Pulmonary blood transit time and impaired arterial oxygenation in patients with chronic liver disease

COVID-19-associated liver injury: Adding fuel to the flame

COVID-19 is mainly characterized by respiratory disorders and progresses to multiple organ involvement in severe cases. With expansion of COVID-19 and SARS-CoV-2 research, correlative liver injury has been revealed. It is speculated that COVID-19 patients exhibited abnormal liver function, as previously observed in the SARS and MERS pandemics. Furthermore, patients with underlying diseases such as chronic liver disease are more susceptible to SARS-CoV-2 and indicate a poor prognosis accompanied by respiratory symptoms, systemic inflammation, or metabolic diseases. Therefore, COVID-19 has the potential to impair liver function, while individuals with preexisting liver disease suffer from much worse infected conditions. COVID-19 related liver injury may be owing to direct cytopathic effect, immune dysfunction, gut-liver axis interaction, and inappropriate medication use. However, discussions on these issues are infancy. Expanding research have revealed that angiotensin converting enzyme 2 (ACE2) expression mediated the combination of virus and target cells, iron metabolism participated in the virus life cycle and the fate of target cells, and amino acid metabolism regulated immune response in the host cells, which are all closely related to liver health. Further exploration holds great significance in elucidating the pathogenesis, facilitating drug development, and advancing clinical treatment of COVID-19-related liver injury. This article provides a review of the clinical and laboratory hepatic characteristics in COVID-19 patients, describes the etiology and impact of liver injury, and discusses potential pathophysiological mechanisms.

Pulmonary transit time has close relation with pulmonary pulse wave transit time in normal subjects

BACKGROUND

Pulmonary transit time (PTT) and pulmonary pulse wave transit time (pPTT) are useful parameters for the evaluation of cardiopulmonary circulation and vascular alterations, but their relationship remains unknown. The aim of this study was to investigate the correlation between PTT and pPTT.

METHODS

A total of 60 healthy volunteers were involved in this study. They were divided into two groups (30 participants per group): <50 years and >50 years. They all underwent Doppler echocardiography of pulmonary vein flow and contrast echocardiography with the measurement of pPTT and PTT, respectively. The correlation between PTT and pPTT was deduced.

RESULTS

Compared with Group of <50 years, there was a significant increment in left atrial volume index, left atrial pressure and pulmonary artery stiffness but a significant reduction in acceleration times of pulmonary artery flow in Group of >50 years (p < 0.05). Group >50 years had longer PTT and but reduced normalized PTT by R-R interval (NPTT), reduced normalized pPTT by R-R interval (NpPTT) than Group <50 years (p < 0.05), while there was no significant difference in pPTT between the two groups (p > 0.05). PTT and NPTT were all negatively correlated with pPTT and NpPTT. The statistically significant strongest correlation was observed between PTT and NpPTT (r = -0.886, p < 0.0001). The regression equation for them was y = 7.4396-13.095x (R²  = 0.785; p < 0.001), where x and y represent NpPTT and PTT, respectively.

CONCLUSION

PTT had close relation with pPTT in normal subjects. From the regression equation for them, we can get the value of PTT simply and easily by non-invasively measured pPTT.

Advances in Diagnostic Imaging of Hepatopulmonary Syndrome

Hepatopulmonary syndrome (HPS) is a serious pulmonary complication of progressive liver disease that leads to a poor clinical prognosis. Patients with HPS may develop acute respiratory failure, which requires intensive care and therapy. At present, the only effective treatment is liver transplantation; therefore, early diagnosis and timely treatment are of considerable significance. The three main features of HPS are liver disease, oxygenation disorder, and intrapulmonary vascular dilatation (IPVD). Diagnosing HPS is challenging due to the difficulty in detecting the presence or absence of IPVD. As such, imaging examination is very important for detecting IPVD. This paper reviews the imaging methods for diagnosing HPS such as ultrasound, dynamic pulmonary perfusion imaging, pulmonary angiography, and computed tomography.

