Amino acid removal in high-flow and conventional continuous hemodiafiltration

OBJECTIVE

Continuous hemodiafiltration is frequently used in intensive care as renal replacement therapy for acute kidney damage. Recent studies have shown that increased flow rates can effectively increase survival. However, continuous hemodiafiltration also removes essential small molecules such as amino acids.

METHODS

We compared amino acid loss between conventional (normal-flow) and high-flow continuous hemodia-filtration in 17 patients admitted to the intensive care unit for conditions such as sepsis. Patients were randomly divided into a normal-flow group (dialysate flow, 500 mL/min; filtrate flow, 300 mL/min; and blood flow, 80 mL/min) and a high-flow group (dialysate flow, 1,500 mL/min; filtrate flow, 900 mL/min; blood flow, 100 mL/min). Blood samples were collected immediately prior to continuous hemodiafi initiation, and at 2 and 6 hours after con-tinuous hemodiafiltration initiation. In addition, blood and filtrate were collected from the circuit in front of and behind the continuous hemodiafiltration dialyzer.

RESULTS

We found that amino acid removal was significantly higher in the high-flow group and that amino acids were removed into the filtrates in proportion to their plasma concentrations. Furthermore, plasma amino acid con-centrations also tended to decrease with the length of time continuous hemodiafiltration was performed. Given that large amounts of amino acid are removed during continuous hemodiafiltration, plasma amino acid levels should be monitored when prolonged continuous hemodiafiltration is performed.

CONCLUSIONS

Amino acid loss is particularly high during high-flow continuous hemodiafiltration, suggesting that it may be necessary to shorten the duration of high-flow continuous hemodiafiltration or supplement patients with sufficient amounts of amino acids.