Methylene blue in the hepatopulmonary syndrome

Methylene Blue-Based Nano and Microparticles: Fabrication and Applications in Photodynamic Therapy

Methylene blue (MB) has been used in the textile industry since it was first extracted by the German chemist Heinrich Caro. Its pharmacological properties have also been applied toward the treatment of certain diseases such as methemoglobinemia, ifosfamide-induced encephalopathy, and thyroid conditions requiring surgery. Recently, the utilization of MB as a safe photosensitizer in photodynamic therapy (PDT) has received attention. Recent findings demonstrate that photoactivated MB exhibits not only anticancer activity but also antibacterial activity both in vitro and in vivo. However, due to the hydrophilic nature of MB, it is difficult to create MB-embedded nano- or microparticles capable of increasing the clinical efficacy of the PDT. This review aims to summarize fabrication techniques for MB-embedded nano and microparticles and to provide both in vitro and in vivo examples of MB-mediated PDT, thereby offering a future perspective on improving this promising clinical treatment modality. We also address examples of MB-mediated PDT in both cancer and infection treatments. Both in-vitro and in-vivo studies are summarized here to document recent trends in utilizing MB as an effective photosensitizer in PDT. Lastly, we discuss how developing efficient MB-carrying nano- and microparticle platforms would be able to increase the benefits of PDT.

Hepatopulmonary Syndrome and Portopulmonary Hypertension: Pulmonary Vascular Complications of Liver Disease

Pulmonary vascular disease is a frequent complication of chronic liver disease and portal hypertension, affecting up to 30% of patients. There are two distinct pulmonary vascular complications of liver disease: hepatopulmonary syndrome (HPS) and portopulmonary hypertension (POPH). HPS affects 25% of patients with chronic liver disease and is characterized by intrapulmonary vasodilatation and abnormal arterial oxygenation. HPS negatively impacts quality of life and is associated with a 2-fold increased risk of death compared to controls with liver disease without HPS. Angiogenesis, endothelin-1 mediated endothelial dysfunction, monocyte influx, and alveolar type 2 cell dysfunction seem to play important roles in disease pathogenesis but there are currently no effective medical therapies. Fortunately, HPS resolves following liver transplant (LT) with improvements in hypoxemia. POPH is a subtype of pulmonary arterial hypertension (PAH) characterized by an elevated mean pulmonary arterial pressure and pulmonary vascular resistance in the setting of normal left-sided filling pressures. POPH affects 5% to 6% of patients with chronic liver disease. Although the pathogenesis has not been fully elucidated, endothelial dysfunction, inflammation, and estrogen signaling have been identified as key pathways involved in disease pathogenesis. POPH is typically treated with PAH targeted therapy and may also improve with liver transplantation in selected patients. This article highlights what is currently known regarding the diagnosis, management, pathobiology, and outcomes of HPS and POPH. Ongoing research is needed to improve understanding of the pathophysiology and outcomes of these distinct and often misunderstood pulmonary vascular complications of liver disease. © 2021 American Physiological Society. Compr Physiol 11:1-22, 2021.

Pulmonary Complications of Portal Hypertension

The most common pulmonary complications of chronic liver disease are hepatic hydrothorax, hepatopulmonary syndrome, and portopulmonary hypertension. Hepatic hydrothorax is a transudative pleural effusion in a patient with cirrhosis and no evidence of underlying cardiopulmonary disease. Hepatic hydrothorax develops owing to the movement of ascitic fluid into the pleural space. Hepatopulmonary syndrome and portopulmonary hypertension are pathologically linked by the presence of portal hypertension; however, their pathophysiologic mechanisms are significantly different. Hepatopulmonary syndrome is characterized by low pulmonary vascular resistance secondary to intrapulmonary vascular dilatations and hypoxemia; portopulmonary hypertension features elevated pulmonary vascular resistance and constriction/obstruction within the pulmonary vasculature.

Review article: Update on current and emergent data on hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) is a frequent pulmonary complication of end-stage liver disease, characterized by impaired arterial oxygenation induced by intrapulmonary vascular dilatation. Its prevalence ranges from 4% to 47% in patients with cirrhosis due to the different diagnostic criteria applied among different studies. Nitric oxide overproduction and angiogenesis seem to be the hallmarks of a complicated pathogenetic mechanism, leading to intrapulmonary shunting and ventilation-perfusion mismatch. A classification of HPS according to the severity of hypoxemia has been suggested. Contrast-enhanced echocardiography represents the gold standard method for the detection of intrapulmonary vascular dilatations which is required, in combination with an elevated alveolar arterial gradient to set the diagnosis. The only effective treatment which can modify the syndrome’s natural history is liver transplantation. Although it is usually asymptomatic, HPS imparts a high risk of pretransplantation mortality, independently of the severity of liver disease, while there is variable data concerning survival rates after liver transplantation. The potential of myocardial involvement in the setting of HPS has also gained increasing interest in recent research. The aim of this review is to critically approach the existing literature of HPS and emphasize unclear points that remain to be unraveled by future research.

Hepatopulmonary Syndrome and Portopulmonary Hypertension: Implications for Liver Transplantation

Hepatopulmonary syndrome (HPS) and portopulmonary hypertension (PoPH) represent serious pulmonary complications of advanced liver diseases. Orthotopic liver transplantation (OLT) is capable of completely resolving the underlying abnormalities associated with HPS. On the other hand, post-OLT response in patients with PoPH is less predictable, although heavily influenced by pre-OLT mean pulmonary arterial pressure. It remains the case that the opportunity to reverse 2 potentially fatal organ dysfunctions in the liver and the lung make HPS and PoPH more than worthy for further clinical investigations.

