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Background/Aims: During continuous renal replacement therapy, relevant losses of nutritional substrates, vitamins, and trace elements via the filter may occur. We investigated filter lifetime efficiency during a 72-h treatment period. Methods: This prospective study included 40 patients undergoing citrate continuous veno-venous hemodialysis (CVVHD). The elimination rates were measured at 24, 48, and 72 h. To assess the influence of filter lifetime, we determined substrate loss every 24 h over a 72-h interval. Results: Filter lifetime did not affect the loss of ionized calcium, inorganic phosphate, magnesium, zinc, folic acid, and vitamin B12. Nevertheless, we did observe clinically significant loss of ionized calcium and inorganic phosphate during CVVHD that required supplementation. Conclusions: CVVHD leads to significant loss of ionized calcium and inorganic phosphate that is independent of the filter lifetime.

During continuous renal replacement therapy, achievement of recommended treatment dose is important. However, relevant substrate loss may occur and recommended nutrition during critical illness could not be sufficient for higher dialysis doses. We investigated the correlation of dialysis dose and substrate loss for a broad range of dialysis doses. Forty critically ill patients with acute kidney injury undergoing citrate CVVHD were included in this prospective study. Three different corresponding blood flow (BF) and dialysate flow (DF) rates were applied (BF/DF: 100 ml/min, 2000 ml/h; 80 ml/min, 1500 ml/h; 120 ml/min, 2500 ml/h). Delivered effluent flow rate (DEFR) was calculated and correlated with losses of vitamins, electrolytes, and trace elements during recommended nutritional supplementation. For folic acid, vitamin B12, zinc, inorganic phosphate, and magnesium, no correlation of losses and DEFR was detected. For ionized calcium, a correlation was observed and additional substitution was required. Clinically relevant loss of folic acid, vitamin B12, zinc, inorganic phosphate, and magnesium was not observed for differently used dialysis doses of CVVHD, and the loss was covered sufficiently by daily recommended nutritional supplementation. Increased loss of ionized calcium for higher dialysis doses occurred during citrate CVVHD. Therefore, a strict protocol must maintain calcium homeostasis to avoid calcium depletion.