Histometrical investigation of the pulmonary artery in severe hepatic disease

Is pulmonary arterial hypertension associated with schistosomiasis distinct from pulmonary arterial hypertension associated with portal hypertension?

Pulmonary arterial hypertension associated with schistosomiasis (SchPAH) and pulmonary arterial hypertension associated with portal hypertension (PoPAH) are lung diseases that develop in the presence of liver diseases. However, mechanistic pathways by which the underlying liver conditions and other drivers contribute to the development and progression of pulmonary arterial hypertension (PAH) are unclear for both etiologies. In turn, these unknowns limit certainty of strategies to prevent, diagnose, and reverse the resultant PAH. Here we consider specific mechanisms that contribute to SchPAH and PoPAH, identifying those that may be shared and those that appear to be unique to each etiology, in the hope that this exploration will both highlight known causal drivers and identify knowledge gaps appropriate for future research. Overall, the key pathophysiologic differences that we identify between SchPAH and PoPAH suggest that they are not variants of a single condition.

Pulmonary function testing in patients with liver cirrhosis (Review)

Liver cirrhosis is a common long-term outcome of chronic hepatic inflammation. Patients with liver cirrhosis may also have pulmonary complications. There are several reasons for pulmonary dysfunction in liver cirrhosis, including intrinsic cardiopulmonary dysfunction unrelated to liver disease and specific disorders related to the presence of liver cirrhosis and/or portal hypertension. The most prevalent and clinically significant pulmonary complications are hepatic hydrothorax, hepatopulmonary syndrome, spontaneous pulmonary empyema and portopulmonary hypertension. Pulmonary function tests (PFTs) have traditionally been used to assess the lung function of patients with liver cirrhosis. To the best of our knowledge, the present review is the first to detail all types of PFTs performed in patients with liver cirrhosis and discuss their clinical significance. Patients with liver cirrhosis have reduced values of spirometric parameters, diffusion capacity for carbon monoxide (DLCO), lung volumes, maximal inspiratory pressure and maximal expiratory pressure. Furthermore, they have a higher closing volume, a greater airway occlusion pressure 0.1 sec after the onset of inspiratory flow and greater exhaled nitric oxide values. In order to improve pulmonary function, patients with ascites may require therapeutic paracentesis. Such findings should be considered when evaluating individuals with liver disease, particularly those who may require surgery. Poor lung function, particularly restrictive lung disease, can have an impact on post-transplant outcomes, such as ventilator time, length of hospital duration and post-operative pulmonary complications; thus, the transplant care team needs to be aware of its prevalence and relevance.

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.

Anesthesia for Patients with Concomitant Hepatic and Pulmonary Dysfunction

Hepatic function and pulmonary function are interrelated with failure of one organ system affecting the other. With improved therapies, patients with concomitant hepatic and pulmonary failure increasingly enjoy a good quality of life and life expectancy. Therefore, the prevalence of such patients is increasing with more presenting for both emergent and elective surgical procedures. Hypoxemia requires a thorough evaluation in patients with end-stage liver disease. The most common etiologies respond to appropriate therapy. Portopulmonary hypertension and hepatopulmonary syndrome are associated with increased perioperative morbidity and mortality. It is incumbent on the anesthesiologist to understand the physiology of liver failure and its early effect on pulmonary function to ensure a successful outcome.

Portopulmonary hypertension

Portopulmonary hypertension (POPH) is the presence of pulmonary arterial hypertension in patients with portal hypertension. Among liver transplant (LT) candidates, reported incidence rates of POPH range from 4.5% to 8.5%. In patients with LT, intraoperative death and immediate post-LT mortality are feared clinical events when transplantation is attempted in the setting of untreated, moderate to severe POPH; therefore, POPH precludes LT unless the mean pulmonary artery pressure can be reduced to a safe level and right ventricular function optimized. Specific pulmonary artery vasodilator medications seem effective in reducing pulmonary artery pressures and improving right ventricular function and survival.

