Calcium balance study during hemofiltration was performed on four patients treated with chronic hemofiltration three times a week by the post-dilution technique. In each hemofiltration at least 18l of body fluid was replaced in addition to ultrafiltrate for intertreatment body weight gain. The group of 4 patients were treated with 3 kinds of substitution fluid having the calcium concentration of 3.0, 3.5 and 4.0mEq/l, each kind for 2 or weeks in sequence, which resulted in 3 different

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... according to the different Ca concentration. Calcium balance during hemofiltration was affected positively by the calcium concentration of substitution fluid, and negatively by the amount of ultrafiltrate for body weight loss. The amount of phosphate removal, however, was not varied between the 3 treatments. Although serum calcium concentration in each treatment increased during hemofiltration, the increase was not related to calcium balance. On the other hand, a decrease of serum phosphate concentration was correlated to the amount of phosphate removal during hemofiltration. An increase of serum non-ionized calcium concentration which was larger than that of serum ionized calcium concentration, showed a significant correlation with an increase of serum albumin concentration owing to hemoconcentration. PTH level decreased after hemofiltration, which was more closely correlated to an increase in serum ionized calcium than to calcium balance. Positive calcium balance might be obtained in ordinary hemofiltration procedure when calcium concentration of substitution fluid is above 3.5mEq/l.