Influence of blood volume on the blood pressure of predialysis and peritoneal dialysis patients treated with erythropoietin

Twenty-seven patients with renal failure (16 on CAPD and 11 predialysis) were treated with erythropoietin. At 12 weeks, the mean haemoglobin concentration (±SEM) in the CAPD patients had increased from 7.07 ± 0.20 to 10.88 ± 0.45 g/dl (two-tailed paired t test, P<0.0001) and in the predialysis patients from 6.90 ±0.35 to 10.05 ± 0.47 g/dl (P< 0.0001). Predialysis patients were taking more antihypertensive medication at baseline. No increase was required in either group after erythropoietin; there was no change in blood pressure in the CAPD patients, though in the predialysis patients the systolic blood pressure rose slightly from 132 to 146 mmHg (P=0.029) and the mean blood pressure from 95 to 103 mmHg (P=0.028). In 12 patients (6 on CAPD and 6 predialysis) the red cell volume, plasma volume, and total blood volume were measured before and after treatment. In the CAPD patients there was a marked expansion of the red cell volume from 912±127 to 1471±222 ml (P=0.004) and a concomitant contraction of the plasma volume from 3932 ±250 to 3178 ±326 ml (P=0.005), leaving the blood volume unchanged from 4843 ± 352 to 4649 ±503 ml. Predialysis patients had a similar expansion of the red cell volume from 733 ± 59 to 1304± 161 ml (P=0.017) but no contraction of the plasma volume (from 3417 ±354 to 3314 ±260 ml), so that the blood volume tended to expand from 4149 ±347 to 4618 ±414 ml (P= 0.053). The mean contraction of the plasma volume in the predialysis group was trivial (− 102 ±214 ml), whereas in the CAPD group it was large (−754 ±158 ml, P=0.034, two-tailed unpaired t test). Thereby the predialysis group experienced an expansion of the total blood volume of 469±186ml, whereas the CAPD group experienced a contraction of the blood volume of −195±189 ml(P=0.031). We conclude that (a) increased blood volume may contribute to the exacerbation of hypertension induced by erythropoietin therapy; (b) gradual reduction of plasma volume, aiming for a stable total blood volume, is an important strategy for the prevention and control of erythropoietin-induced hypertension; (c) as reduction of plasma volume may be more problematic in predialysis patients, adequate blood pressure control may consequently be slightly more difficult, placing more reliance on antihypertensive medication.