Preoperative Assessment and Management of Liver Transplant Candidates With Portopulmonary Hypertension

Pulmonary artery hypertension (PAH) that occurs as a consequence of portal hypertension is termed portopulmonary hypertension (POPH) and is associated with significant morbidity and mortality. Among liver transplant (LT) candidates, reported incidence rates of POPH range from 4.5% to 8.5%. The severity of POPH is unrelated to the severity of portal hypertension or the liver disease. In LT patients, intraoperative death and immediate post-LT mortality are feared clinical events when transplantation is attempted in the setting of untreated, moderate to severe POPH. Specific pulmonary artery vasodilator medications (PAH-specific therapy) appear effective in reducing pulmonary artery pressures, improving right ventricular (RV) function and survival. Thus, screening for and accurately diagnosing POPH prior to LT has become a standard of care. The post-LT course of patients with moderate POPH is unpredictable, but most patients can be weaned from PAH-specific therapy over time. In this article, we present an overview of the preoperative assessment of POPH with an emphasis on risk assessment for transplant and the most recent medical treatment options.

Relationship between liver cirrhosis and pulmonary function impairment

AIM: To determine the relationship between liver cirrhosis and pulmonary function impairment.

METHODS: Fifty patients with liver cirrhosis, who were treated at our hospital and the First Affiliated Hospital of Sun Yat-Sen University from May 2007 to March 2008, were included in the study. All patients underwent pulmonary function tests (PFTs) to assess forced expiratory volume in one second (FEV₁), FEV₁/FVC (forced vital capacity), single-breath carbon monoxide diffusing capacity (DLCO) and DLCO per unit of alveolar volume (KCO, also known as DLCO/VA). The mean FEV1, FEV1/FVC, DLCO and KCO were compared between patients with and without liver palm, spider naevi, clinical jaundice, hypoproteinemia, hypersplenism or widening of the portal vein, respectively.

RESULTS: Approximately 34 percent of patients presented with ventilation abnormalities, mainly restrictive ventilation disorders. Decreased diffusion capacity was the most common pulmonary function disorder and was found in 72% of patients. The Child-Pugh score was correlated inversely with KCO (r = -0.351, P < 0.05). Serum albumin level was correlated positively with FEV₁ and KCO (r = 0.334 and 0.336, respectively; both P < 0.05). The width of the portal vein was correlated inversely with FEV₁ and DLCO (r = -0.389 and -0.417, respectively; both P < 0.05). The thickness of the spleen was correlated inversely with DLCO and KCO (r = -0.644 and -0.536, respectively; both P < 0.01). Hemoglobin concentration and the thickness of the spleen were independent predictors of DLCO (P < 0.05).

CONCLUSION: The impairment of diffusion capacity is a very common disorder in patients with liver cirrhosis. Long-term portal hypertension is closely associated with the development of impaired diffusion capacity in patients with liver cirrhosis.

Nitric oxide and carbon monoxide lung transfer in patients with advanced liver cirrhosis

In advanced cirrhosis, decreased lung transfer for carbon monoxide (TLCO) and increased alveolar-arterial oxygen tension difference (PA-aO2 ≥15 mmHg while breathing ambient air) are frequently detected. Pulmonary membrane diffusion capacity for CO (DmCO) and pulmonary capillary blood volume (Vcap) can be derived from the simultaneous measurement of TLCO and lung transfer for nitric oxide (TLNO). Measurements of single-breath TLNO and TLCO were performed in 49 cirrhotic patients with advanced liver cirrhosis and in 35 healthy controls to derive Vcap, DmCO, and TLNO:TLCO ratio. Twenty-five patients had increased PA-aO2, of whom 11 had hepatopulmonary syndrome (HPS). Compared with controls, non-HPS patients with normal PA-aO2 had a significant ∼10% decrease in TLCO, DmCO, and Vcap but similar TLNO:TLCO ratios. Compared with non-HPS patients with normal PA-aO2, non-HPS patients with increased PA-aO2 had lower Vcap and higher TLNO:TLCO ratio but similar DmCO. HPS patients had lower Vcap and higher TLNO:TLCO ratios than both subgroups of non-HPS patients. In cirrhotic patients, TLNO:TLCO ratios correlated positively, and TLCO (percentage of the predicted value) and Vcap (percentage of the predicted value) correlated negatively with PA-aO2 ( r2 = 0.25, P = 0.0003, r2 = 0.48, P < 0.0001 and r2 = 0.57, P < 0.0001, respectively). We concluded that, in cirrhotic patients, lower TLCO and increased PA-aO2 are associated with lower Vcap. In addition, high TLNO:TLCO ratios in patients with increased PA-aO2 suggest a decreased thickness of the capillary blood layer in these patients.

