Newly developed circulating blood volume-monitoring system and its clinical application for measuring changes in blood volume during hemofiltration.

Blood and ultrafiltrate electrical resistivities were continuously monitored during hemofiltration. By substituting these values into a previously developed equation that was modified by the authors, the hematocrit value was determined; and blood volume change was obtained from the change in this value. The following facts were discovered as the result of monitoring the blood volume change during treatment: When the body position was changed from the reclining to the sitting position, the blood volume decreased by 4.2 +/- 0.3%. With the body water removal rate kept constant, the body position recumbent, and the subject fasted, the blood volume gradually decreased. However, when the position was changed from reclining to sitting for food intake and once more returned to the supine position after the meal, the blood volume was greatly affected by the change in position and the food intake.