Carboxyhemoglobin levels in cirrhotic patients with and without hepatopulmonary syndrome

The pan-liver network theory: From traditional chinese medicine to western medicine

In traditional Chinese medicine (TCM), the liver is the "general organ" that is responsible for governing/maintaining the free flow of qi over the entire body and storing blood. According to the classic five elements theory, zang-xiang theory, yin-yang theory, meridians and collaterals theory, and the five-viscera correlation theory, the liver has essential relationships with many extrahepatic organs or tissues, such as the mother-child relationships between the liver and the heart, and the yin-yang and exterior-interior relationships between the liver and the gallbladder. The influences of the liver to the extrahepatic organs or tissues have been well-established when treating the extrahepatic diseases from the perspective of modulating the liver by using the ancient classic prescriptions of TCM and the acupuncture and moxibustion. In modern medicine, as the largest solid organ in the human body, the liver has the typical functions of filtration and storage of blood; metabolism of carbohydrates, fats, proteins, hormones, and foreign chemicals; formation of bile; storage of vitamins and iron; and formation of coagulation factors. The liver also has essential endocrine function, and acts as an immunological organ due to containing the resident immune cells. In the perspective of modern human anatomy, physiology, and pathophysiology, the liver has the organ interactions with the extrahepatic organs or tissues, for example, the gut, pancreas, adipose, skeletal muscle, heart, lung, kidney, brain, spleen, eyes, skin, bone, and sexual organs, through the circulation (including hemodynamics, redox signals, hepatokines, metabolites, and the translocation of microbiota or its products, such as endotoxins), the neural signals, or other forms of pathogenic factors, under normal or diseases status. The organ interactions centered on the liver not only influence the homeostasis of these indicated organs or tissues, but also contribute to the pathogenesis of cardiometabolic diseases (including obesity, type 2 diabetes mellitus, metabolic [dysfunction]-associated fatty liver diseases, and cardio-cerebrovascular diseases), pulmonary diseases, hyperuricemia and gout, chronic kidney disease, and male and female sexual dysfunction. Therefore, based on TCM and modern medicine, the liver has the bidirectional interaction with the extrahepatic organ or tissue, and this established bidirectional interaction system may further interact with another one or more extrahepatic organs/tissues, thus depicting a complex "pan-hepatic network" model. The pan-hepatic network acts as one of the essential mechanisms of homeostasis and the pathogenesis of diseases.

Prediction of Severe Esophageal Varices in Patients With Cirrhosis Based on Levitt's CO Breath Test: A Proof of Concept Study

GOALS

This study investigated the feasibility of using erythrocyte (RBC) lifespan determined by Levitt's CO breath test (LCOBT) to predict esophageal varices needing treatment (VNT) in patients with cirrhosis.

BACKGROUND

Esophageal varix bleeding is a common fatal complication of cirrhosis and portal hypertension. The gold standard for identifying VNT is esophagogastroduodenoscopy (EGD), an invasive procedure with low patient compliance. VNT screening based on Baveno VI criteria has mediocre specificity.

STUDY

RBC lifespan was determined by LCOBT in 53 cirrhotic patients (13 without varices, 11 mild/moderate varices, and 29 severe varices). Correlation of varix severity with RBC lifespan and other variables was analyzed. Rates of shortened RBC lifespan and thrombocytopenia (Baveno VI criteria) were compared.

RESULTS

RBC lifespan correlated inversely with severity of varices ( r =-0.793, P <0.001). Mean RBC lifespans were 129±31, 96±21, and 59±21 days for Nonvarix, Mild/Moderate, and Severe groups. Shortened RBC lifespan (<75 d) was observed in 79.3% (23/29) of patients with severe varices, a frequency similar or identical to thrombocytopenia rates [original Baveno VI criteria, 86.2% (25/29), P =0.487; expanded criteria, 79.3% (23/29), P >0.999]. Among 24 patients without severe varices, shortened RBC lifespan was observed in 1 patient whereas thrombocytopenia was detected in 13 and 8 patients based on the original ( P <0.001) and expanded criteria ( P =0.010), respectively.

CONCLUSIONS

RBC lifespan correlates inversely with varix severity in patients with cirrhosis. LCOBT may enable specific screening for VNT.

Hepatopulmonary syndrome: An update

Hepatopulmonary syndrome (HPS) is characterized by defects in oxygenation caused by intra-pulmonary vasodilation occurring because of chronic liver disease, portal hypertension, or congenital portosystemic shunts. Clinical implications of portal hypertension are very well-known, however, awareness of its effect on multiple organs such as the lungs are less known. The presence of HPS in chronic liver disease is associated with increased mortality. Medical therapies available for HPS have not been proven effective and definitive treatment for HPS is mainly liver transplantation (LT). LT improves mortality for patients with HPS drastically. This article provides a review on the definition, clinical presentation, diagnosis, and management of HPS.

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.

Impact of Liver Transplantation on Carbon Monoxide Production as Measured by Arterial Carboxyhemoglobin Levels in Cirrhotic Patients with and without Hepatopulmonary Syndrome

