Hyperbaric oxygen therapy for hepatic artery thrombosis following liver transplantation: current concepts

Hyperbaric Oxygen Therapy in Liver Diseases

Hyperbaric oxygen therapy (HBOT) is an efficient therapeutic option to improve progress of lots of diseases especially hypoxia-related injuries, and has been clinically established as a wide-used therapy for patients with carbon monoxide poisoning, decompression sickness, arterial gas embolism, problematic wound, and so on. In the liver, most studies positively evaluated HBOT as a potential therapeutic option for liver transplantation, acute liver injury, nonalcoholic steatohepatitis, fibrosis and cancer, especially for hepatic artery thrombosis. This might mainly attribute to the anti-oxidation and anti-inflammation of HBOT. However, some controversies are existed, possibly due to hyperbaric oxygen toxicity. This review summarizes the current understandings of the role of HBOT in liver diseases and hepatic regeneration. Future understanding of HBOT in clinical trials and its in-depth mechanisms may contribute to the development of this novel adjuvant strategy for clinical therapy of liver diseases.

Small-for-Size Syndrome: Bridging the Gap Between Liver Transplantation and Graft Recovery

In living donor liver transplantation, optimal graft size is estimated from values like graft volume/standard liver volume and graft/recipient body weight ratio but the final functional hepatic mass is influenced by other donor and recipient factors. Grafts with insufficient functional hepatic mass can produce a life-threatening condition with rapidly progressive liver failure called small-for-size syndrome (SFSS). Diagnosis of SFSS requires careful surveillance for signs of inadequate hepatocellular function, residual portal hypertension, and systemic inflammation that suggest rapidly progressive liver failure. Early diagnosis, symptom control, and addressing the cause of SFSS may prevent the need for retransplantation. With increased attention to avoiding donor risk, intensivists will be confronted with more SFSS recipients. In this review, we aim to outline a systematic approach to the medical management of patients with SFSS by providing a concise synopsis of general supportive care—neurological, cardiovascular, and renal support, mechanical ventilation, nutritional support, infection control, and tailored immunosuppression—with an aim to avoid end-organ damage or death and a review of current interventions including liver support devices, portal flow modulating drugs, and other experimental interventions that aim to preserve existing hepatic mass and improve conditions for hepatic regeneration. We examine evidence for SFSS interventions to provide the reader with information that may assist in clinical decision making. Points of controversy in care are purposefully highlighted to identify areas where additional experimental work is still needed. A full understanding of the pathophysiology of SFSS and measures to support liver regeneration will guide effective management.

An innovative hyperbaric hypothermic machine perfusion protects the liver from experimental preservation injury

Purpose. Hypothermic machine perfusion systems seem more effective than the current static storage to prevent cold ischemic liver injury. Thus, we test an innovative hyperbaric hypothermic machine perfusion (HHMP), which combines hyperbaric oxygenation of the preservation solution and continuous perfusion of the graft. Methods. Rat livers were preserved with Celsior solution according to 4 different modalities: normobaric static preservation; hyperbaric static preservation at 2 atmosphere absolute (ATA); normobaric dynamic preservation, with continuous perfusion; hyperbaric dynamic preservation, with continuous perfusion at 2 ATA. After 24 h cold preservation, we assessed different parameters. Results. Compared to baseline, livers preserved with the current static storage showed severe ultrastructural damage, glycogen depletion and an increased oxidative stress. Normobaric perfused livers showed improved hepatocyte ultrastructure and ameliorated glycogen stores, but they still suffered a significant oxidative damage. The addition of hyperbaric oxygen produces an extra benefit by improving oxidative injury and by inducing endothelial NO synthase (eNOS) gene expression. Conclusions. Preservation by means of the present innovative HHMP reduced the liver injury occurring after the current static cold storage by lowering glycogen depletion and oxidative damage. Interestingly, only the use of hyperbaric oxygen was associated to a blunted oxidative stress and an increased eNOS gene expression.

Hyperbaric oxygenation promotes regeneration of biliary cells and improves cholestasis in rats

AIM: To investigate the effects of hyperbaric oxygenation (HBO) on regeneration of the biliary ductal system and postoperative cholestasis in hepatectomized rats.

METHODS: HBO was performed in Wistar rats daily starting 12 h after a 70% partial hepatectomy. Regenerated liver weight, serum parameters and the proliferating cell nuclear antigen labeling index of hepatocytes and biliary ductal cells were measured. Hepatocyte growth factor (HGF), c-Met and transforming growth factor (TGF) β-1 mRNA expression levels were analyzed by quantitative reverse transcription polymerase chain reaction.

RESULTS: HBO improved the postoperative serum levels of total bile acid but not transaminase levels. HBO promoted hepatocyte and biliary ductal cell proliferation. The hematoxylin and eosin-stained specimens revealed fewer ballooned hepatocytes and higher cell densities in the HBO group compared to the control group. HBO suppressed c-Met mRNA levels at 15 h but did not modulate HGF or TGF β-1 mRNA expression levels.

CONCLUSION: HBO promoted regeneration of biliary ductal cells and improved postoperative cholestasis after a partial hepatectomy.

Can hyperbaric oxygenation decrease doxorubicin hepatotoxicity and improve regeneration in the injured liver?