Prolonged Unexplained Hypoxemia as Initial Presentation of Cirrhosis: A Case Report

Patient: Male, 43

Final Diagnosis: Hepatopulmonary syndrome

Symptoms: Dyspnea

Medication: —

Clinical Procedure: —

Specialty: Gastroenterology and Hepatology

Use of Methylene Blue to Treat Hypovolemic Shock Followed by Ischemia-Reperfusion Injury in the Postoperative Orthotopic Liver Transplant Patient: A Case Report

A 57-year-old female patient received elective liver transplant due to nonalcoholic steatohepatitis complicated by hepatocellular carcinoma. Her preoperative Model for End-Stage Liver Disease score was 11. The total transplant ischemic time was 10 hours and 35 minutes, and the warm ischemic time was 35 minutes. Even with aggressive fluid overload and use of high concentrations of vasoactive amines, the patient developed possible primary graft dysfunction with poor response to fluids and vasopressor support, suggesting vasoplegic syndrome. On the basis of the hypothesis of vasoplegic syndrome, the patient received methylene blue intravenously (100 mg bolus for 12 h/1.5 mg/kg). The catastrophic situation was controlled. The patient's urine output markedly improved, she was subsequently weaned from vasoactive support, and mechanical ventilation was discontinued 2 days later. The patient was discharged on the 20th postoperative day.

Hepatopulmonary syndrome: What we know and what we would like to know

Hepatopulmonary syndrome (HPS) is characterized by abnormalities in blood oxygenation caused by the presence of intrapulmonary vascular dilations (IPVD) in the context of liver disease, generally at a cirrhotic stage. Knowledge about the subject is still only partial. The majority of the information about the etiopathogenesis of HPS has been obtained through experiments on animals. Reported prevalence in patients who are candidates for a liver transplantation (LT) varies between 4% and 32%, with a predominance of mild or moderate cases. Although it is generally asymptomatic it does have an impact on their quality of life and survival. The diagnosis requires taking an arterial blood gas sample of a seated patient with alveolar-arterial oxygen gradient (AaO₂) ≥ 15 mm Hg, or ≥ 20 mm Hg in those over 64 years of age. The IPVD are identified through a transthoracic contrast echocardiography or a macroaggregated albumin lung perfusion scan (^99mTc-MAA). There is currently no effective medical treatment. LT has been shown to reverse the syndrome and improve survival rates, even in severe cases. Therefore the policy of prioritizing LT would appear to increase survival rates. This paper takes a critical and clinical look at the current understanding of HPS, as well as the controversies surrounding it and possible future research.

Inflammatory bowel diseases, chronic liver diseases and the lung

This review is devoted to the distinct associations of inflammatory bowel diseases (IBD) and chronic liver disorders with chronic airway diseases, namely chronic obstructive pulmonary disease and bronchial asthma, and other chronic respiratory disorders in the adult population. While there is strong evidence for the association of chronic airway diseases with IBD, the data are much weaker for the interplay between lung and liver multimorbidities. The association of IBD, encompassing Crohn's disease and ulcerative colitis, with pulmonary disorders is underlined by their heterogeneous respiratory manifestations and impact on chronic airway diseases. The potential relationship between the two most prevalent liver-induced pulmonary vascular entities, i.e. portopulmonary hypertension and hepatopulmonary syndrome, and also between liver disease and other chronic respiratory diseases is also approached. Abnormal lung function tests in liver diseases are described and the role of increased serum bilirubin levels on chronic respiratory problems are considered.

Hepatopulmonary Syndrome

Hepatopulmonary syndrome (HPS) is a pulmonary complication observed in patients with chronic liver disease and/or portal hypertension, attributable to an intrapulmonary vascular dilatation that may induce severe hypoxemia. Microvascular dilation and angiogenesis in the lung have been identified as pathologic features that drive gas exchange abnormalities in experimental HPS. Pulse oximetry is a useful screening test for HPS, which can guide subsequent use of arterial blood gases. Contrast-enhanced echocardiography, perfusion lung scanning, and pulmonary arteriography are three currently used diagnostic imaging modalities that identify the presence of intrapulmonary vascular abnormalities. The presence of HPS increases mortality and impairs quality of life, but is reversible with liver transplantation. No medical therapy is established as effective for HPS. At the present time, liver transplantation is the only available treatment for HPS.

Hepatopulmonary syndrome and portopulmonary hypertension: recent knowledge in pathogenesis and overview of clinical assessment

Hepatopulmonary syndrome and portopulmonary hypertension are cardiopulmonary complications, which are not infrequently seen in patients with liver disease and/or portal hypertension. These entities are both clinically and pathophysiologically different: the hepatopulmonary syndrome is characterized by abnormal pulmonary vasodilation and right-to-left shunting resulting in gas exchange abnormalities, whereas portopulmonary hypertension is caused by pulmonary artery vasoconstriction leading to hemodynamic failure. As both hepatopulmonary syndrome and portopulmonary hypertension are associated with significantly increased morbidity and mortality, and as these patients are commonly asymptomatic, all liver transplantation candidates should be actively screened for the presence of these two complications. The aim of is this review is to provide an overview on the hepatopulmonary syndrome and portopulmonary hypertension with primary focus on diagnosis and recent knowledge regarding pathogenesis and therapeutic targets.

Proposed management algorithm for severe hypoxemia after liver transplantation in the hepatopulmonary syndrome

The hepatopulmonary syndrome (HPS) is defined as the triad of liver disease, intrapulmonary vascular dilatation, and abnormal gas exchange, and is found in 10-32% of patients with liver disease. Liver transplantation is the only known cure for HPS, but patients can develop severe posttransplant hypoxemia, defined as a need for 100% inspired oxygen to maintain a saturation of ≥85%. This complication is seen in 6-21% of patients and carries a 45% mortality. Its management requires the application of specific strategies targeting the underlying physiologic abnormalities in HPS, but awareness of these strategies and knowledge on their optimal use is limited. We reviewed existing literature to identify strategies that can be used for this complication, and developed a clinical management algorithm based on best evidence and expert opinion. Evidence was limited to case reports and case series, and we determined which treatments to include in the algorithm and their recommended sequence based on their relative likelihood of success, invasiveness, and risk. Recommended therapies include: Trendelenburg positioning, inhaled epoprostenol or nitric oxide, methylene blue, embolization of abnormal pulmonary vessels, and extracorporeal life support. Availability and use of this pragmatic algorithm may improve management of this complication, and will benefit from prospective validation.

