Ventilation-perfusion relationships and central haemodynamics in patients with cirrhosis. Effects of a somatostatin analogue

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.

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.

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.

Current concepts in the management of hepatopulmonary syndrome

The hepatopulmonary syndrome is characterized as the triad of liver disease, pulmonary gas exchange abnormalities leading to arterial deoxygenation and evidence of intrapulmonary vascular dilatations. This review summarizes the pathological mechanisms leading to pulmonary vascular changes in hepatopulmonary syndrome. The role of the three currently used diagnostic imaging modalities of contrast-enhanced echocardiography, perfusion lung scanning and pulmonary arteriography that identify the presence of intrapulmonary vascular abnormalities are reviewed. Liver transplantation is considered to be the definitive treatment of hepatopulmonary syndrome with often successful reversal of hypoxemia, however other treatments have been trialed. This review further appraises the evidence for the use of pharmacological agents and the role of radiological interventions in hepatopulmonary syndrome.

Effect of oral garlic on arterial oxygen pressure in children with hepatopulmonary syndrome

AIM: To study the effect of oral garlic on arterial oxygen pressure in children with hepatopulmonary syndrome.

METHODS: Garlic powder in a capsule form was given to 15 children with hepatopulmonary syndrome (confirmed by contrast echocardiography) at the dosage of 1 g/1.73 m² per day. Patients were evaluated clinically and by arterial blood gas every four weeks.

RESULTS: The garlic capsule was administered to 15 patients with hepatopulmonary syndrome. There were 10 boys and 5 girls with a mean age of 9.4 ± 3.9 years. The underlying problems were biliary tract atresia (4 patients), autoimmune hepatitis (4 patients), cryptogenic cirrhosis (4 patients) and presinusoidal portal hypertension (3 patients). Eight patients (53.3%) showed an increase of 10 mmHg in their mean arterial oxygen pressure. The baseline PaO₂ was 65.6 ± 12.1 mmHg in the responder group and 47.1 ± 11.2 mmHg in non-responder group. At the end of treatment the mean PaO₂ in responders and non-responders was 92.2 ± 7.75 mmHg and 47.5 ± 11.87 mmHg, respectively (P < 0.01).

CONCLUSION: Garlic may increase oxygenation and improve dyspnea in children with hepatopulmonary syndrome.

Recent advances in hepatopulmonary syndrome

Hepatopulmonary syndrome is defined as the clinical triad of advanced liver disease, arterial deoxygenation and intrapulmonary vascular dilatation. Its pathogenesis is not completely understood. Excessive pulmonary nitric oxide production seems to be one of the factors that contribute to the intrapulmonary vascular dilatation. Other mediators such as endothelin-1 and the heme oxygenase-1/carbon monoxide system have recently been found to be important contributors. The major clinical manifestations are arterial hypoxemia, clubbed fingers and spider nevi. Orthodeoxia is the characteristic clinical feature. Contrast-enhanced echocardiography is the preferred screening test. 99mTechnetium macroaggregated albumin (Tc-99m MAA) lung perfusion scan can further specify the diagnosis of hepatopulmonary syndrome and quantify the magnitude of shunting. No clearly effective medical treatments have been found. Although liver transplantation seems feasible to reverse this situation, it is associated with increased postoperative morbidity and mortality. A preoperative arterial oxygen tension of 50 mmHg or less and Tc-99m MAA shunt fractions of 20% or more are strong predictors of postoperative mortality that can be used to stratify patients with better outcome.

Detection of early central circulatory transits in patients with cirrhosis by gamma variate fit of indicator dilution profiles

Patients with cirrhosis have hyperdynamic circulation with abnormally distributed blood volume and widespread arteriovenous communications. We aimed to detect possible very early (i.e., before 4 s) and early (i.e., after 4 s) central circulatory transits and their potential influence on determination of central and arterial blood volume (CBV). Thirty-six cirrhotic patients and nineteen controls without liver disease undergoing hemodynamic catheterization were given central bolus injections of albumin with different labels. Exponential and gamma variate fits were applied to the indicator dilution curves, and the relations between flow, circulation times, and volumes were established according to kinetic principles. No significant very early central circulatory transits were identified. In contrast, early (i.e., 4 s to maximal) transits corresponding to a mean of 5.1% (vs. 0.8% in controls; P < 0.005) of cardiac output (equivalent to 0.36 vs. 0.05 l/min; P < 0.01) were found in cirrhotic patients. These early transits averaged 7.7 vs. 12.7 and 17.2 s of ordinary central transits of cirrhotic patients and controls, respectively (P < 0.001). Early transits were directly correlated to the alveolar-arterial oxygen difference in the cirrhotic patients (r = 0.46, P < 0.01) but not in controls (r = 0.04; not significant). There was good agreement between the CBV determined by the conventional indicator dilution method and that determined by separation of early and ordinary transits by the gamma variate fit method (1.51 vs. 1.53 liter; not significant). In conclusion, no very early central circulatory transits were identified in cirrhotic patients. A significant part of the cardiac output undergoes an early transit, probably through pulmonary shunts or areas with low ventilation-perfusion ratios in cirrhotic patients. Composite determination of CBV by the gamma variate fit method is in close agreement with established kinetic methods. The study provides further evidence of abnormal central circulation in cirrhosis.

