Medline, Embase, Cochrane Library, and Web of Science was conducted. Studies reporting ACR-rates between OP and SCS and comprising at least 10 liver transplants performed with either hypothermic oxygenated perfusion (HOPE), normothermic machine perfusion, or normothermic regional perfusion were included. Studies with mixed perfusion approaches were excluded. Eight studies were identified (226 patients in OP and 330 in SCS). Six studies were on HOPE, one on normothermic machine perfusion, and one on normothermic regional perfusion. At meta-analysis, OP was associated with a reduction in ACR compared with SCS [OR: 0.55 (95% CI, 0.33-0.91), p =0.02]. This effect remained significant when considering HOPE alone [OR: 0.54 (95% CI, 0.29-1), p =0.05], in a subgroup analysis of studies including only grafts from donation after cardiac death [OR: 0.43 (0.20-0.91) p =0.03], and in HOPE studies with only donation after cardiac death grafts [OR: 0.37 (0.14-1), p =0.05].

CONCLUSIONS

Dynamic OP techniques are associated with a reduction in ACR after liver transplantation compared with SCS. PROSPERO registration: CRD42022348356.

An extensive evaluation of hepatic markers of damage and regeneration in controlled and uncontrolled donation after circulatory death

Livers from donations after circulatory death (DCDs) are very sensitive to ischemia/reperfusion injury and thus need careful reconditioning, such as normothermic regional perfusion (NRP). So far, its impact on DCDs has not been thoroughly investigated. This pilot cohort study aimed to explore the NRP impact on liver function by evaluating dynamic changes of circulating markers and hepatic gene expression in 9 uncontrolled DCDs (uDCDs) and 10 controlled DCDs. At NRP start, controlled DCDs had lower plasma levels of inflammatory and liver damage markers, including α-glutathione s-transferase, sorbitol-dehydrogenase, malate dehydrogenase 1, liver-type arginase-1, and keratin-18, but higher levels of osteopontin, sFas, flavin mononucleotide, and succinate than uDCDs. During 4-hour NRP, some damage and inflammatory markers increased in both groups, while IL-6, HGF, and osteopontin increased only in uDCDs. At the NRP end, the tissue expression of early transcriptional regulators, apoptosis, and autophagy mediators was higher in uDCDs than in controlled DCDs. In conclusion, despite initial differences in liver damage biomarkers, the uDCD group was characterized by a major gene expression of regenerative and repair factors after the NRP procedure. Correlative analysis among circulating/tissue biomarkers and the tissue congestion/necrosis degree revealed new potential candidate biomarkers.

Machine perfusion and the prevention of ischemic type biliary lesions following liver transplant: What is the evidence?

The widespread uptake of different machine perfusion (MP) strategies for liver transplant has been driven by an effort to minimize graft injury. Damage to the cholangiocytes during the liver donation, preservation, or early posttransplant period may result in stricturing of the biliary tree and inadequate biliary drainage. This problem continues to trouble clinicians, and may have catastrophic consequences for the graft and patient. Ischemic injury, as a result of compromised hepatic artery flow, is a well-known cause of biliary strictures, sepsis, and graft failure. However, very similar lesions can appear with a patent hepatic artery and these are known as ischemic type biliary lesions (ITBL) that are attributed to microcirculatory dysfunction rather than main hepatic arterial compromise. Both the warm and cold ischemic period duration appear to influence the onset of ITBL. All of the commonly used MP techniques deliver oxygen to the graft cells, and therefore may minimize the cholangiocyte injury and subsequently reduce the incidence of ITBL. As clinical experience and published evidence grows for these modalities, the impact they have on ITBL rates is important to consider. In this review, the evidence for the three commonly used MP strategies (abdominal normothermic regional perfusion [A-NRP], hypothermic oxygenated perfusion [HOPE], and normothermic machine perfusion [NMP] for ITBL prevention has been critically reviewed. Inconsistencies with ITBL definitions used in trials, coupled with variations in techniques of MP, make interpretation challenging. Overall, the evidence suggests that both HOPE and A-NRP prevent ITBL in donated after circulatory death grafts compared to cold storage. The evidence for ITBL prevention in donor after brain death grafts with any MP technique is weak.