Pulmonary manifestations of chronic liver disease: a comprehensive review

Hepatopulmonary syndrome (HPS) and porto-pulmonary hypertension (PoPH) represent relatively common pulmonary vascular complications of advanced liver disease. Despite distinct differences in their pathogenetic background, both clinical states are characterized by impaired arterial oxygenation and limited functional status, and are associated with increased pre-transplantation mortality. Accumulation of ascitic fluid in the pleural cavity, known as hepatic hydrothorax (HH), is another frequent manifestation of decompensated cirrhosis, which may cause severe respiratory dysfunction, depending on the volume of the effusion, the rapidity of its development and its resistance to therapeutic measures. Orthotopic liver transplantation constitutes the only effective treatment able to resolve the pulmonary complications of liver disease. A prioritization policy for liver transplantation has evolved over the past years regarding advanced stages of HPS, yielding favorable outcomes regarding post-transplantation survival and HPS resolution. In contrast, severe PoPH is associated with poor post-transplantation survival. Hence, liver transplantation is recommended only for patients with PoPH and an acceptable reduction in pulmonary pressure values, after receiving PoPH-targeted vasodilating therapy. This review focuses on basic pathogenetic and diagnostic principles and discusses the current therapeutic approaches regarding HPS, PoPH, and HH.

Cardiac Imaging in Liver Transplantation Candidates: Current Knowledge and Future Perspectives

Cardiovascular dysfunction in cirrhotic patients is a recognized clinical entity commonly referred to as cirrhotic cardiomyopathy. Systematic inflammation, autonomic dysfunction, and activation of vasodilatory factors lead to hyperdynamic circulation with high cardiac output and low peripheral vascular resistance. Counter acting mechanisms as well as direct effects on cardiac cells led to systolic or diastolic dysfunction and electromechanical abnormalities, which are usually masked at rest but exposed at stress situations. While cardiovascular complications and mortality are common in patients undergoing liver transplantation, they cannot be adequately predicted by conventional cardiac examination including transthoracic echocardiography. Newer echocardiography indices and other imaging modalities such as cardiac magnetic resonance have shown increased diagnostic accuracy with predictive implications in cardiovascular diseases. The scope of this review was to describe the role of cardiac imaging in the preoperative assessment of liver transplantation candidates with comprehensive analysis of the future perspectives anticipated by the use of newer echocardiography indices and cardiac magnetic resonance applications.

Pulmonary transit time derived from pulmonary angiography for the diagnosis of hepatopulmonary syndrome

BACKGROUND & AIMS

Pulmonary transit time (PTT) is the transit time of blood from the right side of the heart to the left side of the heart. The aim of the present study was to evaluate the role of the PTT derived from pulmonary angiography in the diagnosis of hepatopulmonary syndrome (HPS).

METHODS

From December 2014 to September 2015, all patients with chronic liver disease and/or portal hypertension undergoing a venous interventional radiologic procedure at our institution were eligible for inclusion in this prospective study. Pulmonary angiography was performed in all patients, and the PTT, which was defined as the time between opacification of the pulmonary trunk and the right border of the left atrium, was determined.

RESULTS

A total of 53 patients were included, 20 of whom had a positive contrast-enhanced echocardiography result and an elevated alveolar-arterial oxygen gradient were considered to have HPS. PTT was significantly shorter in patients with HPS than in those without [median, 3.34 (interquartile range, 3.01-3.67) seconds vs 4.0 (interquartile range, 3.67-4.17) seconds; P < .001]. The area under the receiver operating characteristic curve of PTT for diagnosing HPS was 0.83 (95% confidence interval, 0.70-0.92). The optimal cut-off value of PTT for diagnosing HPS, based on Youden's index, was 3.55 seconds. The sensitivity, specificity and accuracy of PTT < 3.55 seconds for diagnosing HPS were 70%, 85% and 79% respectively.

CONCLUSIONS

Pulmonary transit time derived from pulmonary angiography is useful for diagnosing HPS, especially for patients with intracardiac shunts and inadequate echocardiographic windows.

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.

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.

A case report of suspected hepatopulmonary syndrome secondary to ductal plate malformation with chronic active hepatitis in a dog

Hepatopulmonary syndrome (HPS) is a respiratory complication of hepatic disease, that is well recognized in humans and defined by the presence of 1) liver disease, 2) hypoxemia and/or high alveolar-arterial oxygen gradient (AaDO₂) and 3) intrapulmonary vasodilatation. The present report describes a similar case of HPS in a dog. A six-month-old Papillon was diagnosed with ductal plate malformation with chronic active hepatitis and showed progressive increases in AaDO₂ over the course of the following six months. The presence of intrapulmonary vasodilatation was confirmed by agitated saline contrast transthoracic echocardiography. Also, the absence of congenital cardiac defect was confirmed by transthoracic echocardiography. From these results, we suspected that this dog had HPS. This is the first description of suspected canine HPS.

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.