Octreotide-induced hypoxemia and pulmonary hypertension in premature neonates

The authors report 2 cases of premature neonates who had enterocutaneous fistula complicating necrotizing enterocolitis. Pulmonary hypertension developed after administration of a somatostatin analogue, octreotide, to enhance resolution of the fistula. The authors discuss the mechanism of the occurrence of this complication and recommend caution of its use in high-risk premature neonates.

Blood volume distribution in patients with cirrhosis: aspects of the dual-head gamma-camera technique

BACKGROUND/AIMS

Patients with cirrhosis have increased total blood volume (TBV). The size of the "effective" blood volume has been closely investigated, whereas the distribution of the blood volume outside the thorax has not been examined. The aim was to estimate the blood volume distribution in patients with cirrhosis and portal hypertension, using a dual-head gamma-camera technique (DHGCT) and to validate this technique.

METHODS

Twenty-three patients with cirrhosis, 11 non-cirrhotic control patients, and six healthy controls had their blood volume distribution determined by the DHGCT.

RESULTS

The close relation between the estimated blood volume in the thorax region and the central and arterial blood volume, obtained by the dynamic indicator dilution technique (r=0.87, P<0.001), indicates validity of the DHGCT. Whole-body scintigraphy showed altered blood volume distribution in the cirrhotic patients with increased splanchnic blood volume (SpBV: 25.0 vs. 18.2% of TBV in controls, P<0.001), and all but one patient with hepatic venous pressure gradient above 12 mmHg had SpBV above 20% of TBV, but the blood volumes in the liver region were similar.

CONCLUSIONS

DHGCT is a valid method of estimating the blood volume distribution. Patients with cirrhosis and portal hypertension have grossly increased blood pooling in the splanchnic region, indicating splanchnic congestion.

Novel presentation and approach to management of hepatopulmonary syndrome with use of antimicrobial agents

A 44-year-old man with hepatitis C-associated liver cirrhosis, cyanosis, digital clubbing, and platypnea presented with left-side hemiplegia found to be due to a brain abscess. Hepatopulmonary syndrome was diagnosed after demonstration of the presence of a massive intrapulmonary shunt. Although the anomalous vascular channel never was defined anatomically, follow-up studies confirmed the presence of a functional shunt. Culture of a sample from the abscess yielded Streptococcus intermedius. It was hypothesized that the patient's pulmonary vascular pathology was due, in large part, to chronic elevated levels of nitric oxide (a potent vasodilator thought to be generated by endotoxin absorbed from the gut). Treatment with oral norfloxacin was initiated on the basis of data that this antibiotic reduces endotoxemia and concomitant nitric oxide production in patients with cirrhosis. Four months after initiation of treatment, the patient's hypoxia had resolved.

The hepatopulmonary syndrome

The hepatopulmonary syndrome is a triad of liver disease, increased alveolar-arterial oxygen gradient and intrapulmonary vascular dilatations. Manifestations include orthodeoxia, platypnoea and hyperdynamic circulation. Intrapulmonary vascular abnormalities, perhaps mediated by nitric oxide, cause hypoxaemia by shunting, a perfusion-diffusion defect, and ventilation-perfusion mismatching. Contrast-enhanced echocardiography is the method of choice for demonstrating pulmonary vascular abnormalities, although perfusion lung scanning is a more specific and sensitive test. Angiography is best reserved for patients with poor response to 100% oxygen and defines whether vascular dilatations are of the diffuse 'spongy' type or, less commonly, discrete arteriovenous communications amenable to embolization. About 80% of patients with the hepatopulmonary syndrome eventually have improved oxygenation after liver transplantation, thereby making worsening hypoxaemia the primary indication for transplantation in many instances. Nevertheless, severe hypoxaemia carries a peri-operative mortality of 30% and reliable predictors of successful outcome after transplantation remain to be determined.