BACKGROUND Hepatic dysfunction is associated with increased production of carbon monoxide. End-stage liver disease patients with hepatopulmonary syndrome (HPS) have been shown to have higher blood carbon monoxide levels than those without HPS. The impact of liver transplantation on blood carbon monoxide levels is currently unknown. We assessed the impact of liver transplantation on blood carbon monoxide and whether this is affected by HPS. MATERIAL AND METHODS Eligible liver transplant recipients had room air arterial blood gas testing performed before and after liver transplantation. The carboxyhemoglobin fraction was obtained from arterial co-oximetry and used as a surrogate for carboxyhemoglobin production. Mean arterial carboxyhemoglobin fraction before transplantation was compared to that after transplantation. Mean absolute and median relative pre- to post-transplant within-patient change in carboxyhemoglobin fraction was compared between those with and without HPS. RESULTS Thirty-nine transplanted cirrhotic patients were analyzed, of whom 14 (36%) met criteria for hepatopulmonary syndrome. The mean pre-transplant carboxyhemoglobin fraction was higher than the post-transplant fraction (2.6 vs 1.8, difference 0.8 [95% CI 0.4-1.2]; P value 0.0002). Of the 14 patients with HPS, 11 (79%) experienced a decrease in their carboxyhemoglobin fraction after liver transplantation; among the 25 patients without HPS, 16 (64%) experienced such a decrease (P=0.48). Neither the absolute nor relative within-patient pre- to post-transplant change in carboxyhemoglobin fraction was significantly different between patients with and without HPS. CONCLUSIONS Blood carbon monoxide levels decreased significantly in cirrhotic patients following liver transplantation, but HPS did not affect the magnitude of this change.

Pathophysiological-based treatments of complications of cirrhosis

Detailed knowledge and understanding of the pathophysiological mechanisms and changes in hepatic and splanchnic function leading to the development of haemodynamic changes and portal hypertension in patients with cirrhosis are essential since it guides the search for targets to ameliorate liver-related abnormalities. Recent research has focused on the gut-liver axis, changes in intestinal permeability, translocation of bacterial products, and inflammation as important drivers of haemodynamic alterations and thereby targets for treatment. Additionally, treatment strategies should focus on microbiotic modulation, antiangiogenics, anti-inflammatory strategies, and modulation of bile acid metabolism. This paper aims to review contemporary pathophysiological-based treatment principles of the major complications of cirrhosis and portal hypertension and future targets for treatment.

Vascular syndromes in liver cirrhosis

Liver cirrhosis is associated with multiple vascular syndromes affecting almost all body systems. Many of these syndromes are directly related to impaired liver function and sometimes reversible after liver transplantation while others arise secondary to portal hypertension and ascites. Altered expression of angiogenic and vasoactive compounds (most importantly nitric oxide), endothelial dysfunction, dysregulated neurohormonal control, and systemic inflammatory state play differential roles in mediating homeostatic instability and abnormal vasogenic response. Important vascular features encountered in liver disease include portal hypertension, splanchnic overflow, abnormal angiogenesis and shunts, portopulmonary syndrome, hepatopulmonary syndrome, and systemic hyperdynamic circulation. Redistribution of effective circulatory volume deviating from vital organs and pooling in splanchnic circulation is also encountered in liver patients which may lead to devastating outcomes as hepatorenal syndrome. Etiologically, vascular syndromes are not isolated phenomena and vascular dysfunction in one system may lead to the development of another in a different system. This review focuses on understanding the pathophysiological factors underlying vascular syndromes related to chronic liver disease and the potential links among them. Many of these syndromes are associated with high mortality, thus it is crucial to look for early biomarkers for these syndromes and develop novel preventive and therapeutic strategies.

Pulse Oximetry Is Insensitive for Detection of Hepatopulmonary Syndrome in Patients Evaluated for Liver Transplantation

Screening for hepatopulmonary syndrome (HPS) using pulse oximetry is recommended in liver transplant (LT) candidates because mortality is increased, independently of the severity of the oxygenation defect. LT exception points may be afforded to those with HPS and severe hypoxemia. We assessed the screening characteristics of pulse oximetry for HPS. The Pulmonary Vascular Complications of Liver Disease 2 study is a multicenter, prospective cohort study of adults undergoing their first LT evaluation. Patients underwent protocolized assessment of oxygen saturation by pulse oximetry (SpO2 ), arterial blood gas, spirometry, and contrast-enhanced echocardiography (CE). HPS was defined as an alveolar-arterial gradient ≥15 mm Hg (≥20 mm Hg if age >64 years), intrapulmonary vascular dilatation on CE, and absence of lung disease. The study sample included 363 patients. Of these, 75 (20.7%; 95% confidence interval [CI], 16.6%-25.2%) met the criteria for HPS. The area under the receiver operating characteristic curve (or c-statistic) for SpO2 in discriminating HPS was 0.59 (95% CI, 0.51-0.66). An SpO2 <96%, recommended by practice guidelines as a threshold to require further testing, had low sensitivity (28%; 95% CI, 18%-28%). The c-statistic of SpO2 in discriminating HPS with a partial pressure of oxygen (PaO2 ) <60 mm Hg (eligible for LT exception points) was 0.76 (95% CI, 0.46-1.00). An SpO2 cutoff of <96% had higher sensitivity for detecting HPS with PaO2 <60 mm Hg (71%; 95% CI, 38%-100%) but was still inadequate. Conclusion: Pulse oximetry is not sufficiently sensitive to screen for HPS in LT candidates. Arterial blood gas and CE are required in LT candidates for diagnosis of HPS.

Potential Clinical Targets in Hepatopulmonary Syndrome: Lessons From Experimental Models

Hepatopulmonary syndrome (HPS) is a relatively common and potentially severe pulmonary complication of cirrhosis with increased risk of mortality. In experimental models, a complex interaction between pulmonary endothelial cells, monocytes, and the respiratory epithelium, which produces chemokines, cytokines, and angiogenic growth factors, causes alterations in the alveolar microvasculature, resulting in impaired oxygenation. Model systems are critical for evaluating mechanisms and for preclinical testing in HPS, due to the challenges of evaluating the lung in the setting of advanced liver disease in humans. This review provides an overview of current knowledge and recent findings in the rodent common bile duct ligation model of HPS, which recapitulates many features of human disease. We focus on the concepts of endothelial derangement, monocyte infiltration, angiogenesis, and alveolar type II cell dysfunction as main contributors and potential targets for therapy.

