Abstract
Changes in the diameter of the inferior vena cava (IVC) detected by ultrasonography have recently eenthought to be a good parameter of the right-side cardiac function.To evaluate the significance of the changes in IVC diameter, IVC diameter was recorded by real-time B-mode ultrasonography in 10 patients with chronic uremia undergoing hemodialysis who had no cardiac or respiratory failure, since their circulating blood volume (CBV) was rapidly changed by the removal of water during hemodialysis.
The maximal diameter of the lVC during expiration (IVC-E) and its minimal diameter during inspiration (IVC-I) were measured during quiet respiration just below the IVC-hepatic vein junction, and the respiratory collapsibility index (Cl) was determined (Cl=[IVC-E-IVC-I]/lVC-E). The relationship between these values and changes in the CBV and body weight during hemodialysis was determined.During hemodialysis both the lVC-E and IVC-I were decreased while the CI was increased by the removal of water.Changes in lVC-E (ΔIVC%) were significantly correlated with percent changes in body weight before and after hemodialysis (ΔBW%)(r=0.631, n=65, p<0.001). The IVC-E was also well correlated with changes in the CBV measured in 4 patients by theradio-isotope method (r=0.819, n=20, p<0.001).The IVC-E decreased gradually in accordance with the removal of water during hemodialysis, and reached a plateau at a certain body weight, and the blood pressure fell markedly when more water was removed and the IVC-E decreased to less than the previous plateau level.Saline infusion and/or elevation of both legs returned the blood pressure to the previous level and the IVC dimension increased again.
On the basis of these results, it was concluded that observation of the IVC by B-mode ultrasonography provides useful information for indirect estimation of the CBV and/or body fluid volume. Changes in IVC diameter during hemodialysis would be a reliable indicator for determining the adequate amount of water to be removed by hemodialysis for each patient.