Hepatopulmonary syndrome: the anaesthetic considerations

Hepatopulmonary syndrome (HPS) is a pulmonary complication observed in patients with chronic liver disease and/or portal hypertension, attributable to an intrapulmonary vascular dilatation that induces severe hypoxaemia. Considering the favourable long-term survival of HPS patients as well as the reversal of the syndrome with a functional liver graft, HPS is now an indication for orthotopic liver transplantation (OLT). Consequently, blood gas analysis and imaging techniques should be performed when cirrhotic patients present with shortness of breath as well as when OLT candidates are placed on the transplant waiting list. If the arterial partial pressure of oxygen (PaO2) is more than 10.7 kPa when breathing room air, HPS can be excluded and no other investigation is needed. When the PaO2 when breathing room air is 10.7 kPa or less, contrast-enhanced echocardiography should be performed to exclude pulmonary vascular dilatation. Lung function tests may also help detect additional pulmonary diseases that can contribute to impaired oxygenation. When contrast-enhanced echocardiography is negative, HPS is excluded and no follow-up is needed. When contrast-enhanced echocardiography is positive and PaO2 less than 8 kPa, patients should obtain a severity score that provides them with a reasonable probability of being transplanted within 3 months. In mild-to-moderate HPS (PaO2 8 to 10.6 kPa), periodic follow-up is recommended every 3 months to detect any further deterioration in PaO2. Although no intraoperative deaths have been directly attributed to HPS, oxygenation may worsen immediately following OLT due to volume overload and postoperative infections. Mechanical ventilation is often prolonged with an extended stay in the ICU. A high postoperative mortality (mostly within 6 months) is observed in this group of patients in comparison to non-HPS patients. However, the recovery of an adequate PaO2 within 12 months after OLT explains the similar outcome of HPS and non-HPS patients following OLT over a longer time period.

Hepatopulmonary syndrome

The hepatopulmonary syndrome (HPS) is a pulmonary complication of cirrhosis and/or portal hypertension whereby patients develop hypoxemia as a result of alterations in pulmonary microvascular tone and architecture. HPS occurs in up to 30% of patients with cirrhosis. Although the degree of hypoxemia does not reliably correlate with the severity of liver disease, patients with HPS have a higher mortality than do patients with cirrhosis without the disorder. There has been progress into defining the mechanisms that lead to hypoxemia in HPS, but to date there are no therapeutic options for HPS aside from liver transplantation.

The role of receptor tyrosine kinase activation in cholangiocytes and pulmonary vascular endothelium in experimental hepatopulmonary syndrome

Pulmonary vascular dilation and angiogenesis underlie experimental hepatopulmonary syndrome (HPS) induced by common bile duct ligation (CBDL) and may respond to receptor tyrosine kinase (RTK) inhibition. Vascular endothelial growth factor-A (VEGF-A) expression occurs in proliferating cholangiocytes and pulmonary intravascular monocytes after CBDL, the latter contributing to angiogenesis. CBDL cholangiocytes also produce endothelin-1 (ET-1), which triggers lung vascular endothelin B receptor-mediated endothelial nitric oxide synthase (eNOS) activation and pulmonary intravascular monocyte accumulation. However, whether RTK pathway activation directly regulates cholangiocyte and pulmonary microvascular alterations in experimental HPS is not defined. We assessed RTK pathway activation in cholangiocytes and lung after CBDL and the effects of the type II RTK inhibitor sorafenib in experimental HPS. Cholangiocyte VEGF-A expression and ERK activation accompanied proliferation and increased hepatic and circulating ET-1 levels after CBDL. Sorafenib decreased each of these events and led to a reduction in lung eNOS activation and intravascular monocyte accumulation. Lung monocyte VEGF-A expression and microvascular Akt and ERK activation were also found in vivo after CBDL, and VEGF-A activated Akt and ERK and angiogenesis in rat pulmonary microvascular endothelial cells in vitro. Sorafenib inhibited VEGF-A-mediated signaling and angiogenesis in vivo and in vitro and improved arterial gas exchange and intrapulmonary shunting. RTK activation in experimental HPS upregulates cholangiocyte proliferation and ET-1 production, leading to pulmonary microvascular eNOS activation, intravascular monocyte accumulation, and VEGF-A-mediated angiogenic signaling pathways. These findings identify a novel mechanism in cholangiocytes through which RTK inhibition ameliorates experimental HPS.

Pharmacological treatment for hepatopulmonary syndrome

AIM

Hepatopulmonary syndrome is a pulmonary dysfunction in the context of liver cirrhosis characterized by arterial deoxygenation. Affected patients have increased morbidity and mortality, and many of them expire before undergoing liver transplantation. Therefore, finding medical therapy as a bridge to transplantation or as a final treatment is necessary. In this study, we aimed to review the current literature about pharmacological options available for treatment of hepatopulmonary syndrome.

METHODS

A PubMED and Scopus search was conducted in January 2013 on the English literature published in any time period to find human and animal studies reporting pharmacological therapy of hepatopulmonary syndrome.

RESULTS

Out of 451 studies, 29 relevant articles were included. The number of patients, type, dose, duration, and mechanism of drugs in these studies was extracted and summarized separately. Most of pharmacologic agents act through inhibition of nitric oxide synthase and reduction in nitric oxide production, inactivation of endothelin-1, and treatment of bacterial translocation and pulmonary angiogenesis.

CONCLUSION

Several drugs have been applied for the treatment of HPS with conflicting results. However, no large randomized trial has been conducted probably due to low number of patients. Multicentered clinical trials are necessary to investigate these drugs.