Response to exercise in patients with liver cirrhosis: implications for liver transplantation

End-stage liver cirrhosis is a systemic disease carrying a short-term desperate prognosis without liver transplantation. Given the discrepancy between the growing number of candidates and the limited available liver grafts, the pre-transplantation screening process has become a challenging task. Cardiopulmonary exercise testing, by measuring maximal oxygen consumption at peak exercise, provides a global integrative approach of the health status of an individual. In the setting of liver cirrhosis, decreased oxygen consumption at peak exercise may result from a combination of multiple extra-hepatic complications, including deconditioning, malnutrition-associated muscle weakness, anaemia, cirrhotic cardiomyopathy, and hepato-pulmonary syndrome for instance. In addition, oxygen consumption at peak exercise not only correlated with the severity of the liver disease, but it is also independently associated with survival following liver transplantation. The present article aims to review the numerous determinants of impaired aerobic capacity in patients with severe liver disease, and to discuss how useful is cardiopulmonary exercise testing as a critical tool in the pre-transplantation assessment of these patients.

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 characteristics of respiratory function and pulmonary hemodynamics in patients with portal hypertension

OBJECTIVE

To investigate the respiratory function and pulmonary hemodynamics in patients with portal hypertension (PHT).

METHODS

A total of 148 patients with PHT were divided into three groups according to Child-Pugh classification. Results of blood biochemistry test, lung function test, arterial blood gas analysis, free portal pressure (FPP) and pulmonary hemodynamics measurements of the three Child-Pugh grade groups were compared with those of the control group.

RESULTS

The overall incidence of arterial hypoxemia was 27.0% in PHT patients. Arterial oxygen tension (PaO(2) ) had a significant negative correlation with FPP (r=-0.76, P<0.01) and Child-Pugh grade (r=-0.42, P<0.01), as well as a positive correlation with systemic vascular resistance (SVR, r=0.24, P=0.01). Alveolar-arterial oxygen difference (A-aDO(2) ) increased in Child-Pugh grade C group when compared with Child-Pugh grade A and B groups (P<0.05). Restrictive impairment of lung function was seen in Child-Pugh grade C group. Direct measurement of the hemodynamics in PHT patients revealed a hyperdynamic disturbance in both systemic and portal venous systems, and was illustrated in pulmonary circulation as an increase of mean pulmonary arterial pressure (MPAP) and pulmonary arterial wedged pressure (PAWP) as well as a decrease of pulmonary vascular resistance (PVR).

CONCLUSIONS

  High output and low resistance are the key characteristics of pulmonary circulation in PHT patients and the decrease of PVR can be detected even when liver function is still compensated.

Management of cardiopulmonary complications of cirrhosis

Advanced portal hypertension accompanying end-stage liver disease results in an altered milieu due to inadequate detoxification of blood from splanchnic circulation by the failing liver. The portosystemic shunts with hepatic dysfunction result in an increased absorption and impaired neutralisation of the gastrointestinal bacteria and endotoxins leads to altered homeostasis with multiorgan dysfunction. The important cardiopulmonary complications are cirrhotic cardiomyopathy, hepatopulmonary syndrome, portopulmonary hypertension, and right-sided hydrothorax.

Clinical study on pulmonary diffusion function in patients with chronic liver disease

OBJECTIVE

To investigate the influence of chronic liver disease (CLD) on pulmonary diffusion function.

METHODS

Arterial blood gas analysis, pulmonary function test, contrast-enhanced transthoracic echocardiography and technetium macro-aggregated albumin scanning were performed in 50 cirrhotic patients who underwent surgery on portal hypertension and liver transplantation. The severity of chronic liver disease (CLD) was evaluated by Child-Pugh-Turcotte (CPT) categorization and model for end stage liver disease (MELD) score from October 2008 to July 2009 in our surgical department and organ transplantation center.

RESULTS

A-aDO(2) was increased with the aggravation of liver dysfunction. The pulmonary diffusion capacity for carbon monoxide (DLCO) differed significantly among the three groups, which was (90.8 ± 7.3)% in CPT A group, (82.8 ± 10.8)% in CPT B group, and (73.5 ± 8.3)% in CPT C group. A-aDO(2) correlated positively with CPT (r= 0.581, P= 0.000) as well as the MELD score (r= 0.696, P= 0.000), whereas DLCO was negatively correlated with CPT (r=-0.630, P= 0.000) and the MELD score (r=-0.708, P= 0.000).

CONCLUSION

DLCO can be useful in the detection of pulmonary vascular abnormality of CLD. The MELD score may be a better criterion than the CPT score in assessing intrapulmonary vascular damage of CLD patients.

