Double-blind placebo-controlled randomized trial of N-acetylcysteine infusion following live donor liver transplantation

The effect of acetylcysteine on the prothrombin time and international normalized ratio: a narrative review

INTRODUCTION

Patients poisoned with paracetamol are treated with acetylcysteine. In patients without hepatocellular injury, an increased prothrombin time or international normalized ratio has been observed during acetylcysteine administration. The international normalized ratio is preferred as it is a standardized calculation of prothrombin time independent of reagents and machinery. Since the prothrombin time and international normalized ratio are used as markers of liver injury in patients with paracetamol poisoning, it is important to assess the magnitude of the effect of acetylcysteine treatment on the prothrombin time and international normalized ratio. The aim of this narrative review is to describe the effect of acetylcysteine on the prothrombin time and international normalized ratio.

METHODS

Embase, PubMed and Web of Science were searched to identify the effect of acetylcysteine on coagulation factors II, VII, IX or X, the prothrombin time and the international normalized ratio in in vitro and in vivo studies in healthy subjects and clinical studies involving both those poisoned with paracetamol and surgical patients. The search terms employed were acetylcysteine combined with prothrombin time, international normalized ratio, coagulation or haemostasis.

RESULTS

The search identified a total of 2,471 articles, of which 19 studies were included. Six in vitro and/or in vivo studies, five clinical studies in paracetamol-poisoned patients and eight clinical studies in surgical patients were included. Acetylcysteine caused a 15-30% increase in prothrombin time and international normalized ratio. This increase was dose-dependent and was caused by a decrease in the activity of coagulation factors II, VII, IX and X. The effect of acetylcysteine on the increased prothrombin time and international normalized ratio was more prominent after the high loading dose but remained present during the lower maintenance dose of acetylcysteine. The effect was observed in both in vitro and in vivo studies and confirmed in clinical studies in paracetamol-poisoned patients without hepatic injury. Studies in surgical patients treated with acetylcysteine showed conflicting results. Twelve of the 13 clinical studies suffered from risk of bias, limiting the value of these studies.

DISCUSSION

The moderate 15-30% increase in the international normalized ratio induced by acetylcysteine is especially important in hospitals using the international normalized ratio as a marker for hepatotoxicity due to paracetamol poisoning and underlines the need for the international normalized ratio to be assessed at admission.

CONCLUSION

Acetylcysteine treatment leads to an estimated 15-30% increase in prothrombin time and international normalized ratio in both experimental studies and paracetamol-poisoned patients. Isolated increases in prothrombin time and international normalized ratio during acetylcysteine infusion are common and do not necessarily reflect liver dysfunction or liver injury.

Risk Factors and Outcomes Associated With the Development of Persistent Acute Kidney Injury in Non-Renal Solid Organ Transplant Recipients: Systematic Review and Meta-Analysis

Persistent acute kidney injury (pAKI), compared with acute kidney injury (AKI) that resolves in <72 h, is associated with worse prognosis in critically ill patients. Definitions and prognosis of pAKI are not well characterized in solid organ transplant patients. Our aims were to investigate (a) definitions and incidence of pAKI; (b) association with clinical outcomes; and (c) risk factors for pAKI among heart, lung, and liver transplant recipients. We systematically reviewed the literature including PubMed, Embase, Web of Science, and Cochrane from inception to 8/1/2023 for human prospective and retrospective studies reporting on the development of pAKI in heart, lung, or liver transplant recipients. We assessed heterogeneity using Cochran's Q and I2. We identified 25 studies including 6330 patients. AKI (8%-71.6%) and pAKI (2.7%-55.1%) varied widely. Definitions of pAKI included 48-72 h (six studies), 7 days (three studies), 14 days (four studies), or more (12 studies). Risk factors included age, body mass index (BMI), diabetes, preoperative chronic kidney disease (CKD), intraoperative vasopressor use, and intraoperative circulatory support. pAKI was associated with new onset of CKD (odds ratio [OR] 1.41-11.2), graft dysfunction (OR 1.81-8.51), and long-term mortality (OR 3.01-13.96), although significant heterogeneity limited certainty of CKD and graft dysfunction outcome analyses. pAKI is common and is associated with worse mortality among liver and lung transplant recipients. Standardization of the nomenclature of AKI will be important in future studies (PROSPERO CRD42022371952).