Hepatopulmonary syndrome: update on pathogenesis and clinical features

Hepatopulmonary syndrome (HPS) is a serious vascular complication of liver disease that occurs in 5-32% of patients with cirrhosis. The presence of HPS markedly increases mortality. No effective medical therapies are currently available and liver transplantation is the only established treatment option for HPS. The definition and diagnosis of HPS are established by the presence of a triad of liver disease with intrapulmonary vascular dilation that causes abnormal arterial gas exchange. Experimental biliary cirrhosis induced by common bile duct ligation in the rat reproduces the pulmonary vascular and gas exchange abnormalities of human HPS and serves as a pertinent animal model. Pulmonary microvascular dilation and angiogenesis are two central pathogenic features that drive abnormal pulmonary gas exchange in experimental HPS, and thus might underlie HPS in humans. Defining the mechanisms involved in the microvascular alterations of HPS has the potential to lead to effective medical therapies. This Review focuses on the current understanding of the pathogenesis, clinical features and management of HPS.

Exhaled nitric oxide (FENO) in non-pulmonary diseases

Exhaled nitric oxide (F(E)NO) represents the only exhaled biomarker that has reached clinical practice even in primary care settings, due to the non-invasiveness of its assessment and ease of repeat measurements, even in patients with severe airflow obstruction. While F(E)NO has been suggested as a readily determined biomarker that can aid in the diagnosis and management of asthma, its potential role in pathophysiology of non-pulmonary diseases is less clear and therefore remains to be established. The purpose of the present review is to highlight the current literature investigating the use of F(E)NO in the diagnosis and management of non-pulmonary diseases.

Medical management of chronic liver diseases (CLD) in children (part II): focus on the complications of CLD, and CLD that require special considerations

Treatment of the causes of many chronic liver diseases (CLDs) may not be possible. In this case, complications must be anticipated, prevented or at least controlled by the best available therapeutic modalities. There are three main goals for the management of portal hypertension: (i) prevention of the first episode of variceal bleeding largely by non-selective β-adrenoceptor antagonists, which is not generally recommended in children; (ii) control of bleeding by using a stepwise approach from the least to most invasive strategies; (iii) and prevention of re-bleeding using bypass operations, with particular enthusiasm for the use of meso-Rex bypass in the pediatric population. Hepatic encephalopathy management also consists of three main aspects: (i) ruling out other causes of encephalopathy; (ii) identifying and treating precipitating factors; and (iii) starting empiric treatment with drugs such as lactulose, rifaximin, sodium benzoate, and flumazenil. Treatment of mild ascites and peripheral edema should begin with the restriction of sodium and water, followed by careful diuresis, then large-volume paracentesis associated with colloid volume expansion in severe cases. Empiric broad spectrum antimicrobial therapy should be used for the treatment of spontaneous bacterial peritonitis, bacterial and fungal sepsis, and cholangitis, after taking appropriate cultures, with appropriate changes in therapy after sensitivity testing. Empirical therapies continue to be the standard practice for pruritus; these consist of bile acid binding agents, phenobarbital (phenobarbitone), ursodeoxycholic acid, antihistamines, rifampin (rifampicin), and carbamazepine. Partial external biliary diversion can be used in refractory cases. Once hepatorenal syndrome is suspected, treatment should be initiated early in order to prevent the progression of renal failure; approaches consist of general supportive measures, management of concomitant complications, screening for sepsis, treatment with antibiotics, use of vasopressin analogs (terlipressin), and renal replacement therapy if needed. Hepatopulmonary syndrome and portopulmonary hypertension are best managed by liver transplantation. Provision of an adequate caloric supply, nutrition, and vitamin/mineral supplements for the management of growth failure, required vaccinations, and special care for ensuring psychologic well-being should be ensured. Anticoagulation might be attempted in acute portal vein thrombosis. Some CLDs, such as extrahepatic biliary atresia (EHBA), Crigler-Najjar syndrome, and Indian childhood cirrhosis, require special considerations. For EHBA, Kasai hepatoportoenterostomy is the current standard surgical approach in combination with nutritional therapy and supplemental fat and water soluble vitamins, minerals, and trace elements. In type 1 Crigler-Najjar syndrome, extensive phototherapy is the mainstay of treatment, in association with adjuvant therapy to bind photobilirubin such as calcium phosphate, cholestyramine, or agar, until liver transplantation can be carried out. Treating Indian childhood cirrhosis with penicillamine early in the course of the disease and at doses similar to those used to treat Wilson disease decreases the mortality rate by half. New hopes for the future include extracorporeal liver support devices (the molecular adsorbent recirculating system [MARS®] and Prometheus®), hepatocyte transplantation, liver-directed gene therapy, genetically engineered enzymes, and therapeutic modalities targeting fibrogenesis. Hepapoietin, a naturally occurring cytokine that promotes hepatocyte growth, is under extensive research.

Cardiovascular changes in cirrhosis: pathogenesis and clinical implications

Liver cirrhosis is associated with a wide range of cardiovascular abnormalities including hyperdynamic circulation, cirrhotic cardiomyopathy, and pulmonary vascular abnormalities. The pathogenic mechanisms of these cardiovascular changes are multifactorial and include neurohumoral and vascular dysregulations. Accumulating evidence suggests that cirrhosis-related cardiovascular abnormalities play a major role in the pathogenesis of multiple life-threatening complications including hepatorenal syndrome, ascites, spontaneous bacterial peritonitis, gastroesophageal varices, and hepatopulmonary syndrome. Treatment targeting the circulatory dysfunction in these patients may improve the short-term prognosis while awaiting liver transplantation. Careful fluid management in the immediate post-transplant period is extremely important to avoid cardiac-related complications. Liver transplantation results in correction of portal hypertension and reversal of all the pathophysiological mechanisms that lead to the cardiovascular abnormalities, resulting in restoration of a normal circulation. The following is a review of the pathogenesis and clinical implications of the cardiovascular changes in cirrhosis.

Effect of chronic methylene blue administration on hypoxemia in rats with common bile duct ligation

AIM

Acute administration of methylene blue (MB) can reverse hypoxemia in patients with hepatopulmonary syndrome (HPS). We evaluated the effect of chronic MB administration in common bile duct-ligated rats, which develop HPS by 5 weeks after surgery.