Cardiopulmonary dysfunction in cirrhosis

Cirrhosis is associated with several circulatory abnormalities. These include hyperkinetic systemic and splanchnic circulation, hepatopulmonary syndromes including pulmonary hypertension, and cirrhotic cardiomyopathy. Hepatopulmonary syndrome generally refers to hypoxaemia seen in patients with chronic liver disease and appears to be relatively common, although often subclinical. However, significant pulmonary hypertension occurs in 0.2-0.7% of cirrhotic patients. Nitric oxide and/or other vasodilators appear to be involved in the pathogenesis of hepatopulmonary syndrome through induction of pulmonary capillary dilatation which increases the alveolar-arterial oxygen gradient. Cirrhotic cardiomyopathy refers to abnormal left ventricular function which is manifested under conditions of physiological or pharmacological stress. The emergence of liver transplantation as an effective treatment for end-stage liver disease has led to recognition of previously subclinical cardiomyopathy and congestive heart failure accounts for significant morbidity and mortality after this procedure. Diminished myocardial beta-adrenergic receptor function has been shown to play an important role in the pathogenesis of this condition. The contributions of other factors including nitric oxide, catecholamines and membrane fluidity changes are under investigation. Cirrhotic patients also have an increased incidence of other cardiac abnormalities, such as endocarditis and pericardial effusions.

Effects of octreotide on central hemodynamics and systemic oxygen use in patients with viral cirrhosis

OBJECTIVE

Octreotide has potentially beneficial effects in patients with cirrhosis. However, the effects of octreotide on central hemodynamics and oxygen use have not been established. The present study was undertaken to evaluate the effect of octreotide on central hemodynamics and oxygen use in patients with viral cirrhosis.

METHODS

Twenty-five patients with cirrhosis were enrolled in the study. They were randomly assigned to receive either placebo (n = 10) or a continuous infusion of 100 microg/h of octreotide after an initial 100-microg bolus (n = 15). Hemodynamic measurements and oxygenation values were obtained before and 60 min after octreotide or placebo administration.

RESULTS

Placebo administration did not have any effect on hemodynamic and oxygenation values. In patients who received octreotide, systemic hemodynamic values including cardiac index, mean arterial pressure, and systemic vascular resistance were not affected. The mean pulmonary arterial pressure tended to increase after octreotide administration but was statistically insignificant. There was a significant increase in pulmonary arterial vascular resistance, whereas the pulmonary capillary wedge pressure and right atrial pressure were significantly decreased. Arterial oxygen tension, systemic oxygen uptake, and oxygen extraction ratio were significantly decreased after octreotide administration, whereas oxygen transport as well as arterial and mixed venous oxygen contents remained unchanged.

CONCLUSIONS

In patients with viral cirrhosis, octreotide administration exerted a significant effect on pulmonary circulation. It also resulted in a decrease in systemic oxygen uptake and oxygen extraction ratio. These results suggested that octreotide may impair tissue oxygenation in patients with viral cirrhosis.

The hepatopulmonary syndrome

The hepatopulmonary syndrome is a disease entity seen in association with liver failure and other disease entities. It is a devastating consequence of liver failure that results in a significant morbidity for affected patients. Currently, there are no identified medications that ameliorate the symptoms of hypoxemia in this disease state. Recent research, however, has begun to unravel the pathobiology of the vascular dilations that arise in the lungs of patients with liver failure. In this article, a compendium of current knowledge is presented, as well as the contemporary methods for identifying and treating patients.

Endogenous nitric oxide in exhaled air from patients with liver cirrhosis

BACKGROUND

The aim of this study was to investigate the potential effects of liver insufficiency on nitric oxide concentrations in exhaled air.

METHODS

Nitric oxide concentrations in the exhaled air from 13 patients with liver cirrhosis and 11 healthy control subjects was examined by the single-breath technique.

RESULTS

There was a clear correlation between Child-Pugh score and NO in exhaled air (peak after 15 sec of breathholding, R = 0.623, P = 0.023). Similarly, there were significant correlations in peak NO concentrations and alkaline phosphatase, bilirubin, aspartate and alanine aminotransferase, and albumin. The most severely ill patient in our study had the highest NO concentrations in her exhaled air. On recovery from her liver illness the concentration of NO in her exhaled air decreased. There was no correlation between circulating levels of the endogenous NO synthase inhibitors asymmetric and symmetric N(G), N(G)-dimethyl-arginine and exhaled NO concentrations.

CONCLUSIONS

The present data show a correlation between endogenous NO formation in the respiratory system and liver dysfunction. This might contribute to the understanding of the pathophysiology in pulmonary vasodilatation in liver disease.

Effect of octreotide on systemic, central, and splanchnic haemodynamics in cirrhosis

BACKGROUND/AIMS

Cirrhosis with portal hypertension is associated with changes in the splanchnic and systemic haemodynamics, and subsequent complications, such as bleeding from oesophageal varices, have led to the introduction of long-acting somatostatin analogues in the treatment of portal hypertension. However, reports on the splanchnic and systemic effects of octreotide are contradictory and therefore the aim of the present study was to assess the effects of continuous infusion of octreotide on central and systemic haemodynamics, portal pressures, and hepatic blood flow.