Raised plasma levels of H2S and nitrate predict intrapulmonary vascular dilations: A preliminary report in patients with cryptogenic cirrhosis

BACKGROUND AND AIMS

The role of vasoactive chemicals in the pathogenesis of hepatopulmonary syndrome (HPS), a disorder characterized by intrapulmonary vascular dilation (IPVD), is only vaguely elucidated. We aimed to study the association between plasma H₂S, nitrate levels, and presence and severity of IPVD and HPS.

METHODS

Consecutive adult patients with cryptogenic cirrhosis were evaluated for IPVD (by contrast echocardiography) and for hypoxemia (by arterial blood gas analysis). Plasma H₂S and nitrate levels were measured in these patients.

RESULTS

Fifty-eight patients with cryptogenic cirrhosis (male, 45; median age, range, 45, 16-74 years; Child's class; A, 30; B, 18; C, 10) were enrolled in this study. Thirty-four of the 58 (59%) patients had IPVD and 13 (22%) had HPS (mild, 4; moderate, 5; severe, 2; very severe, 2). Plasma H₂S levels were significantly higher in patients with IPVD (19.6, 5.7-83 μmol/L) as compared to patients who had no IPVD (12.3, 0-47 μmol/L; p-value 0.03) with an area under receiver operating characteristic curve of 0.68 (95% CI 0.53-0.84). Plasma H₂S levels were higher in patients with IPVD irrespective of liver disease severity. There was a trend for higher plasma nitrate levels in patients with IPVD (47, 15.8-126.4 nmol/mL) as compared to patients who had no IPVD (32.3, 6.9-51.4 nmol/mL; p-value 0.1). Raised plasma H₂S and nitrate levels had an additive effect on the presence of IPVD. Neither plasma H₂S nor plasma nitrate levels correlated with the degree of hypoxemia.

CONCLUSION

Raised plasma H₂S and nitrate levels predict the presence of IPVD in patients with cryptogenic cirrhosis.

Hepatopulmonary Disorders: Gas Exchange and Vascular Manifestations in Chronic Liver Disease

This review concentrates on the determinants of gas exchange abnormalities in liver-induced pulmonary vascular disorders, more specifically in the hepatopulmonary syndrome. Increased alveolar-arterial O₂ difference, with or without different levels of arterial hypoxemia, and reduced diffusing capacity represent the most characteristic gas exchange disturbances in the absence of cardiac and pulmonary comorbidities. Pulmonary gas exchange abnormalities in the hepatopulmonary syndrome are unique encompassing all three pulmonary factors determining arterial PO₂ , that is, ventilation-perfusion imbalance, increased intrapulmonary shunt and oxygen diffusion limitation that, combined, interplay with two relevant nonpulmonary determinants, that is, increased total ventilation and high cardiac output. Behind the complexity of this lung-liver association there is an abnormal pulmonary vascular tone that combines inhibition of hypoxic pulmonary vasoconstriction with a reduced (or blunted) hypoxic vascular response. The pathology and pathobiology include the presence of intrapulmonary vascular dilatations with or without pulmonary vascular remodeling, i.e. angiogenesis. Liver transplantation, the only effective therapeutic approach to successfully improve and resolve the vast majority of complications induced by the hepatopulmonary syndrome, along with a large list of frustrating pharmacologic interventions, are also reviewed. Another liver-induced pulmonary vascular disorder with less gas exchange involvement, such as portopulmonary hypertension, is also considered. © 2018 American Physiological Society. Compr Physiol 8:711-729, 2018.

Cryptogenic Cirrhosis and Hepatopulmonary Syndrome in a Boy with Hepatic Hemangioma in Botswana: A Case Report and Review of the Literature

Hepatic hemangiomas are considered to be the most common benign tumors of the liver. They are often found incidentally while investigating for other causes of liver disease. Hemangiomas that are less than 10 cm are not expected to cause any problems. Typically, they do not enlarge and, apart from regular follow-up, no definitive treatment is indicated. This is a posthumous case report of a male child with a medium-sized hemangioma from infancy, complicated by cryptogenic cirrhosis and hepatopulmonary syndrome. It demonstrates the challenges of managing a child with such complicated conditions in a resource-limited setting.

Hepatopulmonary syndrome is associated with the presence of hepatocellular carcinoma in patients with decompensated cirrhosis

Background

Hepatopulmonary syndrome (HPS) is a relatively common complication in patients with decompensated cirrhosis. Our aim was to evaluate the prevalence of HPS, its clinical impact, and the possible association between HPS and characteristics of patients with decompensated cirrhosis.

Methods

Patients with stable decompensated cirrhosis admitted to our department and assessed for HPS were included. For each patient, several clinical, laboratory and echocardiographic parameters as well as renal function were recorded. The severity of liver disease was evaluated according to the Model for End-stage Liver Disease and Child-Pugh scores, and renal function was assessed using ⁵¹chromium complexed with ethylene diamine tetracetic acid. In addition, the short synacthen test was performed in each patient to evaluate the adrenal function.

Results

Sixty-three patients were enrolled, 26 (41.3%) of whom diagnosed with HPS. In multivariate analysis, the presence of hepatocellular carcinoma [odds ratio (OR) 8.1, 95% confidence interval (CI) 5.3-27.9, P=0.045] and salivary cortisol at T60 (60 min after the intravenous injection of 250 μg corticotropin) (OR 0.88, 95%CI 0.71-0.98, P=0.045) were the factors independently associated with HPS. T60 salivary cortisol had relatively good discriminative ability for the presence of HPS (area under the curve=0.73). The presence of HPS was not associated with the outcome (P=0.22).