METHODS

A total of 96 Sprague-Dawley rats were used, including 63 rats with common bile duct ligation (CBDL), 22 sham-operated rats and 11 normal control rats. MB (6 mg/kg) was injected s.c. once a day for 4 weeks. Evaluation of hemodynamics and intrapulmonary vascular dilatation (IPVD), as well as blood sampling for arterial blood gas analysis, were done under conscious and unrestrained conditions. Hemodynamics were assessed by the reference sample method using (141)Ce-microspheres (15 microm in diameter), and IPVD was also determined by i.v. injection of these microspheres. Histological examination of the lungs was done with hematoxylin-eosin staining and immunohistochemical staining for von Willebrand factor or vascular endothelial growth factor.

RESULTS

Both the arterial oxygen tension and alveolar-arterial oxygen difference were significantly improved in MB-treated CBDL rats. The hyperdynamic circulation and splanchnic hyperemia seen in untreated CBDL rats were also alleviated by MB treatment. However, IPVD was not affected by MB. Histological examination of the lungs indicated that MB treatment reduced the proliferation of alveolar capillary vessels and angiogenesis, leading to improvement of arterial dysoxygenation. Hepatic synthetic and detoxification functions, as well as renal function, were not altered by MB treatment.

CONCLUSION

Methylene blue may be a candidate treatment for HPS that does not cause deterioration of hepatic or renal function.

Pulmonary manifestations of liver diseases

Respiratory problems are common in patients with chronic liver diseases. The most common causes are disorders that are not related to liver diseases such as asthma and COPD. In addition certain liver diseases that are associated with specific pulmonary abnormalities, and conditions associated with end stage liver disease like tense ascites and intercostal muscular wasting are considered. Finally two unique disorders characterizing by vascular abnormalities independent of cardiorespiratory disorder-the hepatopulmonary syndrome (HPS) and portopulmonary hypertension (POPH) are observed. These disorders have different pathogenesis, different clinical pictures, treatment and prognosis. This article reviews the epidemiology, pathophysiology, clinical features, evaluation and current therapy of these two disorders.

Intestinal endotoxemia plays a central role in development of hepatopulmonary syndrome in a cirrhotic rat model induced by multiple pathogenic factors

AIM: To characterize the correlation between severity of hepatopulmonary syndrome (HPS) and degree of hepatic dysfunction, and to explore how intestinal endotoxemia (IETM) affects the development of HPS in cirrhotic rats.

METHODS: Male Wister rats were fed with a diet containing maize flour, lard, cholesterol, and alcohol and injected subcutaneously with CCl₄ oil solution every two days for 8 wk to induce typical cirrhosis and development of HPS. The animals were also given a nitric oxide (NO) production inhibitor, N^ω-nitro-L-arginine methyl ester (L-NAME) intraperitoneally, and an iNOS inhibitor, aminoguanidine hydrochloride (AG) via gavage daily from the end of the 4th wk to the end of the 6th or 8th wk, or a HO-1 inhibitor, zinc protoporphyrin (ZnPP) intraperitoneally 12 h prior to killing. Blood, liver and lung tissues were sampled.

RESULTS: Histological deterioration of the lung paralleled to that of the liver in the cirrhotic rats. The number of pulmonary capillaries was progressively increased from 6.1 ± 1.1 (count/filed) at the 4th wk to 14.5 ± 2.4 (count/filed) at the 8th wk in the cirrhotic rats. Increased pulmonary capillaries were associated with increased blood levels of lipopolysaccharide (LPS) (0.31 ± 0.08 EU/mL vs control 0.09 ± 0.03 EU/mL), alanine transferase (ALT, 219.1 ± 17.4 U/L vs control 5.9 ± 2.2 U/L) and portal vein pressure. Compared with normal control animals, the number of total cells in bronchoalveolar lavage fluid (BALF) of the cirrhotic rats at the 8th wk was not changed, but the number of macrophages and the ratio of macrophages to total cells were increased by nearly 2-fold, protein expression of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) started to increase significantly at the 4th wk, and reached its peak at the 8th wk in the lung of cirrhotic rats. The increase of iNOS expression appeared to be quicker than that of eNOS. NO₂^-/NO₃^- was also increased, which was correlated to the increase of iNOS (r = 0.7699, P < 0.0001) and eNOS (r = 0.5829, P < 0.002). mRNA expression of eNOS and iNOS was highly consistent with their protein expression.

CONCLUSION: Progression and severity of HPS as indicated by both increased pulmonary capillaries and histological changes are closely associated with LPS levels and progression of hepatic dysfunction as indicated by increased levels of ALT and portal vein pressure. Intestinal endotoxemia plays a central role in the development of HPS in the cirrhotic rat model by inducing NO and/or CO.

Therapy Insight: hepatopulmonary syndrome and orthotopic liver transplantation

Hepatopulmonary syndrome (HPS)--a pulmonary complication observed in patients who have chronic liver disease and/or portal hypertension--is attributed to intrapulmonary vascular dilatation and induces severe hypoxemia. HPS is mainly detected when patients are included on the waiting list for orthotopic liver transplantation (OLT) and can be diagnosed by blood gas analysis, transthoracic contrast-enhanced echocardiography or body scan with (99m)Tc-labeled macroaggregated albumin perfusion. When the partial pressure of arterial oxygen (PaO(2)) is >or=80 mmHg, it is unlikely that the patient has HPS. When the PaO(2) is <80 mmHg, imaging techniques should be used to confirm or exclude pulmonary vascular dilatation. When a diagnosis of HPS is confirmed, knowing the degree of hypoxemia is crucial for optimum patient management. Patients who have a PaO(2) >or=50 mmHg but <60 mmHg should be prioritized for OLT. This procedure is not indicated for patients with a PaO(2) between 60 mmHg and 80 mmHg, although follow-up every 3 months is recommended to detect any deterioration of the PaO(2). A PaO(2) of <50 mmHg might preclude OLT, because mortality and morbidity after OLT are greatly increased in these patients.

