Extended criteria brain-dead organ donors:Prevalence and impact on the utilisation of livers for transplantation in Brazil

BACKGROUND Despite its association with higher postoperative morbidity and mortality,the use of extended criteria donor(ECD)livers for transplantation has increased globally due to the high demand for the procedure.AIM To investigate the prevalence of ECD in donation after brain death(DBD)and its impact on organ acceptance for transplantation.METHODS Retrospective analysis of DBD organ offers for liver transplantation between 2017 and 2020 in a high-volume transplant centre.The incidence of the Eurotransplant risk factors to define an ECD(ET-ECD)among DBD donors and the likelihood of organ acceptance over the years were analysed.The relationship between organ refusal for transplantation,the occurrence,and the number of ET-ECD was assessed by simple and multiple logistic regression adjustment.RESULTS A total of 1619 organ donors were evaluated.Of these,78.31%(n=1268)had at least one ET-ECD criterion.There was an increase in the acceptance of ECD DBD organs for transplantation(1 criterion:from 23.40%to 31.60%;2 criteria:from 13.10%to 27.70%;3 criteria:From 6.30%to 13.60%).For each addition of one ETECD variable,the estimated chance of organ refusal was 64.4%higher(OR 1.644,95%CI 1.469-1.839,P<0.001).Except for the donor serum sodium>165 mmol/L(P=0.310),all ET-ECD criteria increased the estimated chance of organ refusal for transplantation.CONCLUSION A high prevalence of ECD DBD was observed.Despite the increase in their utilisation,the presence and the number of extended donor criteria were associated with an increased likelihood of their refusal for transplantation.

Exercise training as an intervention for frailty in cirrhotic patients on the liver transplant waiting list:A systematic review

BACKGROUND The existing literature suggests that exercise for cirrhotic patients is safe and favours significant improvement to their physical capacity.However,exercise training for this population and how to deliver activities,especially in severe stages of the disease and while waiting for a liver transplant(LT),remain undefined.AIM To review the existing exercise prescriptions for cirrhotic patients on the waiting list for LT,their results for frailty evolution and their effect on clinical outcomes.METHODS A systematic review was performed following the Preferred Reporting Review and Meta-Analysis guidelines and searching the PubMed,MEDLINE,and Scopus databases.The keyword“liver transplant”was used in combination with the free terms“frailty”and“exercise”for the literature review.Clinical studies that evaluated the effect of a regular training program,independent of supervision or the duration or intensity of physical exercise,in cirrhotic patients on the waiting list for LT were reviewed.The data on safe physical activity prescriptions following Frequency,Intensity,Time,and Type recommendations were extracted and summarised.RESULTS Nine articles met the inclusion criteria for this review.Various instruments for frailty assessment were used,frequently in combination.Five studies prescribed physical activity for patients,one in-person and four to be performed remotely and unsupervised.The remaining four studies only used a self-report instrument to assess the level of physical activity.None reported adverse events related to exercise training.The exercise frequency mainly varied from daily to a minimum of twice per week.The intensity depended on frailty and included increasing levels of activity.The type of exercise was predominantly a combination of aerobic and resistance training.The duration of exercise varied from 4 to 12 wk.Three articles evaluated the effect of the exercise program on clinical outcomes,reporting a reduction in 90-d readmission rates post-transplant and improved frailty scores,as well as improved survival of cirrhotic patients waiting for LT.CONCLUSION Routine frailty assessment is essential for this population.Although more robust evidence is required,the prescription of exercise is safe and can improve patients’functional capacity,improving pre-and post-LT outcomes.

Mechanisms of autophagy activation in endothelial cell and their targeting during normothermic machine liver perfusion

Ischaemia-reperfusion injury(IRI) is the leading cause of injury seen in the liver following transplantation. IRI also causes injury following liver surgery and haemodynamic shock. The first cells within the liver to be injured by IRI are the liver sinusoidal endothelial cells(LSEC). Recent evidence suggests that LSEC coordinate and regulates the livers response to a variety of injuries. It is becoming increasingly apparent that the cyto-protective cellular process of autophagy is a key regulator of IRI. In particular LSEC autophagy may be an essential gatekeeper to the development of IRI. The recent availability of liver perfusion devices has allowed for the therapeutic targeting of autophagy to reduce IRI. In particular normothermic machine liver perfusion(NMP-L) allow the delivery of pharmacological agents to donor livers whilst maintaining physiological temperature and hepatic flow rates. In this review we summarise the current understanding of endothelial autophagy and how this may be manipulated during NMP-L to reduce liver IRI.

Update on the management and treatment of viral hepatitis

This review aims to summarize the current evidence on the treatment of viral hepatitis,focusing on its clinical management.Also,future treatment options and areas of potential research interest are detailed.PubMed and Scopus databases were searched for primary studies published within the last ten years.Keywords included hepatitis A virus,hepatitis B virus(HBV),hepatitis C virus,hepatitis D virus(HDV),hepatitis E virus,and treatment.Outcomes reported in the studies were summarized,tabulated,and synthesized.Significant advances in viral hepatitis treatment were accomplished,such as the advent of curative therapies for hepatitis C and the development and improvement of hepatitis A,hepatitis B,and hepatitis E vaccination.Drugs that cure hepatitis B,going beyond viral suppression,are so far unavailable;however,targeted antiviral drugs against HBV(immunomodulatory therapies and gene silencing technologies)are promising approaches to eradicating the virus.Ultimately,high vaccination coverage and large-scale test-and-treat programmes with high screening rates may eliminate viral hepatitis and mitigate their burden on health systems.The development of curative hepatitis C treatment renewed the enthusiasm for curing hepatitis B,albeit further investigation is required.Novel therapeutic options targeting HDV life cycle are currently under clinical investigation.