Conclusion

In our cohort of patients with decompensated cirrhosis, the presence of hepatocellular carcinoma and T60 salivary cortisol were the only factors independently associated with HPS.

Emerging hepatic syndromes: pathophysiology, diagnosis and treatment

Liver cirrhosis is a major cause of morbidity and mortality worldwide, mainly due to complications of portal hypertension. In this article, we review the current understanding on the pathophysiology, the diagnostic criteria and the available therapeutic options for patients with emerging hepatic syndromes in cirrhosis, namely the hepatorenal, hepato-adrenal and hepatopulmonary syndrome. The hepatorenal syndrome is a well-recognized complication of advanced cirrhosis and is usually associated with an accelerated course to death unless liver transplantation is performed. The hepatopulmonary syndrome is often missed in the evaluation of patients with cirrhosis; however, early recognition is essential for the efficient management of individual patients. The hepato-adrenal syndrome, although not fully characterized, offers an exciting field for research and potential therapeutic interventions.

Hepatopulmonary Syndrome and Liver Transplantation: A Recent Review of the Literature

A severe and common pulmonary vascular complication of liver disease is hepatopulmonary syndrome (HPS). It is a triad of liver dysfunction and/or portal hypertension, intrapulmonary vascular dilatations, and increased alveolar-arterial oxygen gradient. Prevalence varies according to various study groups from 4%-47%. While the most common presenting symptom of HPS is dyspnea, it is usually asymptomatic, and thus all liver transplant candidates should be screened for its presence. Pulse oximetry is a useful screening method, but arterial blood gas examination is the gold standard. If there is an abnormal P (A-a)O2 gradient, microbubble transthoracic echocardiography should be done for diagnosis. Outcome is unpredictable, and there is currently no effective medical therapy. The only effective therapy is considered to be liver transplantation. Complete resolution of HPS after liver transplantation is seen within a year in most HPS patients.

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.

Von Willebrand factor antigen for detection of hepatopulmonary syndrome in patients with cirrhosis

BACKGROUND & AIMS

Hepatopulmonary syndrome (HPS) occurs in 20-30% of patients with liver cirrhosis and is associated with a >2 fold increased mortality. Endothelial dysfunction seems to play a central role in its pathogenesis. von Willebrand factor antigen (vWF-Ag), an established marker of endothelial dysfunction, is significantly elevated in patients with liver cirrhosis, portal hypertension, and in experimental HPS. Aim of the present study was to evaluate the impact of vWF-Ag as a screening marker for presence of HPS in patients with stable cirrhosis.

METHODS

145 patients with stable liver cirrhosis were screened for presence of HPS in this prospective cohort type cross sectional diagnostic study. vWF-Ag and SaO2 levels were assessed at time of screening for HPS. Criteria of HPS were fulfilled in 31 (21%) patients.

RESULTS

vWF-Ag levels were significantly higher in patients with HPS compared to patients without HPS (p<0.001). Furthermore, vWF-Ag correlated significantly with gas exchange in HPS positive patients (p<0.05). vWF-Ag is an independent predictor of HPS after correction for sex, age, model for endstage-liver disease (MELD), and hepatic venous pressure gradient (HVPG) (OR per 1% increase of vWF-Ag: 1.02, 95% CI: 1.00-1.04, p<0.05). The best cut-off was 328% at a sensitivity of 100% and specificity of 53.5%; positive predictive value: 36.9%; negative predictive value: 100%.

CONCLUSIONS

HPS is associated with elevated vWF-Ag levels. vWF-Ag may be a useful screening tool for early detection of HPS. Further studies investigating vWF-Ag in HPS will be needed to confirm our findings.

Cirrhosis and hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) is characterized as a triad: liver disease, intrapulmonary vascular dilatation and arterial hypoxemia. HPS is reported to be present in 4% to 32% of adult patients with end-stage liver disease and in 9%-20% of children. The pathogenesis of HPS has not been clearly identified. Portal hypertension causes impairment in the perfusion of the bowel and increases the enteral translocation of Gram (-) bacteria and endotoxins. This stimulates the release of vasoactive mediators, such as tumor necrosis factor-alpha, heme oxygenase-derived carbon monoxide and nitric oxide. Genetic alterations have not been associated with this syndrome yet; however, cytokines and chemokines have been suggested to play a role. Recently, it was reported that cumulated monocytes lead to the activation of vascular endothelial growth factor-dependent signaling pathways and pulmonary angiogenesis, which plays an important role in HPS pathogenesis. At present, the most effective and only radical treatment is a liver transplant (LT). Cirrhotic patients who are on the waiting list for an LT have a shorter survival period if they develop HPS. Therefore, it is suggested that all cirrhotic cases should be followed closely for HPS and they should have priority in the waiting list.

Liver in cardiopulmonary disease

Hepatopulmonary syndrome (HPS) and portopulmonary hypertension (PoPH) are two fascinating and incompletely understood pulmonary vascular conditions seen in the setting of cirrhotic patients. Of the two HPS is more common and is primarily caused by pulmonary vasodilatation resulting in hypoxaemia and hyperdynamic circulation. PoPH is less common and conversely, pulmonary vasoconstriction and vascular remodelling occurs resulting in increased pulmonary vascular resistance. However, both conditions can co-exist and it is usually PoPH which develops in a patient with pre-existing HPS. Although these two pulmonary conditions are not common complications of chronic liver diseases, the treatment options are mainly limited to liver transplantation. Cirrhotic cardiomyopathy is closely related to haemodynamic changes in portal hypertension. The key features are normal cardiac pressures at rest, with reduced ability to compensate for physiological or iatrogenic stresses such as drug therapy or TIPSS. There is no effective therapy and outcomes after liver transplantation are variable.