METHODS

Thirteen patients with cirrhosis underwent liver vein catheterisation. Portal and arterial blood pressures were determined at baseline and 10, 30, and 50 min after a bolus injection of octreotide 100 micrograms, followed by continuous infusion of octreotide 100 micrograms/ h for 1 h. Hepatic blood flow, cardiac output, central and arterial blood volume, and central circulation time were determined at baseline and 50 min after the start of the octreotide infusion.

RESULTS

The mean arterial blood pressure increased during the first 10 min (p < 0.0005), but returned to baseline after 50 min. The central and arterial blood volume (-16%, p < 0.005) and the central circulation time (-8%, p < 0.05) were significantly decreased after 50 min, whereas the cardiac output did not change significantly. The hepatic venous pressure gradient and the hepatic blood flow did not change significantly at any time after infusion of octreotide.

CONCLUSIONS

Octreotide does not affect the portal pressure or hepatic blood flow, whereas it may further contract the central blood volume and thereby exert a potentially harmful effect on central hypovolaemia in patients with cirrhosis. However, these early effects do not exclude the possibility that administration of longacting somatostatin analogues over a longer period may have a beneficial effect.

Platelet basal cytosolic calcium: the influence of plasma factors in cirrhosis

BACKGROUND

Platelet cytosolic calcium is necessary for normal platelet function, and may reflect intracellular signalling in vascular smooth muscle cells.

METHODS

The cytosolic calcium of platelets from patients with cirrhosis and control subjects was measured in contact with plasma from either source, using FURA 2AM.

RESULTS

The basal cytosolic calcium of patients with cirrhosis was found to be significantly lower than that of control subjects (95.7 +/- 10.0 cf. 128.0 +/- 7.8 nmol/l; p = 0.02). When platelets from control subjects were incubated for 45 min with freshly obtained plasma from patients with cirrhosis, the control platelet cytosolic calcium fell to concentrations similar to those of patient platelets (93.0 +/- 7.8 nmol/l; p < 0.005). Such an effect was not observed if patient serum or plasma that had previously been frozen was used. When patient platelets were incubated with fresh control subject plasma, the platelet cytosolic calcium increased (165.4 +/- 19.9 nmol/l; p = 0.01).

CONCLUSION

These results indicate that a plasma-borne factor, sensitive to freezing, is responsible for the abnormalities of platelet calcium signalling noted in cirrhosis.

Effect of oxygen inhalation on systemic, central, and splanchnic haemodynamics in cirrhosis

BACKGROUND/AIMS

Patients with cirrhosis exhibit a hyperdynamic circulation with increased cardiac output and low arterial blood pressure. The aim of the present study was to assess the effects of oxygen inhalation on systemic, central, and splanchnic haemodynamics and vasoactive systems in patients with cirrhosis (n = 19).

RESULTS

Spirometry was normal, but the carbon monoxide diffusing capacity (transfer factor) was significantly decreased, 18.8 ml.min-1.mmHg-1 (-32% of that predicted, p < 0.0001), and correlated significantly with the cardiac output (r = 0.78, p < 0.0005), plasma volume (r = 0.72, p < 0.001) and the central and arterial blood volume (r = 0.67, p < 0.005). After inhalation of 100% oxygen over a period of 20 min, the cardiac output decreased from 7.4 to 6.6 l/min (p < 0.0005), and the systemic vascular resistance increased from 980 to 1124 dyn.s.cm-5 (p < 0.005). The change in systemic vascular resistance was significantly greater in patients with mild liver dysfunction than in those with severe liver dysfunction (p < 0.02). In contrast, no significant changes were seen in the arterial or portal venous pressures during inhalation of oxygen. Arterial concentrations of catecholamines, renin, endothelin-1, and calcitonin gene-related peptide were all increased in patients with cirrhosis, but only the catecholamine concentrations decreased significantly (noradrenaline -13%, p < 0.02 and adrenaline -16%, p < 0.01) in response to oxygen.

CONCLUSION

During oxygen inhalation cardiac output decreases and systemic vascular resistance increases in association with a decrease in arterial concentrations of catecholamine, but oxygen supply in patients with cirrhosis does not normalise the hyperdynamic circulation or the low arterial blood pressure.

Hepatopulmonary syndrome. A pulmonary vascular complication of liver disease

Hepatopulmonary syndrome is part of the spectrum of pulmonary vascular disorders seen in advanced liver disease. The pathophysiology of these entities likely is dependent on the degree of pulmonary vasoconstriction or vasodilation that occurs. Our understanding of hepatopulmonary syndrome has helped further our knowledge of the interaction of the liver and the lung. Advances in the management of this disorder, especially liver transplantation, finally have allowed us to offer some hope to patients with this disease.