Correlation between fractional reabsorption of sodium and erythropoietin dose in peritoneal dialysis patients.

Background: Erythropoietin (EPO) deficiency of chronic renal failure (CRF) may be a functional consequence of decreased glomerular filtration rate and fractional reabsorption of sodium (FR(Na)). Decreased FR(Na) reduces renal oxygen consumption and increases tissue oxygen pressure, resulting in less EPO production. We hypothesized that, in CRF patients, there is a positive relationship between EPO production and FR(Na) and that, in such patients receiving EPO, a negative correlation is expected between FR(Na) and EPO dose.

Methods: Creatinine clearance, FR(Na), serum iron, transferrin, transferrin saturation, ferritin, and intact parathyroid hormone (iPTH) levels were measured in 91 peritoneal dialysis patients. The correlation between EPO dose and FR(Na) was studied.

Results: Mean EPO dose was 7076 +/- 4821 units/week and mean FR(Na) was 93.40% +/- 6.14%. A negative correlation was found between EPO dose and FR(Na) (r = -0.28, p < 0.01), and a positive correlation was found between both ferritin and iPTH and EPO dose (r = 0.39, p < 0.001 and r = 0.35, p < 0.002 respectively). After adjusting for the effect of creatinine clearance, ferritin, and iPTH, there was still a significant correlation between EPO dose and FR(Na) (p < 0.05).

Conclusion: In CRF patients there is a negative correlation between FR(Na) and EPO dose, which supports the hypothesis that EPO deficiency may be related to the decreased renal oxygen-consuming work of sodium reabsorption.