Hepatopulmonary syndrome: update on recent advances in pathophysiology, investigation, and treatment

Hepatopulmonary syndrome (HPS) is an important cause of dyspnea and hypoxia in the setting of liver disease, occurring in 10-30% of patients with cirrhosis. It is due to vasodilation and angiogenesis in the pulmonary vascular bed, which leads to ventilation-perfusion mismatching, diffusion limitation to oxygen exchange, and arteriovenous shunting. There is evidence, primarily from animal studies, that vasodilation is mediated by a number of endogenous vasoactive molecules, including endothelin-1 and nitric oxide (NO). In experimental HPS, liver injury stimulates release of endothelin-1 and results in increased expression of ET(B) receptors on pulmonary endothelial cells, leading to upregulation of endothelial NO synthase (eNOS) and subsequent increased production of NO, which causes vasodilation. In addition, increased phagocytosis of bacterial endotoxin in the lung not only promotes stimulation of inducible NO synthase, which increases NO production, but also contributes to intrapulmonary accumulation of monocytes, which may stimulate angiogenesis via vascular endothelial growth factor pathway. Despite these insights into the pathogenesis of experimental HPS, there is no established medical therapy, and liver transplantation remains the main treatment for symptomatic HPS, although selected patients may benefit from other surgical or radiological interventions. In this review, we focus on recent advances in our understanding of the pathophysiology of HPS, and discuss current approaches to the investigation and treatment of this condition.

The role of CX₃CL1/CX₃CR1 in pulmonary angiogenesis and intravascular monocyte accumulation in rat experimental hepatopulmonary syndrome

BACKGROUND & AIMS

Hepatopulmonary syndrome (HPS), classically attributed to intrapulmonary vascular dilatation, occurs in 15-30% of cirrhotics and causes hypoxemia and increases mortality. In experimental HPS after common bile duct ligation (CBDL), monocytes adhere in the lung vasculature and produce vascular endothelial growth factor (VEGF)-A and angiogenesis ensues and contribute to abnormal gas exchange. However, the mechanisms for these events are unknown. The chemokine fractalkine (CX(3)CL1) can directly mediate monocyte adhesion and activate VEGF-A and angiogenesis via its receptor CX(3)CR1 on monocytes and endothelium during inflammatory angiogenesis. We explored whether pulmonary CX(3)CL1/CX(3)CR1 alterations occur after CBDL and influence pulmonary angiogenesis and HPS.

METHODS

Pulmonary CX(3)CL1/CX(3)CR1 expression and localization, CX(3)CL1 signaling pathway activation, monocyte accumulation, and development of angiogenesis and HPS were assessed in 2- and 4-week CBDL animals. The effects of a neutralizing antibody to CX(3)CR1 (anti-CX(3)CR1 Ab) on HPS after CBDL were evaluated.

RESULTS

Circulating CX(3)CL1 levels and lung expression of CX(3)CL1 and CX(3)CR1 in intravascular monocytes and microvascular endothelium increased in 2- and 4-week CBDL animals as HPS developed. These events were accompanied by pulmonary angiogenesis, monocyte accumulation, activation of CX(3)CL1 mediated signaling pathways (Akt, ERK) and increased VEGF-A expression and signaling. Anti-CX(3)CR1 Ab treatment reduced monocyte accumulation, decreased lung angiogenesis and improved HPS. These events were accompanied by inhibition of CX(3)CL1 signaling pathways and a reduction in VEGF-A expression and signaling.

CONCLUSIONS

Circulating CX(3)CL1 levels and pulmonary CX(3)CL1/CX(3)CR1 expression and signaling increase after CBDL and contribute to pulmonary intravascular monocyte accumulation, angiogenesis and development of experimental HPS.

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.

Occurrence of hepatopulmonary syndrome in patients with cirrhosis who are candidates for liver transplantation

OBJECTIVE

To determine the occurrence of hepatopulmonary syndrome (HPS) in patients with cirrhosis who are candidates for liver transplantation; to compare demographic, clinical, laboratory, and spirometric characteristics, as well as echocardiography results, arterial blood gas analysis, and severity of liver disease between the groups of patients with and without HPS; and to describe the occurrence of HPS in the subgroup of patients with cirrhosis and schistosomiasis mansoni (mixed liver disease).

METHODS

Between January and November of 2007, we evaluated 44 patients under treatment at the Liver Transplant Outpatient Clinic of the Federal University of Pernambuco Hospital das Clínicas, in the city of Recife, Brazil. The diagnostic criteria for HPS were intrapulmonary vascular dilatation, identified by transthoracic echocardiography, and an alveolar-arterial oxygen tension difference >or= 15 mmHg or a PaO2 < 80 mmHg.

RESULTS

The mean age of the patients was 52 years, and 31 patients (70%) were male. The most common cause of cirrhosis was alcohol use. Schistosomiasis was present in 28 patients (64%). Of the 44 patients, 20 (45.5%) were diagnosed with HPS. No significant differences were found between those patients and the patients without HPS in terms of any of the characteristics studied. Of the 28 patients with cirrhosis and schistosomiasis, 10 (35.7%) were diagnosed with HPS.

CONCLUSIONS

In the population studied, HPS was highly prevalent and did not correlate with any of the variables analyzed.

Alterations in plasma carbon monoxide levels and alveolar permeability in cirrhotic rats

AIM: To examine possible alterations in plasma carbon monoxide (CO) levels and alveolar permeability in rats with carbon tetrachloride-induced cirrhosis.

METHODS: Liver cirrhosis was induced in rats by subcutaneous administration of carbon tetrachloride. Mean arterial pressure (MAP, kPa), heart rate (HR, b/min), and portal pressure (PP, cm/H₂O) were monitored by using an indwelling catheter. Plasma CO levels were determined by Chalmers method, and alveolar permeability was measured using the Evens blue extravasation technique.

