PROTEIN LOSSES IN CONTINUOUS RENAL REPLACEMENT THERAPIES

Continuous renal replacement therapy (CRRT) has become a popular treat ment modality but may have the disadvantage of producing substantial p rotein losses. With use of the Biuret method, a relatively insensitive assay, dialysate/ultrafiltrate protein losses have been reported to b e as high as 1.3 g/L. With CRRT outputs of up to 50 L/day, these value s would amount to protein losses of up to 65 g/day. In this study, dia lysate/ultrafiltrate protein losses were reanalyzed by using a highly sensitive microprotein reagent (pyrogallol red) considered to be more accurate than previously available methods. Twenty-two dialysate/ultra filtrate samples were obtained from Amicon-20 Diafilters or Fresenius F-80 dialyzers during continuous venovenous hemofiltration (CVVH) or c ontinuous venovenous hemodialysis/hemodiafiltration (CVVHD/F). Mean ho urly output for all treatments was 1637 +/- 694 mL/h. Mean protein con centration for all 22 dialysate/ultrafiltrate samples was 4.2 +/- 4.0 mg/dL, Mean dialysate/ultrafiltrate protein concentrations were simila r for the Amicon 20 (3.4 +/- 4.4 mg/dL, N = 9) and the Fresenius F-80 (4.7 +/- 3.9 mg/dL, N = 13) (P = not significant). Protein losses were higher during convection-based CVVH (6.0 +/- 5.1 mg/dL, N = 10; range , 1 to 15 mg/dL) than during the mixed convection and diffusion-based CVVHD/F (2.7 +/- 1.9 mg/dL, N = 12; range, 0 to 6 mg/dL) (P = 0.049). Mean serum protein concentration at the time of dialysate/ultrafiltrat e sampling was 4.7 +/- 1.8 g/dL. There was a weak, but statistically s ignificant correlation between the dialysate/ultrafiltrate samples and the corresponding value for serum protein (r = 0.468, P < 0.03). It w as concluded that protein losses during CRRT treatments are substantia lly lower than previously reported, are dependent on the serum protein concentration and the predominant nature of solute removal (convectio n versus diffusion), and can vary between 1.2 and 7.5 g/day.