Sustained low diffusing capacity in hepatopulmonary syndrome after liver transplantation

AIM: To study the presence of sustained low diffusing capacity (DL_CO) after liver transplantation (LT) in patients with hepatopulmonary syndrome (HPS).

METHODS: Six patients with mild-to-severe HPS and 24 without HPS who underwent LT were prospectively followed before and after LT at mid-term (median, 15 mo). HPS patients were also assessed at long-tem (median, 86 mo).

RESULTS: Before LT, HPS patients showed lower PaO₂ (71 ± 8 mmHg), higher AaPO₂ (43 ± 10 mmHg) and lower DL_CO (54% ± 9% predicted), due to a combination of moderate-to-severe ventilation-perfusion (V_A/Q) imbalance, mild shunt and diffusion limitation, than non-HPS patients (94 ± 4 mmHg and 19 ± 3 mmHg, and 85% ± 3% predicted, respectively) (P < 0.05 each). Seven non-HPS patients had also reduced DL_CO (70% ± 4% predicted).

At mid- and long-term after LT, compared to pre-LT, HPS patients normalized PaO₂ (91 ± 3 mmHg and 87 ± 5 mmHg), AaPO₂ (14 ± 3 mmHg and 23 ± 5 mmHg) and all V_A/Q descriptors (P < 0.05 each) without changes in DL_CO (53% ± 8% and 56% ± 7% predicted, respectively). Post-LT DL_CO in non-HPS patients with pre-LT low DL_CO was unchanged (75% ± 6% predicted).

CONCLUSION: While complete V_A/Q resolution in HPS indicates a reversible functional disturbance, sustained low DL_CO after LT also present in some non-HPS patients, points to persistence of sub-clinical liver-induced pulmonary vascular changes.

The biological "scrabble" of pulmonary arteriovenous malformations: considerations in the setting of cavopulmonary surgery

Pulmonary arteriovenous fistulas are vascular malformations, which, by virtue of producing abnormal vascular connections proximal to the units of gas exchange, result in intrapulmonary right-to-left shunting. These malformations or fistulas reflect at least in part disordered angiogenesis, and less commonly recruitment and dilation of pre-existing vascular channels. Pulmonary arteriovenous fistulas occur in a number of diverse clinical settings. Such fistulas are a well-established feature of the Weber-Osler-Rendu complex, or hereditary haemorrhagic telangiectasia, an autosomal dominant vascular dysplasia characterized by mucocutaneous telangiectasis, epistaxis, gastrointestinal haemorrhage, and arteriovenous malformations in the lung, brain, liver and elsewhere. They are also seen in the patient with acute or chronic liver disease, disease that is usually but not invariably severe, or those with non-cirrhotic portal hypertension. They may occur as congenital malformations, single or diffuse, large or small in isolation, and when large or extensive enough may result in hypoxaemia, clinical cyanosis, and heart failure. Cerebral vascular accidents are also a well-known complication of this disorder. An extensive literature has accumulated with regard to the pulmonary arteriovenous fistulas seen in the setting of the Weber-Osler-Rendu complex, and there is considerable information on the genetics, basic biology, clinical findings, complications and therapeutic interventions of these malformations in the setting of this syndrome. These issues, however, are not the primary considerations of this review, although some aspects of this fascinating disorder will be discussed later. Rather the focus will be on pulmonary arteriovenous malformations that develop in the setting of cavopulmonary surgery, and their relationship to the pulmonary arteriovenous fistulas occurring in the hepatopulmonary syndrome. The complex tapestry of these overlapping and intersecting clinical observations will be unfolded in the light of their chronology.

