Osteocalcin and Myoglobin Removal in On-line Hemodiafiltration Versus Low- and High-flux Hemodialysis

Background: Removal of medium and large solutes is poor with low-flux (LF-HD) and limited with high-flux hemodialysis (HF-HD) and on-line hemodiafiltration (OL-HDF). In clinical practice, there are few in vivo solute markers. Osteocalcin is a protein with a molecular mass of 5,800 daltons, and myoglobin is a large molecule with a molecular mass of 17,200 daltons. The aim of this study was to evaluate the impact of OL-HDF on in vivo removal of a wide spectrum of solutes (urea, creatinine, osteocalcin, beta2-microglobulin, and myoglobin) in comparison to LF-HD and HF-HD.

Methods: Twenty-three patients (15 men, 8 women) were studied. Every patient underwent three dialysis sessions with routine HD parameters. We compared 1.8-m2 polysulfone LF-HD and 1.8-m2 polysulfone HF-HD versus OL-HDF. Predialysis and postdialysis solute concentrations were measured. The percentage of reduction ratio for each solute was calculated.

Results: Mean values for predialysis osteocalcin, beta2-microglobulin, and myoglobin were 16.3 +/- 21 ng/mL, 27.4 +/- 5 mg/L, and 239 +/- 162 ng/mL in LF-HD, respectively. Urea and creatinine reduction ratios were similar in LF-HD and HF-HD and only 1.2% higher in OL-HDF. Osteocalcin, beta2-microglobulin, and myoglobin reduction ratios for LF-HD were negligible. Mean osteocalcin reduction rates were 54.2% +/- 12% for HF-HD versus 63.5% +/- 9% for OL-HDF (reinfusion volume, 26.8 +/- 5 L/session; P < 0.01). Mean beta2-microglobulin reduction rates were 60.1% +/- 9% for HF-HD versus 75.4% +/- 9% for OL-HDF (P < 0.01). Mean myoglobin reduction rates were 24.5% +/- 6% and 62.7% +/- 9% for HF-HD and OL-HDF, respectively (P < 0.01).

Conclusion: LF-HD does not seem to remove solutes with a molecular weight greater than 5,800 daltons. OL-HDF provides marked enhancement of convection volume and enables a significant increase in osteocalcin and beta2-microglobulin removal. Myoglobin extraction is nil with LF-HD, very low with HF-HD, and only adequate with OL-HDF.