Prognostic significance of the hepatopulmonary syndrome in patients with cirrhosis

Hepatopulmonary syndrome increases the postoperative mortality rate following liver transplantation: a prospective study in 90 patients

Hepatopulmonary syndrome (HPS) is a frequent pulmonary complication of patients with end-stage liver diseases. HPS is diagnosed by hypoxemia and pulmonary vascular dilatation and is an independent risk factor of mortality. Orthotopic liver transplantation (OLT) is the only factor that modifies the natural course of HPS. Once patients with HPS have been transplanted, their long-term survival rate is similar to transplanted patients without HPS. Consequently, HPS is an indication of OLT whatever the severity of hypoxemia. However, besides the favorable long-term survival of HPS patients with OLT, a high postoperative mortality (mostly within 6 months) has been suggested. The aim of our study was to analyze the incidence of HPS and postoperative outcome after OLT in 90 consecutive patients. All patients were prospectively included and had blood gas analysis to detect HPS. Patients with hypoxemia had contrast echocardiography to confirm HPS. Nine patients had HPS with a 50 </= PaO(2)</= 70 mmHg. Among them 3 (33%) died while the mortality rate was 9.2% in the group without HPS (7 over 76 patients). In the HPS patients who survived, the syndrome completely recovered within 6 months. In conclusion, our study shows a high postoperative mortality rate following OLT even though the preoperative PaO(2) was >50 mmHg in all HPS patients transplanted.

Outpatient Management of Cirrhosis: A Narrative Review

Cirrhosis is the 12th leading cause of death in the United States. Individuals with cirrhosis are at risk for many potential complications. Complications can be managed or detected early with proper outpatient management. The most lethal of these complications is bleeding esophageal varices. All patients with cirrhosis should be screened for the presence of varices and treated when indicated. The most common complication seen in these patients is ascites. Ascites can be treated with dietary modifications and a diuretic regimen. Other potential complications include spontaneous bacterial peritonitis, hepatocellular carcinoma, hepatic encephalopathy, hepatorenal syndrome, and hepatopulmonary syndrome. The outpatient management of these complications will be discussed in this paper, along with the use of vaccinations, educating patients about the avoidance of hepatotoxic drugs, and when to refer a patient for liver transplant.

Hepatopulmonary syndrome

The hepatopulmonary syndrome (HPS) is an important and often under-recognized vascular complication of cirrhosis and portal hypertension characterized by pulmonary vascular dilatation, which results in hypoxemia. This syndrome is identified in as many as 20% of patients who are evaluated for orthotopic liver transplantation (OLT), and it has recently been found to increase mortality in affected patients, particularly when hypoxemia is severe. Currently, OLT is the only therapy established to reverse intrapulmonary vasodilatation, although postoperative mortality is increased in patients with severe hypoxemia. No randomized controlled trials of pharmacologic therapies have been undertaken, but supplemental oxygen improves oxygenation. Data derived from case reports, small studies, and experimental models suggest that pharmacologic therapies may be effective. In cirrhotic patients with HPS, particularly those with moderate hypoxemia (PaO2 < 60 mmHg), OLT should be considered prior to the development of severe deoxygenation. Supplemental oxygen should be given to patients with a PaO2 < 60 mmHg or those with exercise oxygen desaturation. For those patients with mild hypoxemia or those who are not OLT candidates, a trial of pharmacologic treatment may be considered.

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.

Hepatopulmonary syndrome in patients with chronic liver disease: role of pulse oximetry

Background

Hepatopulmonary syndrome (HPS) is a rare complication of liver diseases of different etiologies and may indicate a poor prognosis. Therefore, a simple non-invasive screening method to detect HPS would be highly desirable. In this study pulse oximetry was evaluated to identify patients with HPS.

Methods

In 316 consecutive patients with liver cirrhosis (n = 245), chronic hepatitis (n = 69) or non-cirrhotic portal hypertension (n = 2) arterial oxygen saturation (SaO₂) was determined using a pulse oximeter. In patients with SaO₂ ≤92% in supine position and/or a decrease of ≥4% after change from supine to upright position further diagnostic procedures were performed, including contrast-enhanced echocardiography and perfusion lung scan.

Results

Seventeen patients (5.4%) had a pathological SaO₂. Four patients (1.3%) had HPS. HPS patients had a significant lower mean SaO₂ in supine (89.7%, SD 5.4 vs. 96.0%, SD 2.3; p = 0.003) and upright position (84.3%, SD 5.0 vs. 96.0%, SD 2.4; p = 0.001) and had a lower mean PaO₂ (56.2 mm Hg, SD 15.2 vs. 71.2 mm Hg, SD 20.2; p = 0.02) as compared to patients without HPS. The mean ΔSaO₂ (difference between supine and upright position) was 5.50 (SD 7) in HPS patients compared to non-HPS patients who showed no change (p = 0.001). There was a strong correlation between shunt volume and the SaO₂ values (R = -0.94).

