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 11predialysis) were treated with erythropoietin. At 12 weeks,the mean haemoglobin concentration (±SEM) in the CAPDpatients had increased from 7.07 ± 0.20 to 10.88 ±0.45 g/dl (two-tailed paired t test, P<0.0001) and in thepredialysis patients from 6.90 ±0.35 to 10.05 ±0.47 g/dl (P< 0.0001). Predialysis patients were taking moreantihypertensive medication at baseline. No increase was requiredin either group after erythropoietin; there was no change inblood pressure in the CAPD patients, though in the predialysispatients the systolic blood pressure rose slightly from 132to 146 mmHg (P=0.029) and the mean blood pressure from 95 to103 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 andafter treatment. In the CAPD patients there was a marked expansionof the red cell volume from 912±127 to 1471±222ml (P=0.004) and a concomitant contraction of the plasma volumefrom 3932 ±250 to 3178 ±326 ml (P=0.005), leavingthe blood volume unchanged from 4843 ± 352 to 4649 ±503ml. Predialysis patients had a similar expansion of the redcell volume from 733 ± 59 to 1304± 161 ml (P=0.017)but no contraction of the plasma volume (from 3417 ±354to 3314 ±260 ml), so that the blood volume tended toexpand from 4149 ±347 to 4618 ±414 ml (P= 0.053).The mean contraction of the plasma volume in the predialysisgroup was trivial (– 102 ±214 ml), whereas in theCAPD group it was large (–754 ±158 ml, P=0.034,two-tailed unpaired t test). Thereby the predialysis group experiencedan expansion of the total blood volume of 469±186ml,whereas the CAPD group experienced a contraction of the bloodvolume of –195±189 ml(P=0.031). We conclude that (a) increased blood volume may contribute tothe exacerbation of hypertension induced by erythropoietin therapy;(b) gradual reduction of plasma volume, aiming for a stabletotal blood volume, is an important strategy for the preventionand control of erythropoietin-induced hypertension; (c) as reductionof plasma volume may be more problematic in predialysis patients,adequate blood pressure control may consequently be slightlymore difficult, placing more reliance on antihypertensive medication.