Deleterious effect of nitric oxide inhibition in chronic hepatopulmonary syndrome

On the basis of limited experimental and clinical studies, increased activity of the vasodilatory nitric oxide-cyclic guanosine monophosphate pathway is considered to play a key role in the pathogenesis of hepatopulmonary syndrome. We report a 46-year-old woman with Child-Pugh class C cirrhosis and progressive dyspnoea for 12 months. Investigations revealed elevated circulating concentrations of nitric oxide metabolites and exhaled nitric oxide levels, an hyperdynamic circulation with low systemic vascular resistance and mean arterial pressure, a large right to left intrapulmonary shunt fraction on radiolabelled macroaggregated albumin perfusion scanning, positive contrast-enhanced echocardiography, reduced diffusion capacity of carbon monoxide, hypoxaemia and orthodeoxyia, all in keeping with severe hepatopulmonary syndrome. Sequential inhibition of the nitric oxide-cyclic guanosine monophosphate pathway using curcumin (diferuloylmethane), terlipressin and methylene blue was associated with substantial improvements in vascular tone and the hyperdynamic circulation. No improvement, however, in the intrapulmonary shunt was demonstrated. Both hypoxaemia and orthodeoxia were substantially, reproducibly and reversibly worsened with all three treatments. Our findings argue against the contention that intrapulmonary shunting and impairment in arterial oxygenation in hepatopulmonary syndrome are necessarily the consequence of on-going, nitric oxide-cyclic guanosine monophosphate-mediated vasodilatation, at least in the chronic stage, and, given the possibility of substantial worsening of pulmonary oxygen exchange, suggest that inhibition of the nitric oxide-cyclic guanosine monophosphate pathway should be avoided in this setting.

Hepatopulmonary syndrome in patients with hypoxic hepatitis

BACKGROUND & AIMS

The hepatopulmonary syndrome (HPS) is defined as the triad of liver disease, arterial deoxygenation, and widespread pulmonary vasodilatation. Hypoxic hepatitis, also known as ischemic hepatitis, is the leading cause of acute liver impairment in hospitals. It is unknown whether HPS occurs in hypoxic hepatitis. We assessed the prevalence and clinical consequences of HPS in patients with hypoxic hepatitis.

METHODS

Forty-four patients with hypoxic hepatitis were screened prospectively for HPS using established criteria: (1) presence of hepatic disease, (2) increased alveolar-arterial difference for the partial pressure of oxygen greater than the age-related threshold, and (3) intrapulmonary vasodilatation detected via contrast-enhanced echocardiography. Sixty-two critically ill patients with different cardiopulmonary diseases but without hepatic disease were screened for prevalence of intrapulmonary vasodilatation as a control group.

RESULTS

Criteria of HPS were fulfilled in 18 patients with hypoxic hepatitis. HPS-positive patients had a significantly decreased partial pressure of arterial oxygen (P = .001) and partial pressure of arterial oxygen/fraction of inspired oxygen ratio (P = .034) at the time of diagnosis of HPS, a significant decreased area under the curve of the partial pressure of arterial oxygen/fraction of inspired oxygen ratio during the first 48 hours after diagnosis of hypoxic hepatitis (P = .009), and a significantly increased peak serum aspartate transaminase level (P = .028), compared with patients without HPS. Complete resolution of intrapulmonary vasodilatation was observed during follow-up evaluation. Contrast-enhanced echocardiography was negative for intrapulmonary vasodilatation in all 62 control patients.

CONCLUSIONS

Intrapulmonary vasodilatation indicating HPS frequently occurs in patients with hypoxic hepatitis. It is reversible after normalization of the hepatic dysfunction. Clinicians should consider intrapulmonary vasodilatation and HPS in patients with hypoxic hepatitis.

Effects of nebulized N(G)-nitro-L-arginine methyl ester in patients with hepatopulmonary syndrome

Enhanced pulmonary production of nitric oxide (NO) has been implicated in the pathogenesis of hepatopulmonary syndrome (HPS). NO inhibition with N(G)-nitro-L-arginine methyl ester (L-NAME) in both animals and humans with HPS has improved arterial hypoxemia. We assessed the role of enhanced NO production in the pathobiology of arterial deoxygenation in HPS and the potential therapeutic efficacy of selective pulmonary NO inhibition. We investigated the effects of nebulized L-NAME (162.0 mg) at 30 and 120 minutes on all intrapulmonary and extrapulmonary factors governing pulmonary gas exchange in 10 patients with HPS (60 +/- 7 [SD] yr; alveolar-arterial oxygen gradient, range 19-76 mm Hg; arterial oxygen tension, range 37-89 mm Hg). Nebulized L-NAME maximally decreased exhaled NO (by -55%; P < .001), mixed venous nitrite/nitrate (by -12%; P = .02), and cardiac output (by -11%; P = .002) while increased systemic vascular resistance (by 11%; P = .008) and pulmonary vascular resistance (by 25%; P = .03). In contrast, ventilation-perfusion mismatching, intrapulmonary shunt and, in turn, arterial deoxygenation remained unchanged. In conclusion, gas exchange disturbances in HPS may be related to pulmonary vascular remodeling rather than to an ongoing vasodilator effect of enhanced NO production.

Hepatopulmonary syndrome

The hepatopulmonary syndrome is an increasingly important vascular complication of cirrhosis where microvascular dilatation impairs arterial oxygenation in the setting of liver disease. This syndrome is identified in as many as 20% of patients evaluated for liver transplantation and results in increased mortality. No clearly effective medical therapies are available, and liver transplantation is the only established treatment. Pathophysiologic insights obtained from experimental models may lead to the development of novel and effective medical treatments.