RESULTS: Typical features of cirrhosis were histologically observed in carbon tetrachloride-treated rats. Compared with normal control rats, cirrhotic rats presented a significant increase in portal pressure (16.67 cmH₂O ± 0.63 cmH₂O vs 8.82 cmH₂O ± 0.29 cmH₂O; P < 0.01), plasma CO levels (18.69 μmol/L ± 1.86 μmol/L vs 10.27 μmol/L ± 1.21 μmol/L; P < 0.01), and Evens blue extravasation (36.57 μg/g ± 1.69 μg/g vs 29.83 μg/g ± 2.34 μg/g; P < 0.01), but a significant decrease in mean arterial pressure (15.92 kPa ± 0.74 kPa vs 18.93 kPa ± 0.71 kPa; P < 0.01).

CONCLUSION: Activation of the HO-CO system and increased alveolar permeability may be important causes of development of hepatopulmonary syndrome in patients with cirrhosis.

Genetic risk factors for hepatopulmonary syndrome in patients with advanced liver disease

BACKGROUND & AIMS

Hepatopulmonary syndrome (HPS) affects 10%-30% of patients with cirrhosis and portal hypertension and significantly increases mortality. Studies in experimental models indicate that pulmonary angiogenesis contributes to the development of HPS, but pathogenesis in humans is poorly understood. We investigated genetic risk factors for HPS in patients with advanced liver disease.

METHODS

We performed a multicenter case-control study of patients with cirrhosis being evaluated for liver transplantation. Cases had an alveolar-arterial oxygen gradient > or = 15 mm Hg (or > or =20 mm Hg if age > 64 years) and contrast echocardiography with late appearance of microbubbles after venous injection of agitated saline (intrapulmonary vasodilatation); controls did not meet both criteria for case status. The study sample included 59 cases and 126 controls. We genotyped 1086 common single nucleotide polymorphisms (SNPs) in 94 candidate genes.

RESULTS

Forty-two SNPs in 21 genes were significantly associated with HPS after adjustments for race and smoking. Eight genes had at least 2 SNPs associated with disease: CAV3, ENG, NOX4, ESR2, VWF, RUNX1, COL18A1, and TIE1. For example, rs237872 in CAV3 showed an odds ratio of 2.75 (95% confidence interval: 1.65-4.60, P = .0001) and rs4837192 in ENG showed an odds ratio of 0.35 (95% confidence interval: 0.14-0.89, P = .027). Furthermore, variation in CAV3 and RUNX1 was associated with HPS in gene-based analyses.

CONCLUSIONS

Polymorphisms in genes involved in the regulation of angiogenesis are associated with the risk of HPS. Further investigation of these biologic pathways might elucidate the mechanisms that mediate the development of HPS in certain patients with severe liver disease.

Losartan prevents portal hypertension-induced, redox-mediated endothelial dysfunction in the mesenteric artery in rats

BACKGROUND & AIMS

Advanced stages of portal hypertension are characterized by generalized vasodilatation and a hyperdynamic syndrome that leads to complications such as hepatopulmonary syndrome. We assessed the endothelial function--particularly the formation of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF)--in rats following common bile duct ligation (CBDL) to determine the underlying mechanisms of these processes.

METHODS

Reactivity of mesenteric artery rings from male Wistar rats was determined in organ chambers. The expression levels of connexins (Cx) (Cx37, Cx40, Cx43), intermediate and small conductance Ca(2+)-activated K(+) channels (IK(Ca), SK(Ca)), endothelial NO synthase (eNOS), NADPH oxidase subunits, and nitrotyrosines were assessed by immunohistochemistry in mesenteric and pulmonary arteries. The vascular formation of reactive oxygen species (ROS) was evaluated using dihydroethidine. Control rats or those that had undergone CBDL were given either the NADPH oxidase inhibitor apocynin or the angiotensin II receptor type 1 antagonist losartan.

RESULTS

Decreased EDHF-mediated relaxations to acetylcholine and red wine polyphenols were observed in CBDL rats, compared with controls, whereas the level of NO-mediated relaxation was similar. Impaired EDHF-mediated relaxations were associated with reduced vascular expression of Cx37, Cx40, Cx43, IK(Ca) and SK(Ca); increased expression of eNOS and NADPH oxidase subunits; and increased vascular formation of ROS and peroxynitrites. These effects were prevented by exposure to apocynin or losartan.

CONCLUSIONS

CBDL is associated with reduced EDHF-mediated relaxations in the mesenteric artery, whereas NO-mediated relaxations persisted. These findings indicate that impaired EDHF-mediated relaxation involves an excessive vascular oxidative stress, most likely following activation of angiotensin II type 1 receptors.

Hepatopulmonary syndrome: an update

Hepatopulmonary syndrome (HPS) is a clinical threesome composed of liver disease, intrapulmonary vascular dilatation (IPVD) and arterial gas abnormalities. Its occurrence has been described in up to 32% of cirrhotic candidates for liver transplantation. It also affects non-cirrhotic patients with portal hypertension. Its pathogenesis is not well defined, but an association of factors such as imbalance in the endothelin receptor response, pulmonary microvascular remodeling and genetic predisposition is thought to lead to IPVD. Diagnosis is based on imaging methods that identify these dilatations, such as contrast echocardiography or perfusion scintigraphy with 99mTc, as well as analysis of arterial gases to identify elevated alveolar-arterial differences in O2 or hypoxemia. There is no effective pharmacological treatment and complete resolution only occurs through liver transplantation. The importance of diagnosing HPS lies in prioritizing transplant candidates, since presence of HPS is associated with worse prognosis. The aim of this paper was to review the pathogenetic theories and current diagnostic criteria regarding HPS, and to critically analyze the prioritization of patients with HPS on the liver transplant waiting list. Searches were carried out in the Medline (Medical Literature Analysis and Retrieval System Online) via PubMed, Cochrane Library and Lilacs (Literatura Latino-Americana e do Caribe em Ciências da Saúde) databases for articles published between January 2002 and December 2007 involving adults and written either in English or in Portuguese, using the term hepatopulmonary syndrome. The studies of greatest relevance were included in the review, along with text books and articles cited in references that were obtained through the review.

