Hepatopulmonary syndrome (HPS) involves liver disease, arterial deoxygenation, and pulmonary vascular dilatation.
The prevalence of HPS in cirrhotic patients varies between 4% and 19%.
Previous studies have used and recommended various threshold values defining arterial deoxygenation.
|Using PaO2 as a cut off produced considerably higher positive predictive values.|
However, it is not known how the prevalence of HPS differs using different cut off values for arterial deoxygenation.
In this study, published in the December issue of Gut, a team of researchers studied 127 patients for the presence of HPS.
They used transthoracic contrast echocardiography for detection of pulmonary vasodilation, pulmonary function tests, and blood gas analysis.
Of the total patients, 98 were included in the study; 34% of these had a positive contrast echocardiography.
The team found that when using an increased alveolar-arterial difference for the partial pressure of oxygen (AaDO2) as an indication of hypoxaemia, the prevalence of HPS was higher (>15 mm Hg, 32%; >20 mm Hg, 31%; and >age related threshold, 28%).
However, using reduced partial pressure of arterial oxygen (PaO2) as a threshold (<80 mm Hg, 19%; <70 mm Hg, 15%; and
Furthermore, using AaDO2 as the cut off, the positive predictive value for a diagnosis of HPS was low (34%, 37%, and 53%, respectively).
In contrast, PaO2 as a cut off had considerably higher positive predictive values (44%, 93%, and 94%, respectively).
Additionally, the team found that by introducing PaO2 <65 mm Hg as the cut off, the positive predictive value increased to 100%.
The researchers determined that dyspnoea was more often present in patients with "clinically significant" HPS (57%) compared with "subclinical HPS" (8%), and patients without HPS (6%).
The Child-Pugh score correlated significantly with the severity of HPS.
Dr Schenk's team concluded, "Defining arterial hypoxaemia in HPS by different, previously used, cut off values for arterial oxygenation leads to a wide variation in the prevalence of HPS in the same sample of cirrhotic patients".