Cirrhosis of the liver and receptor-mediated function in vascular smooth muscle

Altered regulation of receptors on the vascular smooth muscle has been proposed as one of the mechanisms that may account for the vascular abnormalities in patients with cirrhosis of the liver. Impaired contractility and down-regulation of contractile receptors have been demonstrated in cirrhotic patients and animal models, although interpretation of the literature is hampered by methodological variation and conflicting results. There is little evidence, however, that receptor down-regulation is the cause of contractile dysfunction in either patients or animal models. Receptor desensitisation may contribute to impaired contraction in human arteries, but further investigation is required to confirm this possibility.

High prevalence of pulmonary diffusion abnormalities without interstitial changes in long-term survivors of liver transplantation

Abnormalities in lung function are frequent findings in patients with terminal stage chronic liver disease. While spirometric parameters improve early after liver transplantation, a reduction in diffusion capacity has been reported up to 15 months after transplantation. It is unknown to what extent this disturbance in gas exchange occurs among long term survivors after liver transplantation. We assessed lung function in terms of spirometry, and gas exchange as well as pulmonary morphology by high resolution computed tomography (HRCT) in 40 patients 38 months (median, range 20-147 months) after liver transplantation. The prevalence of restrictive or obstructive changes was not different from predicted values. For the whole group of long-term survivors the carbon monoxide transfer coefficient (KCO) was reduced to 71.3 + 12.0% predicted (P < 0.05). HRCT revealed interstitial changes in only 2/40 (5.0%), emphysematous bullae in 2/40 (5.0%) and pleural thickening in 9/40 (22.5%). Diffusion abnormalities are prevalent in the majority of patients after liver transplantation, whereas spirometric abnormalities are absent also in the long term. The high prevalence of impaired gas exchange and the absence of interstitial lesions imply that changes in pulmonary blood vessels are the most likely cause.

Portopulmonary hypertension and the liver transplant candidate

The management of the liver transplant (OLT) candidate with portopulmonary hypertension (PPHTN) has dramatically changed in the past 3 years. Careful preoperative evaluation with functional characterization of right ventricular function plays a critical role. The pulmonary vascular response to epoprostenol infusion serves as a deciding factor for OLT candidacy. Careful perioperative attention to avoid right ventricular failure from acutely elevated pulmonary artery pressures or sudden increases in right ventricular preload is a key physiologic tenet of management. With increased surgical expertise, anesthetic sophistication, and availability of epoprostenol, PPHTN is no longer considered an absolute contraindication for OLT.

Pulmonary vascular morphological changes in cirrhotic patients undergoing liver transplantation