How to improve results after DCD (donation after circulation death)

The shortage of organs for transplantation has led health professionals to look for alternative sources of donors. One of the avenues concerns donors who have died after circulatory arrest. This is a special situation because the organs from these donors are exposed to warm ischaemia-reperfusion lesions that are unavoidable during the journey of the organs from the donor to the moment of transplantation in the recipient. We will address and discuss the key issues from the perspective of team organization, legislation and its evolution, and the ethical framework. In a second part, the avenues to improve the quality of organs will be presented following the itinerary of the organs between the donor and the recipient. The important moments from the point of view of therapeutic strategy will be put into perspective. New connections between key players involved in pathophysiological mechanisms and implications for innate immunity and injury processes are among the avenues to explore. Technological developments to improve the quality of organs from these recipients will be analyzed, such as perfusion techniques with new modalities of temperatures and oxygenation. New molecules are being investigated for their potential role in protecting these organs and an analysis of potential prospects will be proposed. Finally, the important perspectives that seem to be favored will be discussed in order to reposition the use of deceased donors after circulatory arrest. The use of these organs has become a routine procedure and improving their quality and providing the means for their evaluation is absolutely inevitable.

Does machine perfusion improve immediate and short-term outcomes by enhancing graft function and recipient recovery after liver transplantation? A systematic review of the literature, meta-analysis and expert panel recommendations

BACKGROUND

Recent evidence supports the use of machine perfusion technologies (MP) for marginal liver grafts. Their effect on enhanced recovery, however, remains uncertain.

OBJECTIVES

To identify areas in which MP might contribute to an ERAS program and to provide expert panel recommendations.

DATA SOURCES

Ovid MEDLINE, Embase, Scopus, Google Scholar, and Cochrane Central.

METHODS

Systematic review and meta-analysis following PRISMA guidelines and recommendations using the GRADE approach. CRD42021237713 RESULTS: Both hypothermic (HMP) and normothermic (NMP) machine perfusion demonstrated significant benefits in preventing postreperfusion syndrome (PRS) (HMP OR .33, .15-.75 CI; NMP OR .51, .29-.90 CI) and early allograft dysfunction (EAD) (HMP OR .51, .35-.75 CI; NMP OR .66, .45-.97 CI), while shortening LOS (HMP MD -3.9; NMP MD -12.41). Only NMP showed a significant decrease in the length of ICU stay (L-ICU) (MD -7.07, -8.76; -5.38 CI), while only HMP diminishes the likelihood of major complications. Normothermic regional perfusion (NRP) reduces EAD (OR .52, .38-.70 CI) and primary nonfunction (PNF) (OR .51, .27-.98 CI) without effect on L-ICU and LOS.

CONCLUSIONS

The use of HMP decreases PRS and EAD, specifically for marginal grafts. This is supported by a shorter LOS and a lower rate of major postoperative complications (QOE; moderate | Recommendation; Strong). NMP reduces the incidence of PRS and EAD with associated shortening in L-ICU for both DBD and DCD grafts (QOE; moderate | Recommendation; High) This technology also shortens the length of hospital stay (QOE; low | Recommendation; Strong). NRP decreases the likelihood of EAD (QOE; moderate) and the risk of PNF (QOE; low) when compared to both DBD and SRR-DCD grafts preserved in SCS. (Recommendation; Strong).

Machine Perfusion for Extended Criteria Donor Livers: What Challenges Remain?

Based on the renaissance of dynamic preservation techniques, extended criteria donor (ECD) livers reclaimed a valuable eligibility in the transplantable organ pool. Being more vulnerable to ischemia, ECD livers carry an increased risk of early allograft dysfunction, primary non-function and biliary complications and, hence, unveiled the limitations of static cold storage (SCS). There is growing evidence that dynamic preservation techniques—dissimilar to SCS—mitigate reperfusion injury by reconditioning organs prior transplantation and therefore represent a useful platform to assess viability. Yet, a debate is ongoing about the advantages and disadvantages of different perfusion strategies and their best possible applications for specific categories of marginal livers, including organs from donors after circulatory death (DCD) and brain death (DBD) with extended criteria, split livers and steatotic grafts. This review critically discusses the current clinical spectrum of livers from ECD donors together with the various challenges and posttransplant outcomes in the context of standard cold storage preservation. Based on this, the potential role of machine perfusion techniques is highlighted next. Finally, future perspectives focusing on how to achieve higher utilization rates of the available donor pool are highlighted.