Effects of nitric oxide inhibition by methylene blue in cirrhotic patients with ascites

Increased endogenous nitric oxide production has been proposed as an important mediator of the peripheral arterial vasodilation and the hyperdynamic circulation in cirrhosis, whereas a decreased intrahepatic production of nitric oxide has been implicated in the pathogenesis of portal hypertension. The present study investigated the possible beneficial effects of methylene blue, which is a potent inhibitor of guanylate cyclase and nitric oxide synthase, on hyperdynamic circulation and renal function in cirrhotic patients with ascites together with the effects on portal hemodynamics. Twenty patients were evaluated at baseline and during 2 consecutive 4-hr periods after the administration of methylene blue at a dose of 3 mg/kg (10 patients) or placebo (10 patients). Mean arterial pressure, heart rate, cardiac output, systemic vascular resistance, plasma active renin, plasma aldosterone, plasma antidiuretic hormone, serum urea, serum creatinine, serum sodium, urinary flow rate, glomerular filtration rate, effective renal plasma flow, portal flow volume, and portal vein velocity were not modified by methylene blue or placebo. Urinary sodium excretion, fractional sodium excretion and serum nitric oxide levels were significantly decreased 4 hr after methylene blue administration (P < 0.05), to return toward basal levels over a further 4-hr period. It is concluded that methylene blue, at the dose used in the present study, has no effect on systemic and portal hemodynamics in cirrhotic patients with ascites. The reduction in renal sodium excretion, in the absence of changes in renal function and hemodynamics, suggests, at least partly, a direct antinatriuretic effect of methylene blue.

Carboxyhemoglobin levels in cirrhotic patients with and without hepatopulmonary syndrome

BACKGROUND AND AIMS

Heme oxygenase (HO) catalyzes hemoglobin into bilirubin, iron, and carbon monoxide (CO), a known vasodilator. HO expression and CO production as measured by blood carboxyhemoglobin (COHb) levels increase in experimental hepatopulmonary syndrome (HPS) and contribute to vasodilatation. Whether CO contributes to HPS in humans is unknown. Our aim was to assess if arterial COHb levels are increased in cirrhotic patients with HPS relative to those without HPS.

METHODS

We collected data prospectively in stable nonsmoking outpatients with cirrhosis. Demographic and clinical data and room-air arterial blood gases were collected and analyzed. HPS was diagnosed using established criteria.

RESULTS

A total of 159 patients were studied. HPS was present in 27 (17%) patients. Mean age was 52 +/- 9 years, 54% were men, and hepatitis C and/or alcohol were the most common causes (53%). Fourteen percent were Child-Pugh class A, 53% were Child-Pugh class B, and 33% were Child-Pugh class C. Demographic and clinical features were similar between HPS and non-HPS patients except for the Child-Pugh score, which was lower in patients with HPS. Arterial Pa o 2 levels were lower and the alveolar-arterial oxygen gradient was higher in patients with HPS ( P < .001). COHb levels were increased in HPS relative to non-HPS ( P < .001) and correlated with Pa o 2 ( P < .001) and Aa po 2 ( P < .001) levels.

CONCLUSIONS

COHb levels are increased in cirrhotic patients with HPS and correlate with gas exchange abnormalities. These results are consistent with findings in experimental HPS and suggest that CO may contribute to human HPS.

The Incidence of self-prescribed oral complementary and alternative medicine use by patients with gastrointestinal diseases

GOALS

To assess the incidence of oral complementary and alternative medicine (CAM) usage by gastroenterology patients at a single university center and compare against controls.

BACKGROUND

The public awareness and usage of CAM have increased. The use of CAM has been described in patients with functional bowel disorders; however, their role in patients with gastrointestinal disease is less clear.

STUDY

Patients attending luminal gastroenterology clinics and customers at local supermarkets completed a 30-point, structured questionnaire assessing their use of CAM.

RESULTS

A total of 1,409 subjects were recruited. The incidence of CAM use was 49.5% for inflammatory bowel disease, 50.9% for irritable bowel syndrome, 20% for general gastrointestinal diseases, and 27% for controls. Pearson's chi(2) tests showed that patients with inflammatory bowel disease (IBD) or irritable bowel syndrome were more likely to use CAM than controls (P < 0.001). Binary logistic regression analysis showed that females were more likely to take CAM than men (P < 0.05).

CONCLUSIONS

The percentage of CAM users among patients with IBD is similar to those with a functional diagnosis. Increasing numbers of IBD patients are using CAM in addition to conventional therapy. Awareness of this may prevent adverse CAM and conventional drug interactions.

Cardiac morbidity and mortality related to orthotopic liver transplantation

This article briefly discusses the cardiac status of liver transplant recipients and their preoperative cardiac evaluation. It describes in detail perioperative and early and late postoperative complications as well as the cardiac problems associated with immunosuppression. The preoperative cardiovascular status of patients is important in determining how they cope with the stresses imposed by liver transplantation. Minor early cardiac events are common and may influence longer term cardiac morbidity. Immunosuppressive therapy may have short term effects but is likely to adversely affect long term cardiac risk.

Hepatopulmonary syndrome

The hepatopulmonary syndrom occurs when pulmonary microvacular dilatation causes hypoxemia in cirrhosis. It is found in between 15-20% of patients with chronic liver diseases and should be considered in the differential diagnosis of dyspnea or abnormal arterial oxygenation in this group. The presence of HPS appears to significantly increase mortality in affected patients with cirrhosis. The mediators of intrapulmonary vasodilatation and HPS are not fully characterized although pulmonary nitric oxide overproduction appears to be a key event in human and experimental models. Contrast echocardiography is the best screening test for pulmonary vasodilatation. Currently there are no effective medical therapies for HPS, although liver transplantation results in reversal of HPS in most cases. However, mortality is higher in patients with HPS undergoing transplantation relative to those without HPS.

