A high calcium-phosphate product is associated with high C-reactive protein concentrations in hemodialysis patients.

BACKGROUND: An elevated CaxPO4 product and C-reactive protein (CRP) have been associated with coronary artery calcification and increased cardiovascular mortality in hemodialysis (HD) patients. However, it has not been defined, so far, whether and how both parameters are related to each other. For this reason we have evaluated in a cross-sectional and in an interventional study the possible correlation between CaxPO4 and CRP and the effect of the correction of a high CaxPO4 on CRP levels. METHODS: 47 uremic patients (age 65 +/- 16 years) on regular chronic HD were selected from a total population of 125 prevalent patients treated at our Institution. Patients had no clinical evidence of either acute infectious or inflammatory diseases for at least 4 weeks before the study. They were on regular bicarbonate HD for 6-329 months (median 42). CRP, hemoglobin (Hb), serum albumin (sAlb), protein catabolic rate (PCRn), serum calcium (Ca), serum phosphorus (PO4), CaxPO4, intact PTH, Kt/V, presence of ischemic heart disease (IHD) and/or peripheral vascular disease (PVD) were recorded. CRP was Ln-transformed in all statistical analyses because of positive skewness. RESULTS: The main findings were: LnCRP 2.17 +/- 0.77 mg/l, Ca 10.1 +/- 0.4 mg/dl, PO4 5.8 +/- 0.6 mg/dl, CaxPO4 59 +/- 6 mg2/dl2, andPTHint 218 +/- 195 ng/ml. 18/47 had IHD, 18/47 PVD. A significant hyperbolic correlation between CaxPO4 and CRP was observed. A piecewise linear regression model analysis identified a break-point for CaxPO4 at 55 mg2/dl2. Comparison of CRP levels after the division of the patients into two groups according to CaxPO4 break-point (group A, CaxPO4 < or = 55 mg2/dl2, n = 16 patients; group B, CaxPO4 >55 mg2/dl2, n = 31 patients) showed that CRP levels were significantly lower in patients in group A (LnCRP 1.43 +/- 0.22 mg/l) than in group B (LnCRP 2.55 +/- 0.67 mg/l, p < 0.0001). Multiple regression analysis bearing LnCRP as dependent variable confirmed CaxPO4 as the most significant variable among the other variables examined. In 22 patients with CaxPO4 > or = 60 mg2/dl2, we performed intensive lowering of the CaxPO4 product in order to reach and maintain a CaxPO4 , or =55 mg2/dl2 for 3 months. At the end of observation, a significant reduction in CaxPO4 and LnCRP was observed (CaxPO4 pre 62.8 +/- 1.9 vs. post 46.3 +/- 6.2 mg2/dl2: p < 0.0001; LnCRP pre 2.32 +/-0.36 vs. post 1.83 +/- 0.14 mg/l: p < 0.0001). No significant variation in the other biochemical parameters was observed. CONCLUSIONS: Our data show that in chronic HD patients in steady clinical conditions with no clinical evidence of either infectious or inflammatory diseases, a high CaxPO4 is associated with high CRP concentrations. Intensive lowering of CaxPO4 reduces CRP

Inter-dialytic variations in blood volume and total body water in uraemic patients treated by dialysis.

BACKGROUND: An optimal balance of sodium and water is one of the most important goals of haemodialysis (HD) therapy. However, while inter-dialytic variations in blood volume (BV) have been well described, very little is known about the dynamics of fluid accumulation and distribution in body compartments during the inter-dialysis period. METHODS: We studied inter-dialysis variations in BV, measured as percent variation of plasma haemoglobin (Hb) concentrations (% triangle up BV) and percent variation of total body water (% triangle up TBW), in 24 uraemic patients treated by standard bicarbonate dialysis. These parameters were determined at the end of the last weekly dialysis (T0), after 24 h (T1), 48 h (T2), and at the beginning of the following dialysis session (T3). At each time point we measured Hb, haematocrit (Hct), serum albumin (sAlb), plasma sodium (Na), plasma potassium (K), blood urea nitrogen (BUN), plasma osmolality (Osm), body weight (BW), systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). All patients were clinically stable and had no evidence of acute blood loss in the 3 weeks before the study. RESULTS: During the inter-dialysis period, there were increases in BUN, K and Osm, but Na did not change. SBP and DBP also did not change. HR tended to decrease, and showed a significant reduction between T0 and T3. TBW increased in a linear fashion whereas BV increased exponentially, showing a slow rise during the first 24 h followed by a greater increase in the following time intervals. This was confirmed by concomitant but opposite percent variations in Hct and sAlb concentrations. CONCLUSIONS: Despite the limitations of the current methodology, our data show that the increase in TBW is redistributed during the long inter-dialysis period and this may prevent the effects of a too premature expansion of the intra-vascular compartment. This is especially evident during the first 24 h after HD, during which % triangle up BV is lowest, indicating a preferential distribution of the fluid load towards the extra-vascular space. During the following time intervals, the extra-vascular compartment refills in conjunction with an exponential expansion of BV that reaches its maximum in the last 24 h before HD.