Increased total vascular capacity in conscious cirrhotic rats

The purpose of the present study was to determine the role of the systemic venous circulation in the hemodynamic alterations of the cirrhotic disease. Cardiac output (thermodilution; n = 8), mean circulatory filling pressure (balloon technique; n = 6), and blood volume (Evans blue dye; n = 7) were investigated in a rat model of liver cirrhosis without ascites induced by a 12-week individualized CCl4/phenobarbital treatment. Compared with control rats, conscious cirrhotic rats showed a hyperdynamic circulation characterized by normotension, high cardiac output (51 +/- 4.8 vs. 28.6 +/- 1.3 mL.min-1.100 g-1; P less than 0.01), and expanded blood volume (6.5 +/- 0.15 vs. 5.4 +/- 0.22 mL.100 g-1; P less than 0.05). There were no significant differences between control and cirrhotic rats in mean circulatory filling pressure (6.40 +/- 0.27 vs. 5.99 +/- 0.22 mm Hg, respectively) or in the pressure gradient for venous return (6.17 +/- 0.19 vs. 5.8 +/- 0.21 mm Hg, respectively). To further examine the venous tone, effective vascular compliance was estimated with the vascular filling-blood volume relationship by measuring the vascular filling before and after rapid changes in volume (+/- 8 mL.kg-1). Compliance was similar in both control and cirrhotic rats (3.15 +/- 0.26 and 3.41 +/- 0.21 mL.mm Hg-1), but the vascular filling-total blood volume relationship of the cirrhotic rats was displaced toward the volume axis. In conclusion, the increase in blood volume without changes in mean circulatory filling pressure (or venous tone) of the cirrhotic rats indicates a situation with venodilation and elevated total venous capacity; this is likely to be an important mechanism that could explain the hyperdynamic circulation of the cirrhotic disease.