Pulmonary angiogenesis in a rat model of hepatopulmonary syndrome

BACKGROUND & AIMS

Hepatopulmonary syndrome (HPS), defined as intrapulmonary vasodilation, occurs in 10%-30% of cirrhotics and increases mortality. In a rat model of HPS induced by common bile duct ligation (CBDL), but not thioacetamide (TAA)-induced nonbiliary cirrhosis, lung capillary density increases, monocytes accumulate in the microvasculature, and signaling factors in the angiogenesis pathway (Akt and endothelial nitric oxide synthase [eNOS]) are activated. Pentoxifylline (PTX) directly decreases lung endothelial Akt and eNOS activation, blocks intravascular monocyte accumulation, and improves experimental HPS; we evaluated whether pulmonary angiogenesis develops in this model.

METHODS

TAA- and PTX-treated animals were evaluated following CBDL. Lung angiogenesis was assessed by quantifying factor VIII-positive microvessels and levels of von Willebrand factor (vWf), vascular endothelial cadherin (VE-cadherin), and proliferating cell nuclear antigen (PCNA). Angiogenic factors including phospho-Akt, phospho-eNOS, vascular endothelial growth factor (VEGF)-A, and phospho-VEGF receptor-2 (p-VEGFR-2) were compared and monocyte accumulation was assessed.

RESULTS

Following CBDL, but not TAA exposure, rats developed HPS that was temporally correlated with increased numbers of lung microvessel; increased levels of vWf, VE-cadherin and PCNA; and activation of Akt and eNOS. Angiogenesis was accompanied by increased pulmonary VEGF-A and p-VEGFR-2 levels, with VEGF-A staining in accumulated intravascular monocytes and alveolar endothelial cells. Following CBDL, PTX-treated rats had reduced numbers of microvessels, reduced lung monocyte accumulation, downregulation of pulmonary angiogenic factors, and reduced symptoms of HPS.

CONCLUSIONS

A specific increase in pulmonary angiogenesis occurs as experimental HPS develops, accompanied by activation of VEGF-A-associated angiogenic pathways. PTX decreases the angiogenesis, reduces the symptoms of HPS, and downregulates VEGF-A mediated pathways.

Natural heme oxygenase-1 inducers in hepatobiliary function

Many physiological effects of natural antioxidants, their extracts or their major active components, have been reported in recent decades. Most of these compounds are characterized by a phenolic structure, similar to that of α-tocopherol, and present antioxidant properties that have been demonstrated both in vitro and in vivo. Polyphenols may increase the capacity of endogenous antioxidant defences and modulate the cellular redox state. Changes in the cellular redox state may have wide-ranging consequences for cellular growth and differentiation. The majority of in vitro and in vivo studies conducted so far have attributed the protective effect of bioactive polyphenols to their chemical reactivity toward free radicals and their capacity to prevent the oxidation of important intracellular components. However, in recent years a possible novel aspect in the mode of action of these compounds has been suggested; that is, the ultimate stimulation of the heme oxygenase-1 (HO-1) pathway is likely to account for the established and powerful antioxidant/anti-inflammatory properties of these polyphenols. The products of the HO-catalyzed reaction, particularly carbon monoxide (CO) and biliverdin/bilirubin have been shown to exert protective effects in several organs against oxidative and other noxious stimuli. In this context, it is interesting to note that induction of HO-1 expression by means of natural compounds contributes to protection against liver damage in various experimental models. The focus of this review is on the significance of targeted induction of HO-1 as a potential therapeutic strategy to protect the liver against various stressors in several pathological conditions.

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.

Carbon monoxide in sepsis

Despite modern practices in critical care medicine, sepsis or systemic inflammatory response syndrome remains a leading cause of morbidity and mortality in the intensive care unit. Thus, the need to identify new therapeutic tools for the treatment of sepsis is urgent. In this context, carbon monoxide has become a promising therapeutic molecule that can potentially prevent uncontrolled inflammation in sepsis. In humans, carbon monoxide arises endogenously from the degradation of heme by heme oxygenase enzymes. Both endogenously synthesized and exogenously applied carbon monoxide can exert antiinflammatory and antiapoptotic effects in cells and tissues. Based on these properties, carbon monoxide, when applied at low concentration, conferred protection in a variety of cellular and rodent models of sepsis, and furthermore reduced morbidity and mortality in vivo. Therefore, application of carbon monoxide may have a major impact on the future of sepsis treatment. This review summarizes evidence for salutary effects of carbon monoxide in sepsis of various organs, including lung, heart, kidney, liver, and intestine, and discusses the potential translation of the data into human clinical trials.

Splanchnic and systemic vasodilatation: the patient

Arterial vasodilatation is one of the most important characteristics of cirrrhosis and portal hyptertension. Nowadays, it has been known that progressive vasodilatation is an essential factor contributing to hyperdynamic circulation and multiple organ dysfunction in liver cirrhosis. Over the past decades, numerous investigations have originated from the clinical observations. Clinicians and investigators have learned and applied new concepts of the pathophysiology of portal hypertension. For example, we now have effective pharmacologic treatment for hepatorenal syndrome. This review summarizes the developement of progressive vasodilatation syndrome in liver cirrhosis and portal hypertension with focus on the patients.

