Long-term blood pressure control in a cohort of peritoneal dialysis patients and its association with residual renal function

Background. Hypertension is the prime contributor for cardiovascular mortal ity in the dialysis population. Peritoneal dialysis (PD) has been thought t o improve blood pressure (BP) control in the short term, but the long-term benefits are not conclusively proven. We aimed to evaluate the degree of BP control in PD patients in the long term and analyse the factors associated with poor control. Methods. Data of all patients who were initiated on PD at one centre betwee n July 1994 and July 1998 and completed at least 1 year of PD were analysed retrospectively at initiation of PD, at 6 months, and annually thereafter until 5 years or until discontinuation of therapy. Hypertension was defined as per WHO/ISH criteria. A 'Blood Pressure Control Index' was empirically defined to account for the effect of antihypertensives on measured BP. Fact ors associated with poor BP control were analysed. Results. Out of 207 patients (age 57.0 +/- 16.0 years, 103 male, 104 female ) 91.3% were hypertensive at the start of PD. About 33.8% had diabetic neph ropathy. Systolic and mean arterial pressure index improved in early phase reaching a nadir between 6 months and 1 year followed by steady progressive worsening through out the rest or follow up. On multiple linear regression analysis age (P < 0.001). duration of hypertension prior to dialysis (P < 0.001), and declining residual renal function, expressed as both average of urea and creatinine clearance (P = 0.002) and residual urine output (P < 0 .001) were independently associated with poor BP control. Diabetes (P = 0.8 36), peritoneal transport (D/P 4 of creatinine at start) (P = 0.218), perip heral oedema (P = 0.479) and dose of erythropoetin (P = 0.488) were not ass ociated. Conclusions. Initiation of PD results in early improvement of hypertension in end-stage renal disease (ESRD). BP control thereafter deteriorates stead ily with time and this is associated with age, duration of hypertension, an d declining residual renal function. This suggests that hypertension in ESR D patients is a progressive disease primarily related to falling glomerular filtration rate, the preservation of which might improve BP control and po ssibly modify cardiovascular risk.