Evaluation of dialysis dose during combination therapy with peritoneal dialysis and hemodialysis.

Peritoneal dialysis (PD) is effective way to preserve residual renal function (RRF) and should be the first-line dialysis option. However, after the loss of RRF, there are limitations to how well PD alone can control the uremic state. Combination therapy with PD and hemodialysis (PD+HD) is the simplest way to deal with these limitations. The general prescription for PD+HD should be 5-6 days of PD and 1 HD session weekly. To determine the adequacy of PD+HD, we adopted the equivalent renal clearance (EKR), first transforming the weekly PD adequacy index (Kt/V), and then evaluating total clearance from both modalities. However the EKR may overestimate the dialysis dose. To accurately track dialysis dose, we use the total effluent (PD, RRF and HD) sampling method to yield Kt/Vef and creatinine clearance (CCref). In comparing PD+HD with 7 days of PD alone, we found that weekly Kt/Vef increased to 2.27 +/- 0.43 from 1.55 +/- 0.4, and weekly CCref increased to 60.3 +/- 9.2 L/1.73 m2 from 42.0 +/- 7.7 L/1.73 m2 (p < 0.001). In addition, the normalized protein equivalent of nitrogen appearance, percentage creatinine generation rate, and percentage lean body mass also increased (respectively) to 0.93 +/- 0.16 g/kg from 0. 77 +/- 0.14 g/kg daily, to 126.5% +/- 21.2% from 82.6% +/- 17.1 %, and to 66.7% +/- 10.9% from 48.2% +/- 8.9% (p < 0.001). Protein losses in PD+HD were not different from those in PD alone, but serum albumin increased significantly to 3.6 +/- 0.3 g/dL from 3.3 +/- 0.3 g/dL, and serum beta2-microglobulin decreased to 23.5 +/- 11.1 mg/L from 33.3 +/- 11.3 mg/L. The total effluent sampling method can be used to evaluate the dialysis dose in PD+HD. The addition of once-weekly HD improved indices of nutrition, with increases in dialysis dose and serum albumin level. In patients without RRF, PD+HD is recommended as a dialysis regimen to maintain the optimal dialysis dose and good nutrition status without peritoneal deterioration from an increase in the PD fluid volume.