Utility of pulse oximetry screening for hepatopulmonary syndrome

BACKGROUND & AIMS

Hepatopulmonary syndrome is characterized by oxygenation abnormalities caused by intrapulmonary vasodilatation in the setting of liver disease and/or portal hypertension. This syndrome occurs in approximately 15%-30% of cirrhotic patients and influences mortality and transplant candidacy. However, no specific screening guidelines are established. We evaluated pulse oximetry with contrast echocardiography in detecting hepatopulmonary syndrome in a cohort of patients undergoing evaluation for liver transplantation.

METHODS

One hundred twenty-seven consecutive patients referred for liver transplantation evaluation were prospectively enrolled and underwent pulse oximetry, contrast echocardiography, and arterial blood gas measurements on room air. Demographic, clinical, and laboratory data were recorded and analyzed.

RESULTS

Forty-one (32%) patients were found to have hepatopulmonary syndrome. There were no significant differences in demographic or clinical features compared with patients without hepatopulmonary syndrome, with the exception of pulse oximetry and oxygenation abnormalities. With a threshold value of <96%, pulse oximetry had a sensitivity and specificity of 100% and 88%, respectively, for detecting patients with a partial pressure of oxygen <60 mm Hg. Receiver operator characteristic analysis revealed that a pulse oximetry value of < or =94% detected all patients with a partial pressure of oxygen <60 mm Hg with an increased specificity of 93%. In addition, higher pulse oximetry thresholds reliably identified HPS patients with less severe hypoxemia, albeit with lower specificity.

CONCLUSIONS

Pulse oximetry is a simple, low cost, and widely available technique that reliably predicts the presence and severity of hypoxemia in patients with hepatopulmonary syndrome. Institution of pulse oximetry screening might enhance detection and improve management of hepatopulmonary syndrome in cirrhosis.

[Carbon monoxide--poison or potential therapeutic?]

Carbon monoxide (CO) is much more than just a toxic gas. Carbon monoxide is produced endogenously by the enzyme heme oxygenase and has important functions under physiological and pathophysiological conditions. Recent studies suggested antioxidative, anti-inflammatory, antiproliferative, anti-apoptotic, and vasodilating characteristics. Regarding clinically-relevant diseases in anesthesiology and critical care medicine, such as adult respiratory distress syndrome (ARDS), sepsis, or during organ transplantation, cytoprotective properties have been demonstrated by low-dose CO in experimental models. In view of a potential CO application in future human studies, this review discusses what is known to date about CO as it relates to functional, protective and toxic aspects.

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.

Contribution of CARD15 variants in determining susceptibility to Crohn's disease in Sweden

OBJECTIVE

Crohn's disease (CD) is a chronic inflammatory bowel disorder caused by environmental and genetic factors. Mutations in the CARD15 gene have been associated with CD. No previous case-control CARD15 study has been performed in the Swedish population.

MATERIAL AND METHODS

The study comprised of 321 individuals: 178 with CD and 143 healthy controls (HCs), all from Stockholm County. All were genotyped for the three main CD-associated CARD15 variants (R702W, G908R and 1007fs) and phenotypic associations were investigated.

RESULTS

The allele frequencies of the R702W variant (4.5% CD versus 0.7% HC, p=0.008, OR = 6.8) and the G908R variant (2.0% CD versus 0% HC, p=0.045) were more common in CD patients than in controls. No significant difference in1007fs variant allele frequency was found between CD patients and controls (2.0% CD versus 1.7% HC, p = 0.8, OR = 1.1). Carriage of CARD15 variants was more common in the CD patients than in controls (15.2% CD versus 4.2% HC, p = 0.001, OR = 4.1, population attributable risk (PAR) = 11.4%). Genotype-phenotype analysis demonstrated that CARD15 variants were associated with ileal disease (p=0.0006, OR = 9.3, CI = 2.2-34) and protective for colonic CD (p = 0.01, OR = 0.18). An association between CARD15 variants and ileal CD (p=0.004, OR = 6.6) was confirmed by multivariate analyses.

CONCLUSIONS

The CARD15 variants R702W and G908R, but not 1007fs, are associated with susceptibility to CD in Stockholm County. Genotype-phenotype analysis shows an association with ileal CD. The contribution of these CARD15 mutations in Swedish CD patients overall is low in relation to studies elsewhere in Central Europe and North America, but is consistent with emerging data from elsewhere in Scandinavia and in Northern Europe.

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.

Adeno-associated virus-mediated heme oxygenase-1 gene transfer suppresses the progression of micronodular cirrhosis in rats

AIM: To test the hypothesis that enhancement of the activity of heme oxygenase can interfere with processes of fibrogenesis associated with recurrent liver injury, we investigated the therapeutic potential of over-expression of heme oxygense-1 in a CCl₄-induced micronodular cirrhosis model.

METHODS: Recombinant adeno-associated viruses carrying rat HO-1 or GFP gene were generated. 1×10¹² vg of adeno-associated viruses were administered through portal injection at the time of the induction of liver fibrosis.

RESULTS: Conditioning the rat liver with over-expression of HO-1 by rAAV/HO-1 significantly increased the HO enzymatic activities in a stable manner. The development of micronodular cirrhosis was significantly inhibited in rAAV/HO-1-transduced animals as compared to controls. Portal hypertension was markedly diminished in rAAV/HO-1-transduced animals as compared to controls, whereas there are no significant changes in systolic blood pressure. This finding was accompanied with improved liver biochemistry, less infiltrating macrophages and less activated hepatic stellate cells (HSCs) in rAAV/HO-1-transduced livers.

CONCLUSIONS: Enhancement of HO activity in the livers suppresses the development of cirrhosis.