Cirrhosis and portal hypertension may be associated with pulmonary hypertension and pulmonary dysfunction. However, morphological pulmonary vascular lesions in patients with cirrhosis have not been well characterized morphometrically. We morphometrically evaluated pulmonary vessels in liver transplant recipients with pretransplantation cirrhosis and correlated our findings with pretransplantation cardiopulmonary function, postoperative course, and postmortem cardiopulmonary findings. Autopsy lung slides from 23 transplant recipients with pretransplantation cirrhosis were examined. External vessel diameter, intimal thickness, and arterial medial thickness were measured with a micrometer after pentachrome staining. The percent of total diameter comprised by intima or media was calculated for each vessel. Medical records were reviewed for smoking history, pretransplantation cardiopulmonary function testing, and postoperative course. Autopsy cases without liver or significant cardiopulmonary diseases, matched for age, sex, and smoking history, served as controls. Transplant recipients had significantly more pulmonary venous intimal thickening than matched controls (P <.0001). Sixty-five percent (15 of 23) of these patients had some degree of pretransplantation pulmonary dysfunction, defined by abnormalities in pulmonary function tests, oxygen saturation, and/or increased pulmonary artery pressures. However, the severity of venous intimal thickening did not correlate with the severity of pretransplantation pulmonary dysfunction. Arterial intimal and medial thickness were not statistically significantly different from controls. Pulmonary venous intimal thickening and resultant luminal impingement are morphological findings not previously described in this population. The arterial lesion, when present, is similar to that seen in pulmonary hypertension from other causes. These pulmonary vascular lesions may be implicated in pulmonary dysfunction in patients with cirrhosis and may be associated with increased posttransplantation cardiopulmonary morbidity and mortality.

Severe pulmonary hypertension and amelioration of hepatopulmonary syndrome after liver transplantation

A patient with end-stage liver disease as a result of alpha1-antitripsin deficiency presented for orthotopic liver transplantation. The liver cirrhosis was complicated by portal hypertension and hepatopulmonary syndrome resulting in varicosities and severe hypoxia (room air oxygen saturation 69%). After transplantation, the hepatopulmonary syndrome improved but, over the next 14 months, the patient developed severe pulmonary hypertension. Six years posttransplantation, his room air oxygen saturation was 95% with pulmonary artery pressures of 109 mm Hg systolic and 26 mm Hg diastolic (mean 55 mm Hg) and a pulmonary vascular resistance 688 dynes x sec x cm.

Case report: delayed resolution of severe pulmonary hypertension after isolated liver transplantation in a patient with cirrhosis

Pulmonary hypertension is now recognized to be a rare association of liver disease and portal hypertension. This report describes the slow resolution of symptomatic pulmonary hypertension in a 33-year-old woman with cirrhosis who underwent isolated liver transplantation. The patient survived the surgery and perioperative period without significant haemodynamic compromise. After liver transplantation, the patient was monitored with regular Doppler echocardiography. By 27 months the pulmonary hypertension had almost completely resolved. This observation is important, as it suggests that patients with severe pulmonary hypertension who survive the perioperative period may have an excellent outcome, although resolution may be slow.

Structural and pathologic changes in the lung vasculature in chronic liver disease

The hepatopulmonary syndrome results from erythrocytes bypassing the lung without oxygenation. In addition to ventilation-perfusion mismatching, the hypoxemia may result from portapulmonary shunting, passage around alveoli through pleural and hilar blood vessels, and intrapulmonary vascular dilatations. Dilated vascular channels between arteries and veins on the pleural surface are seen more often than dilated intrapulmonary capillaries in chronic liver disease. These anastomoses appear grossly as vascular "spider nevi" on the pleura. Portal vein-to-pulmonary vein anastomoses could produce arterial hypoxemia because the deoxygenated portal venous blood can mix with oxygenated pulmonary venous blood. There is an association of esophageal varices with the hepatopulmonary syndrome and anastomoses between the portal veins and pulmonary veins have been found in both animals and humans. As portal pressures increase, the mediastinal veins enlarge, enhancing the chance that they may penetrate the pleura and drain into pulmonary veins. Direct splenic injections in patients, however, suggest that this shunt pathway is uncommon and small. Pulmonary artery injection studies have demonstrated dilated intrapulmonary vascular segments in humans and animals. Dilation of capillaries may allow a more rapid flow through the lung and the greater distance between the erythrocyte and alveolar wall may make it more difficult to oxygenate rapidly passing erythrocytes. Pulmonary capillary dilation can explain the abnormalities of the perfusion lung scan and contrast echocardiogram that portapulmonary shunting cannot. Pulmonary hypertension may occur in chronic liver disease even without arterial hypoxemia, but it is rare. The prevalence of hypertensive pulmonary vascular disease in patients with cirrhosis of the liver is less than 1%, although a higher percentage (2%) has been found when patients with portal hypertension were studied by cardiac catheterization. The hypertensive pulmonary vascular disease (pulmonary arteriopathy with plexiform lesions) that occurs in patients with liver disease appears identical to that encountered in patients with congenital cardiac shunts and unexplained (primary) pulmonary hypertension.

