Caring for Patients with Hepatopulmonary Syndrome

Hepatopulmonary syndrome (HPS) is a clinical condition characterized by hypoxemia, microvascular dilations within the pulmonary circulation, and pulmonary arteriovenous malformations in persons with advanced liver disease, mainly caused by cirrhosis and portal hypertension. Although the underlying mechanism has not been well elucidated, it is thought that HPS results from increased arteriovenous shunting (i.e., abnormal passage of blood from arteries to veins without capillary circulation) and microvascular remodeling caused by an imbalance between production and clearance of vasoactive circulating molecules. Microvascular pulmonary dilations compromise the diffusion of oxygen from the alveolar space into the dilated capillaries and disrupts ventilation-perfusion matching, increasing the alveolar-arterial oxygen gradient (A-a gradient; i.e., the difference in alveolar and arterial concentration of oxygen) on room air.

Diagnostic criteria include hypoxemia (i.e., subnormal partial pressure of oxygen in arterial blood [PaO2] less than 60 mm Hg; PaO2 is also known as arterial oxygen saturation) and intrapulmonary vascular dilations confirmed by arterial blood gas analysis and pulmonary imaging (e.g., contrast echocardiography) in patients with evidence of chronic liver disease. Other clinical manifestations associated with HPS include dyspnea on exertion and/or at rest, cyanosis, orthodeoxia (i.e., shortness of breath [SOB] when sitting upright that is relieved by lying down, oxygen desaturation when sitting upright), clubbing of fingers, and cutaneous spider nevi. Patients with HPS may also develop pleural effusions and airflow obstruction.