Changes in diurnal blood pressure variation and red cell and plasma volumes in patients with renal failure who develop erythropoietin-induced hypertension.

Hypertension is the most common side-effect of treatment with recombinant human erythropoietin (EPO) for the anemia of chronic renal failure. To elucidate why this occurs in some patients we measured changes in blood volumes and diurnal blood pressure (BP) variation during treatment. Isotope labelled measurements of red cell and plasma volume (RCV and PV) were carried out along with ambulatory BP monitoring before starting EPO and after target hemoglobin (Hb) was reached. RCV did not differ between the patient group developing EPO-induced hypertension (EpHT, n = 11) and the group with no change in BP (NC, n = 13) either before or after treatment. However PV was significantly lower in the EpHT group after treatment (2.97 vs 3.92 litres; p < 0.025). Mean BPs differed little between groups because antihypertensive medications were increased as necessary for clinical safety but after achieving target Hb, day-night difference in diastolic BP was greater in the EpHT than the NC group (11.5 vs 4.6 mmHg; p < 0.025) due to a greater rise in daytime BP. There were significant correlations between high day-night diastolic BP differences after EPO in all the studied patients and low plasma volumes either pre- or post-EPO. The study group was heterogeneous but the changes were in the same direction irrespective of type of renal replacement therapy. These results suggest that EPO-induced hypertension is associated with increased daytime vasoconstriction and greater hemoconcentration due to lower plasma volume.