Patients with cirrhosis may show ventilation-perfusion (VA/Q) inequality in the absence of any intrinsic heart or lung disease. However, the high cardiac output of cirrhosis generally prevents or minimizes the appearance of a severe degree of arterial hypoxemia. Propranolol has been used to reduce cardiac output and portal pressure in these patients. We wondered whether it might alter arterial oxygenation and reduce O2 transport to tissues. We studied eight patients (three women) 54 +/- 3 (SEM) yr of age before and after intravenous propranolol (0.1 mg/kg followed by 2 mg/h). Cardiac output (QT) fell from 7.8 +/- 0.7 to 6.0 +/- 0.7 L/min (p less than 0.05), and portal pressure was reduced (22 +/- 2 to 19 +/- 2 mm Hg, p less than 0.01). Arterial PO2 did not change (88 +/- 4 to 89 +/- 5 mm Hg) because the fall in mixed venous PO2 (43 +/- 1 to 40 +/- 1 mm Hg, p less than 0.01) that followed the lower QT was counterbalanced by a lower intrapulmonary shunt (multiple inert gas technique) (4 +/- 2 to 2 +/- 1%, p less than 0.05) and a shift of the VA/Q distributions toward a higher VA/Q ratio. Paralleling the fall in QT, oxygen transport to tissues (QO2) was reduced (19 +/- 2 to 14 +/- 1 ml/min/kg, p less than 0.01). However, O2 uptake (VO2) remained constant (3.4 +/- 0.2 to 3.6 +/- 0.2 ml/min/kg) because O2 extraction by the tissues increased appropriately (22 +/- 2 to 28 +/- 1%, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)