Pulmonary dysfunction and hepatopulmonary syndrome in cirrhosis and portal hypertension

BACKGROUND

Pulmonary dysfunction including the hepatopulmonary syndrome (HPS) is an important complication to cirrhosis and portal hypertension. However, the precise relation to liver dysfunction and the prevalence of HPS are unclear.

AIMS

We therefore aimed to assess (i) the prevalence of HPS in consecutive alcoholic cirrhotic patients, (ii) the degree of pulmonary dysfunction in relation to liver function and (iii) the response of a 100% oxygen test on cardiopulmonary and peripheral oxygenation.

METHODS

Fifty patients with cirrhosis and 12 matched healthy controls were entered in this study. All underwent haemodynamic and pulmonary investigations [lung diffusing capacity for carbon monoxide (DLCO), contrast-enhanced echocardiography and detection of extrapulmonary shunt fraction]. A 100% oxygen test was performed with the assessment of arterial oxygen tension (PaO(2)), the alveolar-arterial oxygen gradient (AaPO(2)) and peripheral transcutaneous oxygen tension (tcPO(2)).

RESULTS

The prevalence of HPS was 10%. PaO(2) and DLCO were reduced in 32 and 72% and AaPO(2), was increased in 60% of the patients respectively. DLCO correlated with indicators of liver dysfunction (galactose elimination capacity, P<0.01, indocyanine green clearance, P<0.001), portal hypertension (post-sinusoidal resistance, P<0.01) and central hypovolaemia (central and arterial blood volume, P<0.01). After 100% oxygen inhalation, the changes in PaO(2), AaPO(2), tcPO(2) and heart rate were abnormal in the patients compared with controls (P<0.02).

CONCLUSIONS

Pulmonary dysfunction in alcoholic cirrhosis is common and relates to different aspects of liver dysfunction, whereas the prevalence of HPS is low. The haemodynamic response to oxygen inhalation is clearly impaired and HPS and pulmonary dysfunction seem to be caused by different pathophysiological mechanisms.

Inhaled iloprost for hepatopulmonary syndrome: improvement of hypoxemia

Hepatopulmonary syndrome is characterized by advanced liver disease, hypoxemia, and intrapulmonary shunting. The only reported curative option is orthotopic liver transplantation. We describe here a beneficial effect of inhaled prostacyclin including a decrease in respiratory symptoms and improved oxygenation in this clinical situation, with no approved pharmacological long-term therapy. The prostanoid iloprost, approved for pulmonary and portopulmonary hypertension, caused an increase in oxygenation, relief of dyspnea, and increased exercise tolerance in a patient suffering from liver-cirrhosis-associated hepatopulmonary syndrome. After liver transplantation, restitution of hepatopulmonary syndrome did not occur immediately. Inhaling iloprost resulted in improved physical condition and better clinical rehabilitation potential until hypoxemia finally resolved 3 months after transplantation. Therefore, iloprost could improve quality of life in patients with hepatopulmonary syndrome waiting for liver transplantation and post surgery until the resolution of the hypoxemia.

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.

Pulmonary blood volume and transit time in cirrhosis: relation to lung function

BACKGROUND/AIMS

In cirrhosis a systemic vasodilatation leads to an abnormal distribution of the blood volume with a contracted central blood volume. In addition, the patients have a ventilation/perfusion imbalance with a low diffusing capacity. As the size of the pulmonary blood volume (PBV) has not been determined separately we assessed PBV and pulmonary transit time (PTT) in relation to lung function in patients with cirrhosis and in controls.

METHODS

Pulmonary and cardiac haemodynamics and transit times were determined by radionuclide techniques in 22 patients with alcoholic cirrhosis and in 12 controls. The lung function including diffusing capacity for carbon monoxide (DL, CO) was determined by conventional single breath technique.

RESULTS

In the patients, PTT was shorter, 3.9+/-1.2 vs 5.7+/-1.0 s in the controls, P<0.001, and the PBV was lower, 362+/-151 vs 587+/-263 ml, in the controls, P<0.005. Both PTT and PBV were lowest in patients with advanced disease. DL, CO was reduced in the patients and correlated significantly with PTT (r=0.58, P=0.007) and PBV (r=0.49, P<0.03).

CONCLUSIONS

The results suggest that the reduced PBV contributes to the reduced effective blood volume in cirrhosis. The relation between PBV and PTT and the low diffusing capacity suggests the pulmonary vascular compartment as an important element in the pathophysiology of the lung dysfunction in cirrhosis.

