We would like to thank Morali and Blendis for their comments (HEPATOLOGY 1990;12:615-617) on our report regarding diminished central blood volume (CBV) and arterial blood volume in patients with cirrhosis (Gastroenterology 1989;97: 1506-1513). Morali and Blendis suggest that pulmonary shunting, especially in the sitting position, may contribute to erroneous short indicator transit time and thus miscalculated small CBV. Based on previous reports on echocardiographic measurements of heart chambers, they conclude that virtually no space exists for a diminished CBV. Finally, they present data suggesting that neurohormonal markers do not indicate central circulatory underfilling in cirrhosis.
Effect of Pulmonury Shunting. The presence of pulmonary right-to-left shunts may shorten the mean circulatory transit time of the indicator, but whether this has any significance on CBV depends on the concurrent changes in cardiac output. Our primary goal was not to assess pulmonary shunting, and the decreased CBV cannot be caused by decreased mean transit time owing to pulmonary shunting, as explained in our appendix. In the upright position, CBV will decrease somewhat. This is caused by the orthostatic effect on central parts of the blood volume and to a decrease in cardiac output (Table 1). In fact, head-up tilting significantlyprolongs the mean transit time even though CBV decreases. We agree that some of the decrease in arterial oxygen saturation could be caused by chronic pulmonary disease caused by smoking and that these patients may desaturate further in the sitting position, but this change in body position will not shorten the mean circulatory transit time, as proposed by Morali and Blendis.
Volumes of Heart Chambers and Lungs. Rector and Hossack (1) and Rector et al. (2) have recently reported increased left atrial diameters in patients with cirrhosis and a nonsignificant increase in right ventricle diameters. However, taking a close look at these figures obtained by echocardiography (left atrial diameter 42 k 6 mm vs. 34 2 5 mm in controls [p c 0.051, right ventricle 21 k 4 mm vs. 7 to 23 mm in normals, left ventricle 49 k 4 ml vs. 35 to 57 mm in normals [ll; left atrial volume 46 k 14 ml vs. 30 k 4 ml in controls