Conclusion

Arterial SaO₂ determination in supine and upright position is a useful non-invasive screening test for HPS and correlates well with the intrapulmonary shunt volume.

The Importance of Predicting the Prognosis in Patients With Hepatopulmonary Syndrome: A Simple Scoring System

Hepatopulmonary syndrome (HPS) is a pulmonary vascular disorder, complicating hepatic diseases, and is responsible for an increased morbidity and mortality among patients awaiting liver transplantation. Nowadays, it is recognized as an independent risk factor for death in this patient population. The severity of hypoxemia and the advanced stage of the liver dysfunction are determinants for the prognosis. Therefore, the possibility to be successful, thus improving survival, consists of addressing HPS at an earlier stage, giving more attention to moderate evidences of this pathology instead of the severe ones. On the basis of scientific evidence, we suggest a simple scoring system to predict prognosis among patients with HPS, founded on the integration of two main factors: the severity of hepatic disease, expressed as class of Child-Pugh, and the severity of the hypoxemia. This model of prognostic evaluation has the objective of estimating the additional risk of these patients, thereby avoiding a deleterious underestimate of risk and an arbitrariness of management.

Significance of Hypoxemia Screening in Candidates for Liver Transplantation: Our Experience

Hepatopulmonary syndrome (HPS) is recognized as one of the causes of hypoxemia in patients with chronic liver disease. This complication is responsible for increased mortality and increased perioperative risk in liver transplantation candidates. Recent data from the literature suggest extending the screening for HPS to all candidates for liver transplantation. The aim of this retrospective study was to evaluate the incidence of hypoxemia among a population of patients awaiting liver transplantation. Using pulse oximetry as a screening tool for hypoxemia, 39 of 198 patients (20%) were hypoxemic. The results of this study confirmed the importance of screening for hypoxemia among patients awaiting liver transplantation. In these patients, a more accurate evaluation of respiratory function should be performed to confirm or exclude the diagnosis of HPS.

Clinical features of hepatopulmonary syndrome in cirrhotic patients

AIM: To evaluate the frequency, clinical and paraclinical features of hepatopulmonary syndrome (HPS) and to determine their predictive values in diagnosis of this syndrome in patients in Iran.

METHODS: Fifty four cirrhotic patients underwent contrast enhanced echocardiography to detect intrapulmonary and intracardiac shunts by two cardiologists. Arterial blood oxygen, O₂ gradient (A-a) and orthodoxy were measured by arterial blood gas (ABG) test. The patients positive for diagnostic criteria of HPS were defined as clinical HPS cases and those manifesting the intrapulmonary arterial dilation but no other criteria (arterial blood hypoxemia) were defined as lHPS cases. HPS frequency, sensitivity, positive and negative predictive values of clinical and paraclinical features were studied.

RESULTS: Ten (18.5%) and seven (13%) cases had clinical and subclinical HPS, respectively. The most common etiology was hepatitis B. Dyspnea (100%) and cyanosis (90%) were the most prevalent clinical features. Dyspnea and clubbing were the most sensitive and specific clinical features respectively. No significant relationship was found between HPS and splenomegaly, ascites, edema, jaundice, oliguria, and collateral veins. HPS was more prevalent in hepatitis B. PaO₂< 70 and arterial-alveolar gradient had the highest sensitivity in HPS patients. Orthodoxy specificity was 100%.

CONCLUSION: Clubbing with positive predictive value (PPV) of 75% and dyspnea with negative predictive value (NPV) of 75% are the best clinical factors in diagnosis of HPS syndrome. PaO₂< 70 and P (A-a) O₂> 30 and their sum, are the most valuable negative and positive predictive values in HPS patients.

The pulmonary involvement in portal hypertension: portopulmonary hypertension and hepatopulmonary syndrome

Pulmonary abnormalities are common in patients with advanced chronic liver disease. Two distinct syndromes strictly related to the presence of portal hypertension, but clearly different from a pathophysiologic point of view, have been identified. Portopulmonary hypertension, characterized by an increased pulmonary arterial pressure, is due to a progressive arteriolar vasoconstriction induced by excess local production of vasoconstrictor substances. Hepatopulmonary syndrome results from intrapulmonary microvascular dilation caused by an inadequate synthesis or metabolism of putative pulmonary vasoactive substances leading to a functional vasodilation of the pulmonary vasculature, ultimately leading to hypoxemia. Controversies on pathogenesis imply different tentative therapeutic approaches for the medical management of these conditions. The development of portopulmonary hypertension or the hepatopulmonary syndrome has important clinical and prognostic implications facing the impact of new therapeutic strategies for the management of the main complications of advanced liver diseases on cardiopulmonary function.