Portopulmonary hypertension

Portopulmonary hypertension (PPHT) is defined as precapillary pulmonary hypertension accompanied by hepatic disease or portal hypertension. Pulmonary hypertension results from excessive pulmonary vascular remodeling and vasoconstriction. These histological alterations have been indistinguishable from those of other forms of pulmonary arterial hypertension. Factors involved in the pathogenesis of PPHT include volume overload, hyperdynamic circulation, and circulating vasoactive mediators. The disorder has a substantial impact on survival and requires focused treatment. Liver transplantation in patients with moderate to severe PPHT is associated with a significantly reduced survival rate. The best medical treatment for patients with PPHT is controversial; most authors currently regard continuous intravenous application of prostacyclin as the treatment of choice for patients with severe PPHT. There is only very limited reported experience with inhaled prostacyclin or its analog, iloprost. Increasing evidence of the efficacy of the endothelin-receptor antagonist bosentan and of the phosphodiesterase-5 inhibitor sildenafil is emerging in highly selected patients with PPHT. In the future, a combination therapy of the above-mentioned agents might become a therapeutic option. Other agents such as beta-blockers seem to be harmful to patients with moderate to severe portopulmonary hypertension. Up-to-date, randomized, double-blind, controlled clinical trials are lacking and are needed urgently.

The diagnosis and treatment of hepatopulmonary syndrome

Few prognostic indicators and outcomes reported for patients who have hepatopulmonary syndrome can be consistently reproduced between institutions. The lack of practice recommendations based upon consistent and predictable outcomes creates uncertainty for physicians trying to make the best patient choices. With the scarcity of donor organs, these issues are of particular importance when transplantation in considered as a treatment option. Much uncertainty arises from the basic tasks of making an accurate diagnosis in patients who have symptoms suggestive of hepatopulmonary syndrome. This article focuses on problems that underlie diagnostic accuracy and uses this information to appraise critically outcomes literature.

The hyperdynamic circulation of chronic liver diseases: from the patient to the molecule

The hyperdynamic circulatory syndrome observed in chronic liver diseases is a great example of research that originated from clinical observations and progressed in the last 50 years from the patient to the experimental laboratory. Our knowledge has evolved from the patient to the molecule, using experimental models that serve as a source for understanding the complex pathophysiological mechanisms that govern this complex syndrome. We now know that progressive vasodilatation is central to the detrimental effects observed in multiple organs. Although nitric oxide has been shown to be the primary vasodilator molecule in these effects, other molecules also participate in the complex mechanisms of vasodilatation. This review summarizes three major areas: first, clinical observation in patients; second, experimental models used to study the hyperdynamic circulatory syndrome; and third, the vasodilator molecules that play roles in vascular abnormalities observed in portal hypertension.

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.

Arterial hypoxemia and intrapulmonary vasodilatation in rat models of portal hypertension

BACKGROUND

Rats with chronic bile duct ligation (CBDL) and portal vein ligation (PVL) are used as models of portal hypertension. CBDL rats show hypoxemia with intrapulmonary vasodilatation (IPVD), and are recognized as a model of hepatopulmonary syndrome (HPS), while PVL rats are normoxemic. We investigated the differences in arterial oxygenation between these models, and the key factors leading to HPS.

METHODS

Forty-eight Sprague-Dawley rats were prepared as CBDL or PVL models, or as Sham rats. Arterial oxygenation, hemodynamics (reference sample method), and IPVD were simultaneously evaluated in conscious and unrestrained animals, using (141)Ce- or (113)Sn-labeled microspheres (15 microm in diameter), respectively. Endothelin-1 (ET-1) and nitrate/nitrite (end products of nitric oxide; NOx) production by the lung tissue (increment across the lungs) was also determined.

RESULTS

The extent of IPVD was similar in both models, but hypoxemia was only observed in CBDL rats. The ET-1 level and the increment in NOx were significantly increased in CBDL rats, and the increment was directly correlated with impairment of oxygenation. Blood flow through the bronchial arteries (anatomical shunting) was increased in CBDL rats, reaching more than three times the level in PVL rats or Sham rats.

CONCLUSIONS

These results support the hypothesis that NO derived from the lung tissues contributes to hypoxemia, and IPVD appears to be a prerequisite for impaired oxygenation. The considerable increase of anatomical shunting may potentially contribute to impaired oxygenation in CBDL rats.