1999 Volume 32 Issue 7 Pages 1071-1077
Hypotension is frequently encountered during hemodialysis (HD), which may be due to circulation collapse by water removal. However, in some patients, large fluid removal does not induce hypotension, and in others small fluid removal induces hypotension. Therefore, we examined the vascular permeability in hemodialysis patients (Nephron 74: 266, 1996), and found that the vascular permeability varied widely in each patient according to the ANP concentration (Nephron 74: 19, 1996). This calculation required the use of a computer, thus we devised a simple index to determine the changes in circulating plasma volume (CPV), by measuring the total protein concentration (TP) before and after HD.
Assuming that the total amount of circulating protein does not change during HD, CPVB×TPB=CPVA×TPA, where B and A denote before and after HD, respectively. Thus TPB/TPA equals CPVA/CPVB. In 61 stable maintenance HD patients, TP was measured before and after HD every month for 12 to 24 months. When CPVA/CPVB (%ΔCPV) was plotted against the changes of body weight during HD (%ΔBW), a linear correlation was observed (y=3.54x-0.16, r=0.63, p<0.0001, n=992), suggesting that a 1% change in body weight induces 3.5% reduction of circulating plasma volume on average.
When we divided all patients into five groups according to the %ΔCPV/%ΔBW as follows: group I, <0; II, 0-2; III, 2-4; IV, 4-6, and V, >6, the mean value of CTR was significantly higher in groups I and II compared with the other groups, and the reduction rate of MAP during HD was larger in groups IV and V. This finding indicated that in patients with a low %ΔCPV/%ΔBW ratio, the dry weight should be reduced. To confirm this theory, the %ΔCPV/%ΔBW was plotted against CTR. In patients whose CTR changes were less than 5% for two years, no correlation was revealed between the ratio and CTR. However, in patients whose CTR changes were more than 8% for two years, 15 out of 19 patients showed a close linear correlation between the ratio and CTR.
In conclusion, the change in TP before and after HD indicated the change in circulating plasma volume during HD. The change in 1% body weight induced 3.5% reduction of circulating plasma volume on average, and the %ΔCPV/%ΔBW showed a close correlation with CTR, indicating that this ratio was a useful indicator to determine the hemodynamic change during hemodialysis.