Viability assessment of the liver during ex-situ machine perfusion prior to transplantation

PURPOSE OF REVIEW

In an attempt to reduce waiting list mortality in liver transplantation, less-than-ideal quality donor livers from extended criteria donors are increasingly accepted. Predicting the outcome of these organs remains a challenge. Machine perfusion provides the unique possibility to assess donor liver viability pretransplantation and predict postreperfusion organ function.

RECENT FINDINGS

Assessing liver viability during hypothermic machine perfusion remains challenging, as the liver is not metabolically active. Nevertheless, the levels of flavin mononucleotide, transaminases, lactate dehydrogenase, glucose and pH in the perfusate have proven to be predictors of liver viability. During normothermic machine perfusion, the liver is metabolically active and in addition to the perfusate levels of pH, transaminases, glucose and lactate, the production of bile is a crucial criterion for hepatocyte viability. Cholangiocyte viability can be determined by analyzing bile composition. The differences between perfusate and bile levels of pH, bicarbonate and glucose are good predictors of freedom from ischemic cholangiopathy.

SUMMARY

Although consensus is lacking regarding precise cut-off values during machine perfusion, there is general consensus on the importance of evaluating both hepatocyte and cholangiocyte compartments. The challenge is to reach consensus for increased organ utilization, while at the same time pushing the boundaries by expanding the possibilities for viability testing.

Bridging the critically ill patient with acute to chronic liver failure to liver transplantation

Liver transplantation (LT) has emerged as an effective therapy for severe forms of acute-on-chronic liver failure (ACLF), an entity characterized by the development of multiorgan failure and high short-term mortality. The aim of critical care management of ACLF patients is to rapidly treat precipitating events and aggressively support failing organs to ensure that patients may successfully undergo LT or, less frequently, recover. Malnutrition and sarcopenia are frequently present, adversely impacting the prognosis of these patients. Management of critical care patients with ACLF is complex and requires the participation of different specialties. Once the patient is stabilized, a rapid evaluation for salvage LT should be performed because the time window for LT is often narrow. The development of sepsis and prolonged organ support may preclude LT or diminish its chances of success. The current review describes strategies to bridge severe ACLF patients to LT, highlights the minimal evaluation required for listing and the currently suggested contraindications to proceed with LT, and addresses different aspects of management during the perioperative and early posttransplant period.

Challenges With the Implementation of Machine Perfusion in Clinical Liver Transplantation

Dynamic organ preservation is a relatively old technique which has regained significant interest in the last decade. Machine perfusion (MP) techniques are applied in various fields of solid organ transplantation today. The first clinical series of ex situ MP in liver transplantation was presented in 2010. Since then, the number of research and clinical applications has substantially increased. Despite the notable beneficial effect on organ quality and recipient outcome, MP is still not routinely used in liver transplantation. Based on the enormous need to better preserve organs and the subsequent demand to continuously innovate and develop perfusion equipment further, this technology is also beneficial to test and deliver future therapeutic strategies to livers before implantation. This article summarizes the various challenges observed during the current shift from static to dynamic liver preservation in the clinical setting. The different organ perfusion strategies are discussed first, together with ongoing clinical trials and future study design. The current status of research and the impact of costs and regulations is highlighted next. Factors contributing to costs and other required resources for a worldwide successful implementation and reimbursement are presented third. The impact of research on cost-utility and effectivity to guide the tailored decision-making regarding the optimal perfusion strategy is discussed next. Finally, this article provides potential solutions to the challenging field of innovation in healthcare considering the various social and economic factors and the role of clinical, regulatory, and financial stakeholders worldwide.

Ferroptosis: a new target for hepatic ischemia-reperfusion injury?

Ischemia-reperfusion injury (IRI) can seriously affect graft survival and prognosis and is an unavoidable event during liver transplantation. Ferroptosis is a novel iron-dependent form of cell death characterized by iron accumulation and overwhelming lipid peroxidation; it differs morphologically, genetically, and biochemically from other well-known cell death types (autophagy, necrosis, and apoptosis). Accumulating evidence has shown that ferroptosis is involved in the pathogenesis of hepatic IRI, and targeting ferroptosis may be a promising therapeutic approach. Here, we review the pathways and phenomena involved in ferroptosis, explore the associations and implications of ferroptosis and hepatic IRI, and discuss possible strategies for modulating ferroptosis to alleviate the hepatic IRI.

