Comparison of indirect methods to estimate plasma volume changes during hemodialysis

Changes in plasma volume and intravascular protein mass were studied in a group of patients receiving routine hemodialysis. The methodology involved measuring pre- and post-dialysis hematocrits, total plasma proteins, colloid osmotic pressure, albumin and IgG concentrations. Correlations were sought among the plasma volume changes provided by equations using the listed, measured variables. The differences between predicted and measured post-dialysis protein concentrations were used to estimate net gain or loss of protein. Overall, no net gain or loss of intravascular proteins was observed, but the results raised the possibility that changes in intravascular proteins might occur in individual cases. These measurements may be useful in evaluating patients with recurrent dialysis-induced hypotension.