Liver perfusion strategies: what is best and do ischemia times still matter?

PURPOSE OF REVIEW

This review describes recent developments in the field of liver perfusion techniques.

RECENT FINDINGS

Dynamic preservation techniques are increasingly tested due to the urgent need to improve the overall poor donor utilization. With their exposure to warm ischemia, livers from donors after circulatory death (DCD) transmit additional risk for severe complications after transplantation. Although the superiority of dynamic approaches compared to static-cold-storage is widely accepted, the number of good quality studies remains limited. Most risk factors, particularly donor warm ischemia, and accepted thresholds are inconsistently reported, leading to difficulties to assess the impact of new preservation technologies. Normothermic regional perfusion (NRP) leads to good outcomes after DCD liver transplantation, with however short ischemia times. While randomized controlled trials (RCT) with NRP are lacking, results from the first RCTs with ex-situ perfusion were reported. Hypothermic oxygenated perfusion was shown to protect DCD liver recipients from ischemic cholangiopathy. In contrast, endischemic normothermic perfusion seems to not impact on the development of biliary complications, although this evidence is only available from retrospective studies.

SUMMARY

Dynamic perfusion strategies impact posttransplant outcomes and are increasingly commissioned in various countries along with more evidence from RCTs. Transparent reporting of risk and utilization with uniform definitions is required to compare the role of different preservation strategies in DCD livers with prolonged ischemia times.

Outcome of Liver Transplants Using Donors After Cardiac Death With Normothermic Regional Perfusion

BACKGROUND AND AIMS

The incorporation of normothermic regional perfusion (NRP) to donors after cardiac death (DCD) allows the recovery of liver grafts without the deleterious effects on graft survival the super-rapid technique may cause. The aim of the present report is to determine if the use of NRP in Maastricht type III DCD donors achieves short- and medium-term results comparable to donors after brain death (DBD).

PATIENTS AND METHODS

This is an observational cohort study including 117 liver transplants executed between November 2016 and April 2021, divided into NRP (n = 39) and DBD (n = 78).

RESULTS

Donors were younger in the NRP group (NRP 52 vs DBD 59.4 years; P < .005). Liver recipients in each study group were of similar age and severity of liver disease, although the predominant transplant indication in the NRP group was hepatocellular carcinoma. No differences in ischemia times were found. The incidence of early allograft disfunction and primary nonfunction was balanced between NRP and DBD. Eight patients required retransplant, all of them in the DBD group. No differences were found in biliary complications (NRP 12% vs DBD 5%; P = .104). Ischemic cholangiopathy affected a single DBD patient. Graft survival's Kaplan Meier curve shows a better outcome in the NRP group, although the difference did not reach significance (P = .075).

CONCLUSIONS

The incorporation of perfusion machines, and specifically the NPR in situ, converts suboptimal liver grafts such as DCD into organs comparable to DBDs.

A systematic review and meta-analyses of regional perfusion in donation after circulatory death solid organ transplantation

In donation after circulatory death (DCD), (thoraco)abdominal regional perfusion (RP) restores circulation to a region of the body following death declaration. We systematically reviewed outcomes of solid organ transplantation after RP by searching PubMed, Embase, and Cochrane libraries. Eighty-eight articles reporting on outcomes of liver, kidney, pancreas, heart, and lung transplants or donor/organ utilization were identified. Meta-analyses were conducted when possible. Methodological quality was assessed using National Institutes of Health (NIH)-scoring tools. Case reports (13/88), case series (44/88), retrospective cohort studies (35/88), retrospective matched cohort studies (5/88), and case-control studies (2/88) were identified, with overall fair quality. As blood viscosity and rheology change below 20 °C, studies were grouped as hypothermic (HRP, ≤20 °C) or normothermic (NRP, >20 °C) regional perfusion. Data demonstrate that RP is a safe alternative to in situ cold preservation (ISP) in uncontrolled and controlled DCDs. The scarce HRP data are from before 2005. NRP appears to reduce post-transplant complications, especially biliary complications in controlled DCD livers, compared with ISP. Comparisons for kidney and pancreas with ISP are needed but there is no evidence that NRP is detrimental. Additional data on NRP in thoracic organs are needed. Whether RP increases donor or organ utilization needs further research.