Obstacles to implement machine perfusion technology in routine clinical practice of transplantation: Why are we not there yet?

Machine perfusion of solid human organs is an old technique, and the basic principles were presented as early as 1855 by Claude Barnard. More than 50 years ago, the first perfusion system was used in clinical kidney transplantation. Despite the well-known benefits of dynamic organ preservation and significant medical and technical development in the last decades, perfusion devices are still not in routine use. This article describes the various challenges to implement this technology in practice, critically analyzing the role of all involved stakeholders, including clinicians, hospitals, regulatory, and industry, on the background of regional differences worldwide. The clinical need for this technology is discussed first, followed by the current status of research and the impact of costs and regulations. Considering the need for strong collaborations between clinical users, regulatory bodies, and industry, integrated road maps and pathways required to achieve a wider implementation are presented. The role of research development, clear regulatory pathways, and the need for more flexible reimbursement schemes is discussed together with potential solutions to address the most relevant hurdles. This article paints an overall picture of the current liver perfusion landscape and highlights the role of clinical, regulatory, and financial stakeholders worldwide.

Type 2 innate lymphoid cells are protective against hepatic ischaemia/reperfusion injury

BACKGROUND AND AIMS

Although type 2 innate lymphoid cells (ILC2s) were originally found to be liver-resident lymphocytes, the role and importance of ILC2 in liver injury remains poorly understood. In the current study, we sought to determine whether ILC2 is an important regulator of hepatic ischaemia/reperfusion injury (IRI).

METHODS

ILC2-deficient mice (ICOS-T or NSG) and genetically modified ILC2s were used to investigate the role of ILC2s in murine hepatic IRI. Interactions between ILC2s and eosinophils or macrophages were studied in coculture. The role of human ILC2s was assessed in an immunocompromised mouse model of hepatic IRI.

RESULTS

Administration of IL-33 prevented hepatic IRI in association with reduction of neutrophil infiltration and inflammatory mediators in the liver. IL-33-treated mice had elevated numbers of ILC2s, eosinophils, and regulatory T cells. Eosinophils, but not regulatory T cells, were required for IL-33-mediated hepatoprotection in IRI mice. Depletion of ILC2s substantially abolished the protective effect of IL-33 in hepatic IRI, indicating that ILC2s play critical roles in IL-33-mediated liver protection. Adoptive transfer of ex vivo-expanded ILC2s improved liver function and attenuated histologic damage in mice subjected to IRI. Mechanistic studies combining genetic and adoptive transfer approaches identified a protective role of ILC2s through promoting IL-13-dependent induction of anti-inflammatory macrophages and IL-5-dependent elevation of eosinophils in IRI. Furthermore, in vivo expansion of human ILC2s by IL-33 or transfer of ex vivo-expanded human ILC2s ameliorated hepatic IRI in an immunocompromised mouse model of hepatic IRI.

CONCLUSIONS

This study provides insight into the mechanisms of ILC2-mediated liver protection that could serve as therapeutic targets to treat acute liver injury.

IMPACT AND IMPLICATIONS

We report that type 2 innate lymphoid cells (ILC2s) are important regulators in a mouse model of liver ischaemia/reperfusion injury (IRI). Through manipulation of macrophage and eosinophil phenotypes, ILC2s mitigate liver inflammation and injury during liver IRI. We propose that ILC2s have the potential to serve as a therapeutic tool for protecting against acute liver injury and lay the foundation for translation of ILC2 therapy to human liver disease.

N-acetylcysteine in the Donor, Recipient, or Both Donor and Recipient in Liver Transplantation: A Systematic Review With Meta-analysis and Trial Sequential Analysis

BACKGROUND

N-acetylcysteine (NAC) is a potentially effective drug for treating ischemia-reperfusion injury in transplanted livers, but its effect remains controversial.

