Avoiding Ischemia Reperfusion Injury in Liver Transplantation

Summary

Presented here is a protocol to provide a step-by-step ischemia-free liver transplantation protocol under ex situ normothermic machine perfusion (37 °C) of human livers from donors to recipients.

Abstract

Currently, ex situ machine perfusion is a burgeoning technique that provides a better preservation method for donor organs than conventional static cold preservation (0–4 °C). A continuous blood supply to organs using machine perfusion from procurement and preservation to implantation facilitates complete prevention of ischemia reperfusion injury and permits ex situ functional assessment of donor livers before transplantation. In this manuscript, we provide a step-by-step ischemia-free liver transplantation protocol in which an ex situ normothermic machine perfusion apparatus is used for pulsatile perfusion through the hepatic artery and continuous perfusion of the portal vein from human donor livers to recipients. In the perfusion period, biochemical analysis of the perfusate is conducted to assess the metabolic activity of the liver, and a liver biopsy is also performed to evaluate the degree of injury. Ischemia-free liver transplantation is a promising method to avoid ischemia-reperfusion injury and may potentially increase the donor pool for transplantation.

Introduction

Ischemia reperfusion injury (IRI) is a well-known and widespread complication in organ transplantation. Obvious nonimmunological events lead to poor graft outcomes and delayed graft function, which are related to the high proportions of organ failure, re-transplantation, and recipient death¹. Conventional cold storage (CCS) of organs was previously identified as a classic method to slow down metabolism but it does not have an influence on preventing progressive dysfunction and damage to cellular integrity. Furthermore, leukocyte accumulation is induced by reactive oxygen metabolites in the reperfusion phase. All of these biological processes become even more relevant when we use extended criteria donor (ECD) grafts such as fatty livers and those from donors older than 65 years. These ECD grafts are more vulnerable to damage and some other detrimental impacts, especially those from CCS². The technology of normothermic ex situ liver machine perfusion to preserve donor organs has achieved great progress over the past few decades and is entirely feasible in clinical practice³. The safety and viability of warm perfusion techniques in donor organs have been evaluated in preclinical studies, and some study groups have designed new type of perfusate and rewarming tactics in animal models. Some clinical trials of warm perfusion to preserve donor livers have been launched in East Asia, Europe and North America^4,5.

Normothermic machine perfusion (NMP) facilitates a metabolically active scenario in which organs can achieve homeostasis with continuously provisioned oxygen and nutrients. The metabolism of grafts is activated, and we can judge during perfusion whether the donor organs are suitable for transplantation to recipients according to the biochemical index of the perfusate or biopsy of the perfused organs. Available parameters during the preservation period also offer a means for surgeons to treat grafts or restore ECD grafts^6,7.

Red blood cells are the most frequently used oxygen carrier. Some other essential ingredients, including antibiotics, antithrombotic agents, and nutrients are also included in the perfusate⁸. In the current practice, after a liver has been retrieved, it is preserved and back-table prepared in a 0-4︒C solution. Then, the cold liver is perfused in the already prepared NMP apparatus for several hours for assessment and restoration. However, the liver suffers double attacks of IRI at the start of NMP and after implantation, although the liver is protected and repaired to some extent during the NMP process^9,10. Therefore, we attempted to reevaluate the process and reflect on avoidance of the two IRI attacks. We hypothesized that IRI was avoidable if a continuous blood supply was provided to the liver. To verify this hypothesis, we changed the conventional double conversion protocol into an uninterrupted hepatic artery (HA) and portal vein (PV) supply using a Liver-Assist device. This novel transplant procedure was named ischemia-free liver transplantation (IFLT). The first case of IFLT has previously been published and has attracted considerable attention from organ transplantation experts¹¹.

Two rotary pumps providing pulsatile hepatic arterial flow and a continuous PV supply were used in the perfusion device in which the flow was controlled by relevant pressure. The system is controlled by pressure and allows the flow through the liver to be automatically adjusted according to the resistance in the liver. Oxygenation and CO₂ elimination of the perfusate are regulated by two hollow fiber membrane oxygenators. We can set different temperatures according to different types of machine perfusion (ranging from 10 °C to 37 °C). We can monitor and record the real-time pressure, temperature, flow and resistance index in the instrument panel during the perfusion process. Liver assist is not a transportable device. Therefore, the donors used for IFLT should be transferred to the transplant center.

This article aimed to offer a step-by-step IFLT protocol in which an ex situ NMP apparatus is used to provide pulsatile perfusion to the HA and maintain continuous perfusion of the PV from human donor liver procurement to implantation.

Protocol

This protocol was reviewed and approved by the ethics committee of The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China. Informed consent was obtained from all the participants. All the procedures in studies involving human participants were performed in accordance with the 1964 Helsinki Declaration and its later amendments or revisions. 1. Preparation of the perfusion solution and device NOTE: The total volume of the perfusion solution prepared f…

Representative Results

In April 2018, a 66-year-old male donor with brain death was not considered by local transplant centers because of the high risk of graft loss in such donors. The reasons for discarding the liver, at the time of procurement were older age and macroscopic appearance of moderate firmness, round liver edges and suboptimal liver graft perfusion along with major donor comorbidities, which included hypertension, hypertensive heart disease, and the following associated factors: hypernatremia (sodium, 156 mmol/L) and hemodynamic…

Discussion

This IFLT technique was established to completely avoid IRI. This article provides a step-by-step IFLT protocol from organ procurement, ex situ preservation to implantation.

Based on NMP, IFLT provides an uninterrupted supply of blood and oxygen to grafts from procurement and perseveration to implantation. Numerous studies have shown that NMP has significant advantages in reducing IRI, improving organ viability, and repairing graft damage compared to static cold preservation^1…

Materials

10% calcium gluconate	Hebei Tiancheng Pharmaceutical Co, Ltd	1S181124101	30 mL
25% magnesium sulphate	Hebei Tiancheng Pharmaceutical Co, Ltd	H20033861	3 mL
5% sodium bicarbonate	Huiyinbi Group Jiangxi Dongya Pharmaceutical Co, Ltd	H36020283	The amount depends on the pH
Cefoperazone sodium and sulbactam sodium	Pfizer	H20020597	1.5 g
Compound Amino Acid Injection	Guangdong Litai Pharmaceutical Co., Ltd	H20063797	250 mL
Crossed-matched leucocyte-depleted washed red cells	Guangzhou Blood Center	H20033739	1300 mL
Heparin	Chengdu Hepatunn Pharmaceutical Co., Ltd	H51021209	37500 U
Liver Assist	Organ Assist	OA.Li.Li.140	Perfusion device
Liver Assist disposable package	Organ Assist	OA.Li.DP.540	Disposable set and cannulas
Metronidazole	Shanghai Baxter Healthcare Co., Ltd.	H20003301	0.5 g
scalp acupuncture	Wuhan W.E.O.Science & Technology Development Co., Ltd	WEO-JX-32B-5.0 0.7*25mm	Bile duct cannula
Succinylated gelatinor	B. Braun Medical Suzhou Co., Ltd	H20113119	1400 mL