Pulmonary hypertension in chronic liver disease

Pulmonary hypertension develops in approximately 2% of patients with portal hypertension. Diagnosis is often difficult and requires a high degree of clinical suspicion. Treatment of patients with portal and pulmonary hypertension is limited, and mean survival following diagnosis is approximately 15 months. The effect of liver transplantation on the natural history of disease is discussed.

Pulmonary endocrine cells in plexogenic pulmonary arteriopathy associated with cirrhosis

A clear association has been described between numbers of pulmonary endocrine cells and the migration and/or proliferation of myofibroblasts which is thought to underlie the vascular changes seen in plexogenic pulmonary arteriopathy due to cardiac shunts and primary pulmonary hypertension. In contrast, the pulmonary endocrine system in a subject with florid pulmonary plexogenic arteriopathy associated with cirrhosis was entirely normal, suggesting possible differences in its pathogenesis.

Pathology of pulmonary hypertension: a human and experimental study

To clarify the histopathological characteristics of pulmonary hypertension (PH) in Japan, and to clarify the role of serotonin and endothelin in monocrotaline induced PH, human histopathological studies and experimental studies were carried out. An epidemiological study based on the Annual of the Pathological Autopsy Cases in Japan, and a morphological study on autopsy cases of congenital heart disease and idiopathic PH were performed. Plasma levels of serotonin and endothelin, vascular responsiveness to serotonin, and the effects of a selective serotonin antagonist, DV-7028, were investigated after monocrotaline injection. Plexogenic pulmonary arteriopathy was prevalent, and recurrent pulmonary thromboembolism and pulmonary veno-occlusive disease extremely rare among primary pulmonary hypertension in Japan. In secondary PH, systemic lupus erythematosus and mixed connective tissue disease were frequent and showed particularly severe intimal and medial thickening. After an injection of monocrotaline, plasma serotonin and endothelin levels were raised, and pulmonary arteries showed hyperreactivity to serotonin. DV-7028 (5-HT2 receptor antagonist) attenuated the rise in pulmonary artery pressure and the various effects of monocrotaline. There may be some genetic difference between PH in Japan and other countries. Roles for serotonin and endothelin in the initiation and progression of monocrotaline induced PH are suggested.

Pulmonary hypertension associated with portal hypertension in a child with Williams syndrome--a case report

A 14-year-old white female with Williams syndrome and portal hypertension presented in shock; at autopsy she was found to have grade II to VI vascular changes of pulmonary hypertension. This case demonstrates the association of portal hypertension and pulmonary hypertension in a pediatric patient.

Association of Sjögren's syndrome with pulmonary hypertension: report of two cases and review of the literature

We report two autopsy cases of Sjögren's syndrome associated with pulmonary hypertension. The pulmonary muscular arteries of both cases showed concentric fibrocellular intimal proliferation, medial hypertrophy, and plexiform lesions. To determine the significance and pathogenesis of this rare association, we carried out morphometric and immunofluorescent studies and reviewed the seven similar cases reported in the literature. Depositions of immunoglobulin G, Clq, C3c, C4, and C5 were observed in the pulmonary arterial walls of both of our cases. Morphometric studies revealed increased medial thickness to radius ratios and intimal thickness to radius ratios of the pulmonary muscular arteries in both cases. Previously reported patients were all female, and those cases were frequently associated with Raynaud's phenomenon. This report provides additional and convincing evidence for an association of Sjögren's syndrome and plexogenic pulmonary hypertension based on a detailed study of two cases and a review of the literature. The significance and pathogenesis of this association were examined, but not clarified. However, our studies add to the accumulating data suggesting a link between autoimmune diseases and chronic pulmonary hypertension.