Hepatopulmonary syndrome: role of nitric oxide and clinical aspects

Hepatopulmonary syndrome is defined by oxygenation impairment due to abnormal intrapulmonary vascular dilatations in patients with liver disease. The implication of enhanced pulmonary production of nitric oxide in the pathogenesis of intrapulmonary vascular dilatations has been demonstrated both in murine models and in human hepatopulmonary syndrome. The diagnosis of hepatopulmonary syndrome in chronic liver disease is of paramount importance, considering the fact that severe hypoxemia related to hepatopulmonary syndrome may occur in patients with well compensated liver disease and that survival is reduced in patients with hepatopulmonary syndrome relative to non hepatopulmonary syndrome patients. Priority for liver transplantation, which is presently the only cure, has been recently increased in patients with advanced hepatopulmonary syndrome.

ET-1 and TNF-alpha in HPS: analysis in prehepatic portal hypertension and biliary and nonbiliary cirrhosis in rats

Common bile duct ligation (CBDL) triggers a molecular cascade resulting in the hepatopulmonary syndrome (HPS). Both increased hepatic endothelin-1 (ET-1) production and pulmonary vascular ET(B) receptor expression with stimulation of endothelial nitric oxide synthase and TNF-alpha mediated inducible nitric oxide synthase and heme oxygenase-1 expression in pulmonary intravascular macrophages occur. Whether biliary cirrhosis is unique in triggering ET-1 and TNF-alpha alterations and HPS is unknown. We evaluated for HPS in rat prehepatic portal hypertension [partial portal vein ligation (PVL)], biliary (CBDL) and nonbiliary [thioacetamide treatment (TAA)] cirrhosis, and assessed ET-1 infusion in normal and PVL animals. Control, PVL, CBDL, TAA-treated, and ET-1-infused PVL animals had ET-1 and TNF-alpha levels measured and underwent molecular and physiological evaluation for HPS. HPS developed only in biliary cirrhosis in association with increased plasma ET-1 and TNF-alpha levels and the development of established molecular changes in the pulmonary microvasculature. In contrast, PVL did not increase ET-1 or TNF-alpha levels and TAA treatment increased TNF-alpha levels alone, and neither resulted in the full development of molecular or physiological changes of HPS despite portal pressure increases similar to those after CBDL. Exogenous ET-1 increased TNF-alpha levels and triggered HPS after PVL. Combination of ET-1 and TNF-alpha overproduction is unique to biliary cirrhosis and associated with experimental HPS. ET-1 infusion increases TNF-alpha levels and triggers HPS in prehepatic portal hypertension. ET-1 and TNF-alpha interact to trigger pulmonary microvascular changes in experimental HPS.

Retrospective analysis of the results of liver transplantation for adults with severe hepatopulmonary syndrome

The hepatopulmonary syndrome (HPS), consisting of elevated alveolar-arterial oxygen gradient and intrapulmonary vascular abnormalities in the presence of advanced liver disease, is associated with high mortality. Liver transplantation (LT) has been used for the treatment of HPS; however, the success of LT for the treatment of HPS is not uniformly documented. We reviewed our experience over a 5-year period and identified eight adult patients with incapacitating respiratory symptoms compatible with HPS. Inclusion criteria included hypoxemia, normal lung volumes, reduced oxygen diffusing capacity (D(L)CO), and the presence of intrapulmonary shunting. Underlying liver disease was caused by hepatitis C (2 patients), primary biliary cirrhosis (1 patient), cryptogenic cirrhosis (1 patient), alcohol (2 patients), and hepatitis C with alcohol (2 patients). Six out of eight patients required preoperative oxygen support. Severe hypoxemia was present in seven patients (Pa(O2) 51.5 +/- 8.2 mm Hg). Three patients had complicating pulmonary hypertension. All patients exhibited a severely reduced D(L)CO (44.6 +/- 12.2% of predicted value). Six patients were transplanted, with five requiring oxygen support at the time of discharge. Resolution of oxygen dependency occurred in all patients but was delayed in the two patients exhibiting complicating pulmonary hypertension (288.5 +/- 37.4 v 53.5 +/- 35.7 days). All patients exhibited O2 saturations greater than 98% on room air. Currently, three patients are alive and off oxygen. The current report documents successful resolution of hypoxemia after LT in this pilot cohort. This supports the newly implemented United Network for Organ Sharing (UNOS) criteria, that LT for HPS may be extended to include patients with Pa(O2) < 60 mm Hg.

Role of nitric oxide (NO) in pulmonary dysfunction associated with experimental cirrhosis

We examined the functional role of nitric oxide (NO) and nitric oxide synthase (NOS) isoforms in the pulmonary dysfunction seen in cirrhosis. Lungs were isolated from control and carbon tetrachloride (CCl(4))-induced cirrhotic rats and perfused at constant flow with a whole blood mixture. Ventilation with hypoxic gas resulted in attenuated hypoxic pulmonary vasoconstriction (HPV) in lungs from cirrhotic animals. Administration of the non-selective NOS inhibitor N-omega-Nitro-L-Arginine (L-NNA) resulted in HPV responses that were not different between groups. However, inhibition of inducible nitric oxide synthase (iNOS) did not restore cirrhotic HPV responses. Lungs from cirrhotic rats demonstrated enhanced endothelial-dependent vasodilation to vasopressin when preconstricted with hypoxia but not when preconstricted with thromboxane mimetic. Western blot analysis failed to demonstrate differences in pulmonary endothelial NOS (eNOS) or iNOS levels between groups. Our data suggest that, while NO may play a role in mediating the reduced pulmonary vasoreactivity observed in cirrhosis, other vasoactive factors are likely also important modulators of the pulmonary dysfunction seen in this disease.

Hepatopulmonary syndrome

Hepatopulmonary syndrome is caused by intrapulmonary vasodilation that leads to abnormal arterial gas exchange in the setting of liver disease or portal hypertension. It is seen in up to 15% of cirrhotics and is an increasingly common indication for liver transplantation. Testing for the presence of oxygenation abnormalities and intrapulmonary vasodilation is needed to make the diagnosis. Excess production of nitric oxide in the lung contributes to pulmonary vasodilation and may be triggered by the release of mediators from the damaged liver. No medical therapies are established as effective, and liver transplantation is the only documented curative treatment.