Prevalence and prognosis of intrapulmonary shunts in patients with hepatic cirrhosis

We investigated the prevalence of intrapulmonary shunts in 82 patients with hepatic cirrhosis referred for echocardiography as part of liver transplantation evaluation. Intrapulmonary shunts were present in 49 of 82 patients (60%). Baseline characteristics were similar in patients with and without intrapulmonary shunts. Mean follow up was 41 +/- 15 months in patients with intrapulmonary shunts and 42 +/- 15 months in patients without intrapulmonary shunts (P not significant). At follow up, 8 of 49 patients (16%) with intrapulmonary shunts and 4 of 33 patients (12%) without intrapulmonary shunts had died (P not significant).

Liver transplantation in high-risk patients: hepatopulmonary syndrome and portopulmonary hypertension

Two pulmonary vascular disorders, considered mutually exclusive, may be present in candidates for orthotopic liver transplantation (OLT). On the one hand, hepatopulmonary syndrome (HPS), with a prevalence about 20% in end-stage liver disease, is characterized by pulmonary vascular dilatation and abnormal gas exchange. On the other hand, portopulmonary hypertension (POPH), a process defined by pulmonary hypertension associated with portal hypertension, is less common than HPS (4%). These entities have very distinct clinical implications; whereas HPS is clinically characterized by respiratory symptoms that evolve to severe hypoxemia, patients with POPH are commonly asymptomatic, frequently diagnosed in the setting of OLT, and the symptoms appear when there is hemodynamic compromise. The pathogenesis of both entities is a putative mechanism, the imbalance of vasoactive substances in pulmonary vessels. The role of OLT to reverse these vascular disorders is controversial, although complete resolution of HPS and, less frequently, POPH following OLT has been reported. The recognition that the presence of both HPS and POPH is an important cause of morbidity and mortality among recipients of OLT has resulted in a change in the policy to select OLT candidates. Accurate identification of patients with pulmonary vascular disorders associated with liver disease should be the first step in the management of OLT candidates. Because the determinants of the prognosis of OLT in the setting of these pulmonary vascular changes have not been well established, an accurate cardiopulmonary evaluation with careful assessment of pulmonary gas exchange (in HPS) and right ventricular function (in POPH) of potential OLT recipients is mandatory before the procedure.

Clinical predictors and characteristics of patients with chronic liver disease and intrapulmonary shunts

BACKGROUND

Intrapulmonary shunting (IPS) is a well-described phenomenon in chronic liver disease but its significance is not known.

HYPOTHESIS

The study was undertaken to enhance our understanding of the characteristics and prevalence of IPS.

METHODS

We retrospectively studied 204 consecutive patients with end-stage chronic liver disease who underwent a dobutamine stress echocardiogram, along with a saline contrast bubble study, as part of their pretransplant evaluation.

RESULTS

Intrapulmonary shunting of any degree was present in 56.4% of patients. Patients with IPS were more likely to report alcohol use and less likely to have diabetes mellitus. Patients in Child-Pugh classification C were more likely to have IPS than those with classification A or B. The resting room air PaO2 levels were significantly lower in patients with grade 3-4 IPS than in those with grade 1-2. Elevated estimated pulmonary systolic pressure on echocardiography was more prevalent in patients with than in those without IPS.

CONCLUSIONS

A majority of patients with end-stage chronic liver disease undergoing transplant evaluation have IPS. There are important baseline differences between patients with and without IPS. The presence of IPS is associated with increased severity of chronic liver disease. Further study is required to define the prognostic significance of IPS and its impact on future liver transplantation.

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.

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.