Pulmonary dysfunction in advanced liver disease: frequent occurrence of an abnormal diffusing capacity

PURPOSE

Abnormalities in pulmonary function have been reported in association with chronic liver disease of varied etiology. The aim of this study was to better define the frequency and nature of these abnormalities in patients who were being evaluated for liver transplantation.

PATIENTS AND METHODS

We performed a battery of pulmonary function tests and chest radiographs in 116 consecutive patients (50 men, 66 women; aged 19 to 70 years, mean 44.6 years) with severe advanced liver disease who were hospitalized specifically for evaluation for possible orthotopic liver transplantation and were able to perform technically satisfactory tests. In 17 patients, quantitative whole-body technetium-99m macroaggregated albumin perfusion scanning was also performed for assessment of possible right-to-left shunting through intrapulmonary vascular dilatations.

RESULTS

The most commonly affected test of lung function was the single-breath diffusing capacity for carbon monoxide (DLCO), which was abnormal in 48%, 45%, and 71% of patients who never smoked, former smokers, and current smokers, respectively. Ventilatory restriction was noted in 25% of all patients, airflow obstruction (reduced ratio of forced expiratory volume in 1 second to forced vital expiratory volume in 1 second to forced vital capacity) in only 3%, and a widened alveolar-arterial oxygen gradient in 45%. Diffusion impairment was accompanied by a restrictive defect in only 35% of the patients and by an abnormally widened alveolar-arterial oxygen gradient in 60%. When diffusion impairment was accompanied by an oxygenation defect, it was also associated with a significantly increased right-to-left shunt fraction (mean 24.9%) assessed from quantitative whole-body perfusion imaging. On the other hand, isolated diffusion impairment unaccompanied by significant hypoxemia (noted in approximately a third of the patients with a reduced DLCO) was not associated with evidence of significant intrapulmonary shunting (mean right-to-left shunt fraction 6.7%).

CONCLUSIONS

Most patients with advanced liver disease have one or more types of abnormality in lung function, a reduced DLCO being the single most common functional defect. Mechanisms accounting for the abnormality in gas transfer may include intrapulmonary vascular dilatations, diffuse interstitial lung disease, pulmonary vaso-occlusive disease, and/or ventilation-perfusion imbalance.

The lung in patients with cirrhosis

To summarize, nowadays it seems clear that in patients with cirrhosis: (a) the pulmonary circulation is usually markedly dilated. (b) This vasodilation is due to a loss of vascular tone and it is characterized by a poor (or even absent) vascular reactivity in front of the hypoxic stimulus. (c) This abnormal behaviour of the pulmonary circulation results in VA/Q mismatching (basically perfusion of low VA/Q units) independently of airway disease, and may lower arterial PO2. (d) In the most severe cases, shunt (and perhaps O2 diffusion limitation) is becoming progressively more important. (e) The high cardiac output and minute ventilation of these patients minimize or prevent the appearance of arterial hypoxemia at rest. (f) The fall in arterial PO2 during exercise is not due to a deterioration of the degree of VA/Q mismatching seen at rest nor to any limitation in the diffusion of oxygen. It is caused by the relative 'normalization' (with respect to the metabolic demands) of the haemodynamic and ventilatory status of the patient. This may not apply to patients with severe resting arterial hypoxemia in whom the mechanisms modulating pulmonary gas exchange during exercise have not yet been addressed. What remains to be elucidated at the present time? (a) Which is (are) the precise biochemical mediator(s) of this low pulmonary vascular tone and, presumably, failure of hypoxic pulmonary vasoconstriction? It might be either a substance(s) that the failing liver fails to produce or detoxify. Thus, the ultimate biochemical basis of these physiological abnormalities must still necessarily remain speculative while awaiting future studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Primary pulmonary hypertension. Vascular structure, morphometry, and responsiveness to vasodilator agents