Machine perfusion of the liver: Which is the best technique to mitigate ischaemia-reperfusion injury?

Longstanding research describes the mechanisms whereby the restoration of blood flow and reoxygenation(reperfusion) aggravates the ischaemic injury caused by a period of anoxia to a donor liver. This phenomenon, called ischaemia-reperfusion injury(IRI), leads to parenchymal cell death,microcirculatory failure, and inflammatory immune response. Clinically, IRI is the main factor responsible for the occurrence of posttransplant graft dysfunction and ischaemic-type biliary lesions. While extended criteria donor livers are more vulnerable to IRI, their utilisation is required to address the shortfall in donor organs. Thus, the mitigation of IRI should drive the setting of a new benchmark for marginal organ preservation. Herein, strategies incorporating different modalities of machine perfusion of the liver to alleviate IRI are discussed in conjunction with advantages and disadvantages of individual protocols.Techniques leading to reperfusion of the liver during machine perfusion(in situ normothermic regional perfusion and ex situ normothermic machine perfusion)may mitigate IRI by shortening the ischaemic period of the organs. This benefit potentially escalates from the minimum level, obtained following just partial alleviation of the ischaemic period, to the maximum level, which can be potentially achieved with ischaemia-free organ transplantation. Techniques that do not lead to reperfusion of the liver during machine perfusion(hypothermic,subnormothermic, and controlled-oxygenated rewarming) optimise mitochondrial oxidative function and replenish cellular energy stores, thereby lowering reactive oxygen species production as well as the activation ofdownstream inflammatory pathways during reperfusion. Further mechanistic insights into IRI may guide the development of donor-specific protocols of machine perfusion on the basis of the limitations of individual categories of extended criteria donor organs.

Impact of machine perfusion of the liver on post-transplant biliary complications: A systematic review

AIM To review the clinical impact of machine perfusion(MP) of the liver on biliary complications post-transplantation, particularly ischaemic-type biliary lesions(ITBL). METHODS This systematic review was performed in accordance with the Preferred Reporting Systematic Reviews and MetaAnalysis(PRISMA) protocol. The following databases were searched: PubMed, MEDLINE and Scopus. The keyword "liver transplantation" was used in combination with the free term "machine perfusion". Clinical studies reporting results of transplantation of donor human livers following ex situ or in situ MP were analysed. Details relating to donor characteristics, recipients, technique of MP performed and post-operative biliary complications(ITBL, bile leak and anastomotic strictures) were critically analysed.RESULTS Fifteen articles were considered to fit the criteria for this review. Ex situ normothermic MP was used in 6 studies, ex situ hypothermic MP in 5 studies and the other 4 studies investigated in situ normothermic regional perfusion(NRP) and controlled oxygenated rewarming. MP techniques which have per se the potential to alleviate ischaemia-reperfusion injury: Such as hypothermic MP and NRP, have also reported lower rates of ITBL. Other biliary complications, such as biliary leak and anastomotic biliary strictures, are reported with similar incidences with all MP techniques. There is currently less clinical evidence available to support normothermic MP as a mitigator of biliary complications following liver transplantation. On the other hand, restoration of organ to full metabolism during normothermic MP allows assessment of hepatobiliary function before transplantation, although universally accepted criteria have yet to be validated.CONCLUSION MP of the liver has the potential to have a positive impact on post-transplant biliary complications, specifically ITBL, and expand extended criteria donor livers utilisation.

Current and future perspectives on acute-on-chronic liver failure: Challenges of transplantation, machine perfusion, and beyond

Acute-on-chronic liver failure(ACLF)is a syndrome that occurs in patients with chronic liver disease and is characterized by acute decompensation,organ failure and high short-term mortality.Partially due to the lack of universal diagnostic criteria,the actual ACLF prevalence remains unclear;nevertheless,it is expected to be a highly prevalent condition worldwide.Earlier transplantation is an effective protective measure for selected ACLF patients.Besides liver transplantation,diagnosing and treating precipitant events and providing supportive treatment for organ failures are currently the cornerstone of ACLF therapy.Although new clinical specific therapies have been researched,more studies are necessary to assess safety and efficacy.Therefore,future ACLF management strategies must consider measures to improve access to liver transplantation because the time window for this life-saving therapy is frequently narrow.Thus,an urgent and global discussion about allocation and prioritization for transplantation in critically ill ACLF patients is needed because there is evidence suggesting that the current model may not portray their waitlist mortality.In addition,while donor organ quality is meant to be a prognostic factor in the ACLF setting,recent evidence suggests that machine perfusion of the liver may be a safe tool to improve the donor organ pool and expedite liver transplantation in this scenario.

Machine perfusion of the liver:Putting the puzzle pieces together

The realm of extended criteria liver transplantation created the'adjacent possible'for dynamic organ preservation.Machine perfusion of the liver greatly expanded donor organ preservation possibilities,reaching before unattainable goals,including the mitigation of ischemia-reperfusion injury,viability assessment,and organ reconditioning prior to transplantation.However,current scientific evidence lacks uniformity between studies,perfusion protocols,and acceptance criteria.Construction of collaborative research networks for sharing knowledge should,therefore,enable the development of high-level evidence and guidelines for machine perfusion utilization,including donor acceptance criteria.Finally,this approach shall guarantee conditions for further progress to occur.