Natural history of hepatopulmonary syndrome: Impact of liver transplantation

Few data exist concerning survival after the diagnosis of hepatopulmonary syndrome (HPS). Although orthotopic liver transplantation (OLT) frequently results in complete resolution of HPS, the relationship between transplantation and survival has not been described. The study rationale was to describe long-term survival in patients with HPS. Data were derived from patients diagnosed with HPS at Mayo Clinic (n = 61) between 1985 and 2002, including those undergoing OLT (n = 24) and those who did not (n = 37). A case-control, Kaplan-Meier survival analysis between HPS patients and 77 patients without HPS matched for liver disease cause, model for end-stage liver disease (MELD), severity of liver disease by the Child classification, and age was described for OLT and non-OLT groups. Patients with HPS had a mean partial pressure of arterial oxygen (PaO(2)) decline of 5.2 + 2.3 mm Hg per year awaiting OLT. For HPS patients, despite similar baseline PaO(2), brain uptake of technetium macroaggregated albumin ((99m)TcMAA), or measures of hepatic dysfunction, 5-year survival associated with OLT was 76% versus 23% who did not undergo transplantation (P < .0001). Comparing those who did not undergo transplantation, HPS patients had worse 5-year survival than matched controls (P = .0003). However, reasons to deny OLT (comorbidity) in the setting of HPS may well have contributed to observed survival differences. Baseline PaO(2) </=50 mm Hg was associated with worse survival irrespective of the decision to perform OLT. In conclusion, hypoxemia of HPS is frequently progressive. As OLT outcome relates to pretransplantation PaO(2), additional MELD points should advance the priority for OLT in HPS.

[Hepatopulmonary syndrome: relationship with liver dysfunction and systemic hemodynamic disorder]

BACKGROUND AND OBJECTIVE

The hepatopulmonary syndrome (HPS) causes an increased alveolar to arterial gradient of oxygen and in advanced phases hypoxemia, as the result of pulmonary vasodilation. In liver cirrhosis, it has been demonstrated the existence of splachnic vasodilation and also in other vascular beds. Our main objectives were to know the hemodynamic status, the renal function and the condition of some humoral systems in patient diagnosed of HPS.

PATIENTS AND METHOD

We studied consecutively 32 cirrhotic patients Divided in two groups, a group of 18 cirrhotic patients with normal gaseous exchange (NGE), and another group of 14 cirrhotic patients diagnosed of HPS by contrast-enhanced transthoracic echocardiography and/or lung and brain scintigraphy with 99Tc albumin macroaggregates. They were all in rest in bed, upon alcohol and tobacco abstinence and on a diet of 50 mEq of sodium. Cardiovascular drugs were all withheld during 4 days in order to reach steady state.

RESULTS

Patients of the HPS group were characterized by a more advanced index of Child-Pugh and presence of clubbing and vascular spiders. They presented a greater degree of hypoxemia in a sitting position, greater hypocapnia and smaller transference factor values (TLCO). They also showed a hyperkinetic circulatory condition characterized by smaller arterial blood pressure, greater cardiac index, smaller vascular resistances and greater femoral flows, with smaller clearance of creatinine, elimination of urinary sodium, urinary volume/24 h and an increased plasmatic volume, accompanied with a greater activation of the renin-angiotensin-aldosterone axis and a greater urinary elimination of nitrites and nitrates.

CONCLUSIONS

The pulmonary vasodilation that explains the HPS is a constitutive part of the systemic vasodilation occurring in liver cirrhosis, and it is related to the degree of liver dysfunction as measured by the classification of Child-Pugh. The greater activation of the renin-aldosterone system and the rise of the plasmatic volume express a highest grade of arterial underfilling caused by an increment in the nitric oxide production.

Carboxyhemoglobin levels in cirrhotic patients with and without hepatopulmonary syndrome

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

GOALS

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

BACKGROUND

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

STUDY

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

RESULTS

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

CONCLUSIONS

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

Cardiac morbidity and mortality related to orthotopic liver transplantation

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

Isoflurane pretreatment lowers portal venous resistance by increasing hepatic heme oxygenase activity in the rat liver in vivo

BACKGROUND/AIMS

The heme oxygenase (HO) system contributes to the maintenance of hepatic perfusion and integrity. It was the objective of this study to determine the influence of isoflurane (ISO) on hepatic HO-1 induction and its impact on hepatic hemodynamics.

METHODS

Rats were pretreated with or without ISO for 5h. After hemodynamic measurements by pressure-, laser doppler-, and ultrasound based techniques, the liver was harvested. HO-1 was analyzed by an HO activity assay, Northern- and Western blotting.

RESULTS

ISO pretreatment induced hepatic HO-1 mRNA and protein resulting in an increase of HO activity. No effect on hsp-27, hsp-70 and hsp-90 mRNA could be observed. ISO lowered portal resistance. HO inhibition by tin protoporphyrine IX increased portal resistance in ISO pretreated animals up to control levels. This was associated with an increase in portal pressure and a reduction of portal flow. Microvascular flux was also impaired after HO blockade and ISO. However, hepatic arterial and systemic hemodynamics remained unchanged, indicating a specific effect within the portal vascular bed.

