Hepatopulmonary syndrome (HPS) is defined as clinical triad of liver disease, intrapulmonary vascular dilatation and hypoxemia. It is present in 4-32% of patients with cirrhosis. Its pathogenesis is not well defined, but it is speculated that a combination of factors, such as an imbalance in the response of vascular endothelin receptors, pulmonary microvascular remodeling and genetic predisposition, leads to intrapulmonary vascular dilatation and bacterial translocation1 – 4
Initially the hypoxemia in these patients responds to low-flow supplemental oxygen, but, over time, the need for oxygen supplementation. Currently, no pharmacological intervention can readily improve arterial oxygenation and alter the course of HPS. Thus, liver transplantation is the only effective therapeutic option for its resolution 4 , 5.
The aim of this study was to analyze the blood gas changes data of patients in liver-transplant waiting list.
The study was approved by the Institutional Review Board fulfilling all requirements to retrospective studies in humans.
Clinical data of 279 patients in liver-transplant waiting list in May 2013 were studied. They were analyzed by demographic and laboratorial aspects, and the image findings that determine lung disease (hypoxemia) in these cirrhotic patients.
The statistical analysis was performed using GraphPad Prism Software(r). Differences were considered significant at p<0.05. Data were presented as the mean ± standard deviation (SD) for continuous variables.
There was a high prevalence of men (68%); the mean age was 51(±5,89) years and the predominant reason for listing was hepatitis C cirrhosis. The MELD mean score was 16±5,89, without prioritization or special situation. The most common blood type was O in 129 cases (46%) and the mean of body max index was 25,94±4,58.
Arterial blood gas analysis
Regarding arterial blood gas tests were observed 214 patients with PaO2<90 mmHg, 80 with <80 mmHg and 39 with <50 mmHg. The oxigen saturations (O2 saturation) were in 50 patients <90%, in 33 <80% and in 10 <50% (Figure 1).
Were observed high values of desaturation in this population. Moreover, differential diagnosis must to be done to excluded pulmonary and clinical findings that simulate disease of the lung in end-stage of liver disease.
HPS can normally be diagnosed with non-invasive tests. An elevated alveolar-arterial gradient and decrease in arterial blood gas occurs due to the dilatation of pulmonary vasculature leading to shunt with ventilation-perfusion mismatch 4 – 8.
The majority of patients are either asymptomatic, particularly if diagnosed during evaluation for liver transplantation. Some cases develop the insidious onset of dyspnea7 , 9. In addition, respiratory symptoms are common in end-stage of liver disease owing to poor physical condition, smoking, ascites or other lung disease 4 , 9. Chest radiography, chest CT and pulmonary function tests are often performed to evaluate dyspnea in cirrhosis and during evaluations for liver transplantation10. Commonly, chest radiographic findings are normal in HPS, even when hypoxemia is severe.
No effective medical therapy for HPS is available although a number of related substances have been studied in experimental and human disease 4. Several reports using TIPS to treat HPS were done and others are in progress, but no effective benefit has been presented11. Supplement oxygen is effective to improve dyspnea.
Finally, liver transplantation is the only effective treatment for patients with HPS and complete resolution of gas exchange abnormalities is reported in >80% on them7 , 8. However, an early prospective study found that those with severe HPS (PaO2 of <50 mmHg) had a marked increase in postoperative mortality 4 , 10.
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