Failure of hypoxic pulmonary vasoconstriction in patients with liver cirrhosis.

The combination of arterial hypoxemia and low pulmonary vascular resistance in patients with liver cirrhosis is unexplained. Pulmonary microcirculatory dilation, but not gross arterio-venous shunts, has been the usual postmortem finding in patients with liver cirrhosis. When 10 patients with alcoholic liver cirrhosis breathed 10% oxygen in nitrogen, they failed to increase their pulmonary vascular resistance. However, four patients with functional murmurs, three patients with hyperkinetic heart syndrome, six patients with normal pulmonary artery pressures and intracardiac left to right shunts, and five patients with renal failure and anemia all increased their pulmonary vascular resistances when they breathed 10% oxygen in nitrogen. These findings suggested that in liver cirrhosis the normal regulating mechanism (hypoxic vasoconstriction) of the pulmonary circulation may be impaired, resulting in failure of the lung to match perfusion with ventilation.