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

Kidney injury in cirrhosis: pathophysiological and therapeutic aspects of hepatorenal syndromes

Acute kidney injury (AKI) is frequent in patients with cirrhosis. AKI and hyponatraemia are major determinants of the poor prognosis in advanced cirrhosis. The hepatorenal syndrome (HRS) denotes a functional and potential reversible impairment of renal function. Type 1 HRS, a special type of AKI, is a rapidly progressive AKI, whereas the renal function in type 2 HRS decreases more slowly. HRS is precipitated by factors such as sepsis that aggravate the effective hypovolaemia in decompensated cirrhosis, by lowering arterial pressure and cardiac output and enhanced sympathetic nervous activity. Therefore, attempts to prevent and treat HRS should seek to improve liver function and to ameliorate arterial hypotension, central hypovolaemia and cardiac output, and to reduce renal vasoconstriction. Ample treatment of HRS is important to prevent further progression and death, but as medical treatment only modestly improves long-term survival, these patients should always be considered for liver transplantation. Hyponatraemia, defined as serum sodium <130 mmol/L, is common in patients with decompensated cirrhosis. From a pathophysiological point of view, hyponatraemia is related to an impairment of renal solute-free water excretion most likely caused by an increased vasopressin secretion. Patients with cirrhosis mainly develop hypervolaemic hyponatraemia. Current evidence does not support routine use of vaptans in the management of hyponatraemia in cirrhosis.

Cardiac and pulmonary issues in LT assessment candidates

With the incidence of liver disease increasing worldwide, a growing number of patients are being referred for assessment for liver transplant (LT). Unfortunately, the donor pool is not expanding at the same rate, which consequentially results in increasing demand on a finite resource. It is therefore imperative that the candidate who undergoes an LT gets maximal benefit with a resultant maximal increase in life expectancy. This article addresses some of the main cardiac and pulmonary issues that may occur in LT assessment candidates.

Hepatopulmonary syndrome associated with nodular regenerative hyperplasia after liver transplantation in a child

HPS is a significant complication of portal hypertension in children with chronic liver disease and is an established indication for LT. It is characterized clinically by the triad of pulmonary vascular dilatation causing hypoxemia in the setting of advanced liver disease. NRH, a cause of non-cirrhotic portal hypertension, is characterized by diffuse benign transformation of the hepatic parenchyma into small regenerative nodules with minimal or no fibrosis. Development of NRH and HPS in pediatric LT recipients has not been reported, although occasional cases have been reported in adult LT recipients. In this report, we discuss a case of a three-yr-old male who developed HPS, two yr after LT. Pulmonary and cardiac causes for hypoxemia were ruled out by appropriate investigations including a chest X ray, echocardiogram, cardiac catheterization, and a CT angiographic study. The diagnosis of HPS was confirmed via bubble echocardiogram that demonstrated intrapulmonary shunting. Open liver biopsy revealed marked NRH. The patient underwent liver retransplantation that resulted in complete reversal of his pulmonary symptoms and normal oxygen saturations within three months after LT.

Cirrhosis and hepatopulmonary syndrome

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

Pulse oximetry is insufficient for timely diagnosis of hepatopulmonary syndrome in children with liver cirrhosis

OBJECTIVE

To prospectively investigate the prevalence of hepatopulmonary syndrome (HPS), the importance of pulse oximetry in diagnosing HPS, and the longitudinal course after liver transplantation in children with cirrhosis referred for liver transplantation.

STUDY DESIGN

Fifty-six patients aged 1-17 years (mean age, 4.6 ± 5.0 years) with liver cirrhosis were screened for HPS by hyperemic capillary blood gas (CBG) analysis and contrast-enhanced transthoracic echocardiography. Eleven patients were excluded owing to conditions that can produce cardiopulmonary dysfunction, including 5 with cystic fibrosis, 1 with pulmonary arterial hypertension, and 5 with an intracardial shunt. HPS was classified in accordance with the European Respiratory Society Task Force criteria on pulmonary-hepatic disorders. Patient groups were compared for biochemical and clinical characteristics.

RESULTS

Eighteen children (40%) with cirrhosis were intrapulmonary vasodilatation (IPVD)-positive and had a pulse oximetry oxygen saturation level >98%. Two of these patients (11%) exhibited moderate HPS with an elevated alveolar arterial oxygen gradient >15 mm Hg and PaO2 <70 mm Hg; they died before undergoing liver transplantation. The sensitivity and specificity of CBG analysis for detecting elevated alveolar arterial oxygen gradient in children with IPVD was 94% and 53%, respectively. HPS was associated with late hepatoportoenterostomy (P < .04). Liver transplantation led to resolution of HPS in all patients.

CONCLUSION

IPVD is frequent in children with liver cirrhosis (40%). Pulse oximetry is insufficient for timely HPS diagnosis. Pathological CBG analysis data indicate IPVD in the majority of cases, but are imprecise in children aged <2 years. Contrast-enhanced transthoracic echocardiography and CBG analysis are recommended for evaluation of HPS in children with cirrhosis, regardless of liver synthesis capacity and clinical chemistry data.

Liver in cardiopulmonary disease

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