METHODS

A systematic review and meta-analysis of relevant clinical trials published and registered in the Cochrane Library, MEDLINE, EMBASE, ClinicalTrial.gov , WHO ICTRP, etc, before March 20, 2022 were conducted and registered with PROSPERO (CRD42022315996). Data were pooled using a random effects model or a fixed effects model based on the amount of heterogeneity.

RESULTS

Thirteen studies with 1121 participants, 550 of whom received NAC, were included. Compared with the control, NAC significantly reduced the incidence of primary graft nonfunction (relative risk [RR], 0.27; 95% confidence interval [CI], 0.08-0.96), the incidence of postoperative complications (RR, 0.52; 95% CI, 0.41-0.67), the peak postoperative aspartate transferase level (mean difference [MD], -267.52; 95% CI, -345.35 to -189.68), and the peak alanine transferase level (MD, -293.29; 95% CI, -370.39 to -216.20). NAC also improved 2-y (RR, 1.18; 95% CI, 1.01-1.38) graft survival rate. However, NAC increased the intraoperative cryoprecipitate (MD, 0.94; 95% CI, 0.42-1.46) and red blood cell (MD, 0.67; 95% CI, 0.15-1.19) requirements. Moreover, NAC was administered in various modes in these studies, including to the donor, recipient, or both. Subgroup analysis and network meta-analysis showed that NAC administration to recipients could play a more significant role than the other 2 administration modes.

CONCLUSIONS

Our study supports the protective effect of NAC against LT-induced ischemia-reperfusion injury and shows better clinical outcomes of NAC administration to recipients.

Protective effect of platinum nano-antioxidant and nitric oxide against hepatic ischemia-reperfusion injury

Therapeutic interventions of hepatic ischemia-reperfusion injury to attenuate liver dysfunction or multiple organ failure following liver surgery and transplantation remain limited. Here we present an innovative strategy by integrating a platinum nanoantioxidant and inducible nitric oxide synthase into the zeolitic imidazolate framework-8 based hybrid nanoreactor for effective prevention of ischemia-reperfusion injury. We show that platinum nanoantioxidant can scavenge excessive reactive oxygen species at the injury site and meanwhile generate oxygen for subsequent synthesis of nitric oxide under the catalysis of nitric oxide synthase. We find that such cascade reaction successfully achieves dual protection for the liver through reactive oxygen species clearance and nitric oxide regulation, enabling reduction of oxidative stress, inhibition of macrophage activation and neutrophil recruitment, and ensuring suppression of proinflammatory cytokines. The current work establishes a proof of concept of multifunctional nanotherapeutics against ischemia-reperfusion injury, which may provide a promising intervention solution in clinical use.

Transplant Trial Watch

To keep the transplantation community informed about recently published level 1 evidence in organ transplantation ESOT and the Centre for Evidence in Transplantation (www.transplantevidence.com) have developed the Transplant Trial Watch. The Transplant Trial Watch is a monthly overview of 10 new randomised controlled trials (RCTs) and systematic reviews. This page of Transplant International offers commentaries on methodological issues and clinical implications on 2 articles of particular interest from the CET Transplant Trial Watch monthly selection. For all high quality evidence in solid organ transplantation, visit the Transplant Library (www.transplantlibrary.com).

Viability Assessment in Liver Transplantation-What Is the Impact of Dynamic Organ Preservation?

Based on the continuous increase of donor risk, with a majority of organs classified as marginal, quality assessment and prediction of liver function is of utmost importance. This is also caused by the notoriously lack of effective replacement of a failing liver by a device or intensive care treatment. While various parameters of liver function and injury are well-known from clinical practice, the majority of specific tests require prolonged diagnostic time and are more difficult to assess ex situ. In addition, viability assessment of procured organs needs time, because the development of the full picture of cellular injury and the initiation of repair processes depends on metabolic active tissue and reoxygenation with full blood over several hours or days. Measuring injury during cold storage preservation is therefore unlikely to predict the viability after transplantation. In contrast, dynamic organ preservation strategies offer a great opportunity to assess organs before implantation through analysis of recirculating perfusates, bile and perfused liver tissue. Accordingly, several parameters targeting hepatocyte or cholangiocyte function or metabolism have been recently suggested as potential viability tests before organ transplantation. We summarize here a current status of respective machine perfusion tests, and report their clinical relevance.