Hepatopulmonary syndrome (HPS) occurs when intrapulmonary vascular dilatation leads to abnormal arterial gas exchange in the setting of liver disease and/or portal hypertension. 1 Over the past 15 years, HPS has emerged as a relatively common complication of cirrhosis, occurring in 15 to 20% of cases, and is an indication for liver transplantation (LT) in patients with significant hypoxemia. 1 However, many clinical features of HPS that may influence exception to the Model for End-Stage Liver Disease (MELD) scoring system, including standardized diagnostic criteria, pre-and post-LT mortality rates, and rate of progression of hypoxemia, are not fully characterized.
The diagnosis of HPS is based on the presence of hypoxemia on room air due to intrapulmonary vascular dilatation in the setting of liver disease and/or portal hypertension. 1 The prevalence of HPS (range, 12 to 32%) varies depending on whether abnormalities in arterial gas exchange are defined by an abnormal alveolar-arterial oxygen gradient or arterial hypoxemia (PaO 2 ). [2][3][4][5][6][7] For the purpose of considering HPS for MELD exception, arterial hypoxemia (PaO 2 ฯฝ 60 mm Hg) detected in the sitting position (to avoid effects of positional changes on PaO 2 ) is a reasonable standard.
In a large prospective study of 200 LT candidates, pulse oximetry was found to be a useful screening technique for hypoxemia in patients with cirrhosis. 3 The use of a screening oximetry threshold of ี
96% as a trigger for obtaining an arterial blood gas would have detected all patients with a PaO 2 ฯฝ 60 mm Hg and resulted in screening of 14% of the cohort. A proposed screening algorithm is provided in Figure 1. The most sensitive and appropriate screening test to detect intrapulmonary vascular dilatation is microbubble trans-