BACKGROUND/PURPOSE

Portal vein embolization is used in the treatment of hepatocellular cancer, with the purpose of enhancing resectability. However, regeneration is restricted due to hepatocellular injury following chemotherapeutics (e.g. doxorubicin). The aim of this study was to investigate whether hyperbaric oxygenation (HBO) can alleviate the hepatotoxicity of chemotherapy and improve regeneration in the injured liver.

METHODS

Rats were allocated to four experimental groups. Group I rats were subjected to right portal vein ligation (RPVL); rats in groups II and III were administered doxorubicin prior to RPVL, with group III rats being additionally exposed to HBO sessions postoperatively; group IV rats was sham-operated. All rats were sacrificed on postoperative day 7, and liver injury was assessed by measuring alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Protein synthetic ability was determined based albumin levels and liver regeneration by the mitotic index (MI).

RESULTS

The AST and ALT values of group II rats were significantly higher than those of group I, but not those of group III. Rats treated with doxorubicin and HBO (groups II and III) showed slightly but not significant differences in albumin levels than those subjected to only RPVL or sham-operated. The MI was significantly increased in groups I, II, and III, with the MI of group III rats significantly higher than those of group I rats.

CONCLUSIONS

Based on our results, we conclude that HBO treatment has the potential to diminish doxorubicin-related hepatotoxicity and improve regeneration in the injured liver.

Current concept of small-for-size grafts in living donor liver transplantation

The extended application of living donor liver transplantation (LDLT) has revealed the problem of graft size mismatching called "small-for-size (SFS) graft syndrome." The initial trials to resolve this problem involved increasing the procured graft size, from left to right, and even extension to include a right lobe graft. Clinical cases of living right lobe donations have been reported since then, drawing attention to the risks of increasing the liver volume procured from a living donor. However, not only other modes of increasing graft volume such as auxiliary or dual liver transplantation, but also control of the increased portal pressure caused by an SFS graft, such as a portosystemic shunt or splenectomy, have been trialed with some positive results. To establish an effective strategy for transplanting SFS grafts and preventing SFS graft syndrome, it is essential to have precise knowledge and tactics to evaluate graft quality and graft volume, when performing these LDLTs with portal pressure control. We reviewed the updated literature on the pathogenesis of and strategies for using SFS grafts.

Strategies for improving the outcomes of small-for-size grafts in adult-to-adult living-donor liver transplantation

Living-donor liver transplantation (LDLT) has been refined and accepted as a valuable treatment for patients with end-stage liver disease in order to overcome the shortage of organs and mortality on the waiting list. However, graft size problems, especially small-for-size (SFS) grafts, remain the greatest limiting factor for the expansion of LDLT, especially in adult-to-adult transplantation. Various attempts have been made to overcome the problems regarding SFS grafts, such as increasing the graft liver volume and/or controlling excessive portal inflow to a small graft, with considerable positive outcomes. Recent innovations in basic studies have also contributed to the treatment of SFS syndrome. Herein, we review the literature and assess our current knowledge of the pathogenesis and treatment strategies for the use of SFS grafts in adult-to-adult LDLT.

Two-year follow-up of splenic radiofrequency ablation in patients with cirrhotic hypersplenism: does increased hepatic arterial flow induce liver regeneration?

BACKGROUND

Hepatocyte hypoxia may be a mechanism determining abnormal tissue oxygenation and dysfunction of the cirrhotic liver. Since the introduction of radiofrequency ablation (RFA) for patients with cirrhotic hypersplenism, we observed a phenomenon of visible hepatic regeneration. This study aims to investigate the potential mechanism of RFA-induced liver regeneration, and the 2-year outcomes of splenic RFA.

METHODS

Forty patients who underwent splenic RFA for cirrhotic hypersplenism were followed for 24 months. Before and after RFA procedures, portal hemodynamics and liver and spleen volumes were measured by Doppler ultrasonography and computed tomography volumetry. Liver function tests and blood counts were also determined.

RESULTS

The splenic and portal venous flows decreased, but hepatic arterial flow (HAF) increased dramatically after the RFA procedure. Liver volumes at 3 month post-RFA increased compared to the baseline volumes (872 +/- 107 vs. 821 +/- 99 cm(3), P = .031). A correlation was found between maximum absolute values of liver volumes (triangle upliver volumes) and that of HAF (triangle upHAF) in Child-Pugh class A/B patients (r = 0.60; P < .001). Leukocyte and platelet counts, as well as liver function, improved substantially during the 2-year follow-up. Patients with > or = 40% of spleen volume ablated had better improvement of thrombocytopenia. No death or severe complications occurred.

CONCLUSIONS

RFA for cirrhotic hypersplenism is safe and efficacious. The increase in HAF as a result of splenic RFA may improve liver function and induce liver regeneration in cirrhotics, but further studies are necessary to clarify the underlying mechanisms.

Microvascular hepatic artery reconstruction in pediatric abdominal transplantation: pearls and pitfalls

The "back-wall first" hepatic artery microanastomosis in pediatric liver transplantation saves lives and reduces morbidity. We describe our technique of hepatic artery reconstruction and offer a systematic and multi-team collaborative approach that optimizes surgical outcomes.