CONCLUSIONS

ISO pretreatment induces hepatic HO-1 mRNA and protein followed by an increase in HO activity, thereby reducing portal resistance. These findings indicate a beneficial effect of ISO on hepatic hemodynamics in vivo.

Hypoxic pulmonary hypertension is prevented in rats with common bile duct ligation

Biliary cirrhosis in the rat triggers intrapulmonary vasodilatation and gas-exchange abnormalities that characterize the hepatopulmonary syndrome. This vasodilatation correlates with increased levels of pulmonary microcirculatory endothelial NO synthase (eNOS) and hepatic and plasma endothelin-1 (ET-1). Importantly, during cirrhosis, the pulmonary vascular responses to acute hypoxia are blunted. The purpose of this work was to examine the pulmonary vascular responses and adaptations to the combination of liver cirrhosis and chronic hypoxia (CH). In addition to hemodynamic measurements, we investigated whether pulmonary expression changes of eNOS, ET-1 and its receptors (endothelin A and B), or heme oxygenase 1 in experimental cirrhosis affect the development of hypoxic pulmonary hypertension. We induced cirrhosis in male Sprague-Dawley rats using common bile duct ligation (CBDL) and exposed them to CH (inspired PO2 approximately 76 Torr) or maintained them in Denver (Den, inspired PO2 approximately 122 Torr) for 3 wk. Our data show 1) CBDL-CH rats had a persistent blunted hypoxic pulmonary vasoconstriction similar to CBDL-Den; 2) the development of hypoxic pulmonary hypertension was completely prevented in the CBDL-CH rats, as indicated by normal pulmonary arterial pressure and lack of right ventricular hypertrophy and pulmonary arteriole remodeling; and 3) selective increases in expression of ET-1, pulmonary endothelin B receptor, eNOS, and heme oxygenase 1 are potential mechanisms of protection against hypoxic pulmonary hypertension in the CBDL-CH rats. These data demonstrate that unique and undefined hepatic-pulmonary interactions occur during liver cirrhosis and chronic hypoxia. Understanding these interactions may provide important information for the prevention and treatment of pulmonary hypertension.

Hepatopulmonary syndrome and portopulmonary hypertension in the model for end-stage liver disease (MELD) era

1. How do physicians decide which patients with pulmonary vascular disease will benefit from liver transplantation? 2. Studies on patients with pulmonary vascular disease are limited and the findings and recommendations may not apply to all practice sites. 3. All patients with hypoxemia, liver disease, and pulmonary vasodilation do not have hepatopulmonary syndrome (HPS). 4. Not all patients with hepatopulmonary syndrome will benefit from liver transplantation. 5. The mean pulmonary artery pressure (mPAP) may not be an accurate predictor of mortality in patients with portopulmonary hypertension. 6. The effects of pulmonary vasodilators on the outcome of patients with portopulmonary hypertension (PPHTN) is still unconfirmed but promising.

Hepatopulmonary syndrome

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

Gas exchange mechanism of orthodeoxia in hepatopulmonary syndrome

The mechanism of orthodeoxia (OD), or decreased partial pressure of arterial oxygen (PaO2) from supine to upright, a characteristic feature of hepatopulmonary syndrome (HPS), has never been comprehensively elucidated. We therefore investigated the intrapulmonary (shunt and ventilation-perfusion [VA/Q] mismatching) and extrapulmonary factors governing PaO2 in 20 patients with mild to severe HPS (14 males, 6 females; 50 +/- 3 years old SE) at upright and supine, in random order. We set out a cutoff value for OD, namely a PaO2 decrease > or = 5% or > or = 4 mm Hg (area under the receiver operating characteristic curve, 0.96 each). Compared to supine, 5 patients showed OD (PaO2 change, -11% +/- 2%, -7 +/- 1 mm Hg, P < .05) with further VA/Q worsening (shunt + low VA/Q mode increased from 19% +/- 7% to 21% +/- 7% of cardiac output [QT], P < .05), as opposed to 15 patients who did not (+2% +/- 2%, +1+/- 1 mm Hg) with VA/Q improvement (from 20% +/- 4% to 16% +/- 4% of QT, P < .01). Cardiac output was significantly lower in OD patients in both positions. Changes in extrapulmonary factors at upright, such as increased minute ventilation and decreased QT, were of similar magnitude in both subsets of patients. In conclusion, our data suggest that gas exchange response to OD in HPS points to a more altered pulmonary vascular tone inducing heterogeneous blood flow redistribution to lung zones with prominent intrapulmonary vascular dilatations.

Hepatopulmonary syndrome: role of nitric oxide and clinical aspects

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