Raised plasma levels of H2S and nitrate predict intrapulmonary vascular dilations: A preliminary report in patients with cryptogenic cirrhosis

The role of vasoactive chemicals in the pathogenesis of hepatopulmonary syndrome (HPS), a disorder characterized by intrapulmonary vascular dilation (IPVD), is only vaguely elucidated. We aimed to study the association between plasma H2S, nitrate levels, and presence and severity of IPVD and HPS. Consecutive adult patients with cryptogenic cirrhosis were evaluated for IPVD (by contrast echocardiography) and for hypoxemia (by arterial blood gas analysis). Plasma H2S and nitrate levels were measured in these patients. Fifty-eight patients with cryptogenic cirrhosis (male, 45; median age, range, 45, 16–74 years; Child’s class; A, 30; B, 18; C, 10) were enrolled in this study. Thirty-four of the 58 (59%) patients had IPVD and 13 (22%) had HPS (mild, 4; moderate, 5; severe, 2; very severe, 2). Plasma H2S levels were significantly higher in patients with IPVD (19.6, 5.7–83 μmol/L) as compared to patients who had no IPVD (12.3, 0–47 μmol/L; p-value 0.03) with an area under receiver operating characteristic curve of 0.68 (95% CI 0.53–0.84). Plasma H2S levels were higher in patients with IPVD irrespective of liver disease severity. There was a trend for higher plasma nitrate levels in patients with IPVD (47, 15.8–126.4 nmol/mL) as compared to patients who had no IPVD (32.3, 6.9–51.4 nmol/mL; p-value 0.1). Raised plasma H2S and nitrate levels had an additive effect on the presence of IPVD. Neither plasma H2S nor plasma nitrate levels correlated with the degree of hypoxemia. Raised plasma H2S and nitrate levels predict the presence of IPVD in patients with cryptogenic cirrhosis.