Search

Liver cirrhosis is a chronic disease of the liver characterized by formation of connective tissue, degeneration and structural changes of liver tissue, and accumulation of fat and cells within the liver. Symptoms of the disease result from loss of function of liver cells and increased resistance to flow through the liver, leading to portal hypertension (high blood pressure in the portal vein). Patients with liver cirrhosis may have hypoxemia, or abnormally low blood levels of oxygen, in the absence of heart or lung disease. This condition may result from an imbalance between ventilation (the oxygenation of the blood) and perfusion (the supply of oxygen to organs and tissues), often caused by abnormally low blood vessel tone. Ventilation-perfusion inequality may not always be associated with hypoxemia, because the high cardiac output associated with cirrhosis maintains blood oxygen levels. The drug propranolol is used to treat portal hypertension associated with cirrhosis and acts to decreases heart rate and output, thereby lowering blood pressure. However, propranolol may reduce blood oxygen levels through its effect of reducing cardiac output. Alternatively, propranolol may improve blood vessel tone, thereby improving ventilation-perfusion inequality. The effects of propranolol on ventilation-perfusion inequality, blood oxygen levels, and transport to and use of oxygen by tissues were assessed in eight patients with cirrhosis and portal hypertension. Propranolol caused a decrease in cardiac output and blood pressure, but had no effect on blood oxygen levels. The decrease in cardiac output was associated with a decrease in oxygen transport to tissues. However, oxygen uptake by tissue remained constant, because tissue extraction of oxygen increased. These findings show that patients with cirrhosis maintain the normal ability to control oxygen extraction, or removal from blood into tissues, despite the decrease in oxygen delivery to the tissues. (Consumer Summary produced by Reliance Medical Information, Inc.)