The use of pharmacologic agents in the treatment of pulmonary hypertension has not proved to be uniformly successful or predictable. One possible reason for the vagaries in response is that the pulmonary vascular lesions are not consistent. We examined the relation between the structure of the pulmonary resistance vessels in unexplained (primary) pulmonary hypertension and the response to pulmonary vasodilators. Our study involved 19 patients with clinically unexplained pulmonary hypertension (mean pressure, 59 +/- 14 mm Hg). After characterizing them clinically and performing control hemodynamic measurements, we determined the acute effects of a series of vasodilator agents that have different mechanisms of action. In 16 patients, lung biopsy material was related to the hemodynamic studies; in nine patients, including six who had undergone open lung biopsy, the hemodynamic studies were related to the pathologic changes found at autopsy. Histologic specimens from all 19 patients were evaluated qualitatively and sorted into three subsets of hypertensive pulmonary arteriopathy: medial hypertrophy (with minimal intimal proliferation), arteriopathy with plexiform lesions (associated predominantly with concentric laminar intimal proliferation and fibrosis), and arteriopathy with microthrombotic lesions (associated predominantly with eccentric intimal proliferation and fibrosis). The 16 lung biopsies were also quantitated by morphometric techniques. Using a decrease in calculated pulmonary vascular resistance of more than 30% accompanied by a decrease in mean pulmonary arterial pressure of at least 10% to define vasodilation, only four patients were responders. The patients varied considerably in their responses to different vasodilator agents. Patients with similar clinical and hemodynamic profiles differed considerably with respect to the nature of their pulmonary vascular obstructive lesions and their responses to vasodilator agents. Qualitative histologic examination of lung tissue did not provide a basis for predicting how individual patients would respond to vasodilator agents. However, quantitative morphologic analysis of the initial open lung biopsy specimens did prove helpful in predicting acute responsiveness to vasodilator agents and the subsequent clinical course of these patients with unexplained (primary) pulmonary hypertension. An intimal area of more than 18% of the vascular cross-sectional area had an 85% predictive value for identifying the patients who did poorly during the first 36 months of follow-up.

Pulmonary hypertension associated with portal hypertension in childhood. Case report of a 6-year-old child and review of the literature

Pulmonary hypertension is a rare complication of portal hypertension. Reports of childhood cases especially rare. This report describes an autopsy case of a 6-year-old boy with congenital biliary atresia followed by liver cirrhosis in whom severe hypertensive pulmonary arterial changes, including medial hypertrophy, intimal fibrosis and plexiform lesions were demonstrated. Fresh and organizing fibrin-platelet thrombi as well as probable organized thrombi with recanalization were occasionally found in the pulmonary vasculature, but it was thought that they had probably been formed locally as a late complication rather than being of thromboembolic origin. Retrospectively, the chest roentgenograms had revealed abnormalities suggestive of pulmonary hypertension since infancy, but the patient showed no apparent symptoms of it during life. Previously reported childhood cases of pulmonary hypertension associated with portal hypertension were briefly reviewed. Although the mechanism is presently not known, it is suggested that patients with portal hypertension, even in early childhood, are at risk of developing this unusual complication.

Pulmonary aspects of chronic liver disease and liver transplantation

A vast spectrum of pulmonary pathologic conditions occurs in association with chronic liver diseases, and clinically important manifestations, such as arterial hypoxemia, can result. Both pulmonary vascular and parenchymal abnormalities can contribute to the dysfunction, as evidenced by results of pulmonary function tests and gas exchange studies. The clinical implications of identifying such pulmonary problems range from alleviation of symptoms, especially dyspnea, to comprehensive assessment of patients before and after liver transplantation. Physicians should be aware of these potential pulmonary disorders that can complicate liver disease and liver transplantation so that management of affected patients can be improved.