Relationship between volume status and blood pressure during chronic hemodialysis

Relationship between volume status and blood pressure during chronic hemodialysis.BackgroundThe relationship between volume status and blood pressure (BP) in chronic hemodialysis (HD) patients remains incompletely understood. Specifically, the effect of interdialytic fluid accumulation (or intradialytic fluid removal) on BP is controversial.MethodsWe determined the association of the intradialytic decrease in body weight (as an indicator of interdialytic fluid gain) and the intradialytic decrease in plasma volume (as an indicator of postdialysis volume status) with predialysis and postdialysis BP in a cross-sectional analysis of a subset of patients (N = 468) from the Hemodialysis (HEMO) Study. Fifty-five percent of patients were female, 62% were black, 43% were diabetic and 72% were prescribed antihypertensive medications. Dry weight was defined as the postdialysis body weight below which the patient developed symptomatic hypotension or muscle cramps in the absence of edema. The intradialytic decrease in plasma volume was calculated from predialysis and postdialysis total plasma protein concentrations and was expressed as a percentage of the plasma volume at the beginning of HD.ResultsPredialysis systolic and diastolic BP values were 153.1 ± 24.7 (mean ± SD) and 81.7 ± 14.8mm Hg, respectively; postdialysis systolic and diastolic BP values were 136.6 ± 22.7 and 73.9 ± 13.6mm Hg, respectively. As a result of HD, body weight was reduced by 3.1 ± 1.3kg and plasma volume was contracted by 10.1 ± 9.5%. Multiple linear regression analyses showed that eachkg reduction in body weight during HD was associated with a 2.95mm Hg (P = 0.004) and a 1.65mm Hg (P = NS) higher predialysis and postdialysis systolic BP, respectively. In contrast, each 5% greater contraction of plasma volume during HD was associated with a 1.50mm Hg (P = 0.026) and a 2.56mm Hg (P < 0.001) lower predialysis and postdialysis systolic BP, respectively. The effects of intradialytic decreases in body weight and plasma volume were greater on systolic BP than on diastolic BP.ConclusionsHD treatment generally reduces BP, and these reductions in BP are associated with intradialytic decreases in both body weight and plasma volume. The absolute predialysis and postdialysis BP levels are influenced differently by acute intradialytic decreases in body weight and acute intradialytic decreases in plasma volume; these parameters provide different information regarding volume status and may be dissociated from each other. Therefore, evaluation of volume status in chronic HD patients requires, at minimum, assessments of both interdialytic fluid accumulation (or the intradialytic decrease in body weight) and postdialysis volume overload

Predictors of the progression of renal insufficiency in patients with insulin-dependent diabetes and overt diabetic nephropathy

We designed a prospective, double-blind controlled trial to determine predictors of loss of renal function in patients with insulin dependent diabetes and established nephropathy. A total of 409 insulin-dependent diabetic patients with established nephropathy enrolled in a trial on the effect of Captopril on the rate of progression of renal disease. Baseline demographic, clinical (history and physical) and laboratory parameters were analyzed as risk factors for time to progression. Dichotomous characteristics were compared by Fisher's exact test and continuous characteristics with the Wilcoxon rank-sum test. Univariate proportional hazards regression analysis was used to estimate relative risk of nephropathy progression, and bivariate proportional hazard regression to identify interactions with the treatment group assignment. Multivariate proportional hazard regression was employed to determine which characteristics were independent risk factors. We found that a number of demographic and clinical characteristics were significantly associated with nephropathy progression even after adjustment for treatment group. However, after multivariate analysis, the risk factors that independently predicted progression were onset of IDDM later in life, parental diagnosis of IDDM, the presence of edema, increased mean arterial pressure, and an abnormal electrocardiogram. Likewise, a number of laboratory characteristics were also predictive of nephropathy progression. A low hematocrit, high blood sugar, and higher protein excretion predicted nephropathy progression as did a higher serum creatinine, particularly in the face of a normal serum albumin. In conclusion, this study identifies a number of clinical and laboratory risk factors that can predict which patients with insulin-dependent diabetes with established nephropathy are more likely to sustain a clinically important decrease in renal function over a median follow-up of three years