New-Onset Anemia and Associated Risk of ESKD and Death in Non-Dialysis CKD Patients: A Multi-Cohort Observational Study

Background

Anemia is a common complication of chronic kidney disease (CKD), but its incidence in nephrology settings is poorly investigated. Similarly, the risks of adverse outcomes associated with new-onset anemia are not known.

Methods

We performed a pooled analysis of three observational cohort studies including 1031 non-anemic CKD patients with eGFR <60 mL/min/1.73 m² regularly followed in renal clinics. We estimated the incidence of mild anemia (hemoglobin 11–12 g/dL in women and 11–13 g/dL in men) and severe anemia (hemoglobin <11 g/dL or use of erythropoiesis-stimulating agents) during a 3-year follow-up period. Thereafter we estimated the risk of end-stage kidney disease (ESKD) and all-cause death associated with new-onset mild and severe anemia.

Results

The mean age was 63 ± 14 years, 60% were men and 20% had diabetes. The mean estimated glomerular filtration rate (eGFR) was 37 ± 13 mL/min/1.73 m² and the median proteinuria was 0.4 g/day [interquartile range (IQR) 0.1–1.1]. The incidence of mild and severe anemia was 13.7/100 patients-year and 6.2/100 patients-year, respectively. Basal predictors of either mild or severe anemia were diabetes, lower hemoglobin, higher serum phosphate, eGFR <30 mL/min/1.73 m² and proteinuria >0.50 g/day. Male sex, moderate CKD (eGFR 30–44 mL/min/1.73 m²) and moderate proteinuria (0.15–0.50 g/day) predicted only mild anemia. The incidence of anemia increased progressively with CKD stages (from 8.77 to 76.59/100 patients-year) and the proteinuria category (from 13.99 to 25.02/100 patients-year). During a median follow-up of 3.1 years, 232 patients reached ESKD and 135 died. Compared with non-anemic patients, mild anemia was associated with a higher adjusted risk of ESKD {hazard ratio [HR] 1.42 [95% confidence interval (CI) 1.02–1.98]} and all-cause death [HR 1.55 (95% CI 1.04–2.32)]. Severe anemia was associated with an even higher risk of ESKD [HR 1.73 (95% CI 1.20–2.51)] and death [HR 1.83 (95% CI 1.05–3.19)].

Conclusions

New-onset anemia is frequent, particularly in patients with more severe renal damage and in those with diabetes mellitus. The occurrence of anemia, even of a mild degree, is associated with mortality risk and faster progression towards ESKD.

Very low protein diet supplemented with ketoanalogs improves blood pressure control in chronic kidney disease

Blood pressure (BP) is hardly controlled in chronic kidney disease (CKD). We compared the effect of very low protein diet (VLPD) supplemented with ketoanalogs of essential amino acids (0.35 g/kg/day), low protein diet (LPD, 0.60 g/kg/day), and free diet (FD) on BP in patients with CKD stages 4 and 5. Vegetable proteins were higher in VLPD (66%) than in LPD (48%). LPD was prescribed to 110 consecutive patients; after run-in, they were invited to start VLPD. Thirty subjects accepted; 57 decided to continue LPD; 23 refused either diet (FD group). At baseline, protein intake (g/kg/day) was 0.79+/-0.09 in VLPD, 0.78+/-0.11 in LPD, and 1.11+/-0.18 in FD (P<0.0001). After 6 months, protein intake was lower in VLPD than LPD and FD (0.54+/-0.11, 0.78+/-0.10, and 1.04+/-0.21 g/kg/day, respectively; P<0.0001). BP diminished only in VLPD, from 143+/-19/84+/-10 to 128+/-16/78+/-7 mm Hg (P<0.0001), despite reduction of antihypertensive drugs (from 2.6+/-1.1 to 1.8+/-1.2; P<0.001). Urinary urea excretion directly correlated with urinary sodium excretion, which diminished in VLPD (from 181+/-32 to 131+/-36 mEq/day; P<0.001). At multiple regression analysis (R2=0.270, P<0.0001), BP results independently related to urinary sodium excretion (P=0.023) and VLPD prescription (P=0.003), but not to the level of protein intake. Thus, in moderate to advanced CKD, VLPD has an antihypertensive effect likely due to reduction of salt intake, type of proteins, and ketoanalogs supplementation, independent of actual protein intake.

Cardiovascular risk factors in severe chronic renal failure: the role of dietary treatment

BACKGROUND

Lipoprotein abnormalities and increased oxidized LDL (OxLDL) are often observed in uremia and are reported to play a central role in the development of cardiovascular disease (CVD). Vegan diet, known for its better lipoprotein profile and antioxidant vitamins content, could protect against CVD. Aim of this study was to investigate the influence of vegan diet supplemented with essential amino acids (EAA) and ketoanalogues (VSD) on both traditional and non-traditional cardiovascular risk factors (CVRF).

METHODS

Twenty-nine patients (18 M, 11 F) aged 55 years (range 29-79 years) with advanced chronic renal failure (median sCr: 5.6 mg/dl) on very low protein vegetarian diet (0.3 g/kg/day) supplemented with a mixture of EAA and ketoacids (VSD) and 31 patients (20 M, 11 F) aged 65 years (range 29 - 82 years) on conventional low-protein diet (CD: 0.6 g/kg/day) with a similar renal function (median sCr: 5.2 mg/dl), were investigated for lipids and apolipoprotein parameters (traditional CVRF) as well as for oxidative stress (oxidized LDL, antibodies against OxLDL and thiobarbituric acid-reactive substances (TBARS)), total homocysteine (tHcy), lipoprotein(a) (Lp(a)), albumin and c-reactive protein (CRP) (non-traditional CVRF) including vitamins A, E, B12 and folic acid.

RESULTS

Compared to patients on CD, those on VSD showed increased HDL cholesterol levels (p < 0.005) with a reduction of LDL cholesterol (p < 0.01) and an increase of apoA1/apoB ratio (p < 0.02). Among non-traditional CVRF, a mild but significant reduction of OxLDL (p < 0.05) with lower TBARS concentrations (p < 0.01) and a significant reduction of total homocysteine (p < 0.002), Lp(a) (p < 0.002) and CRP levels (p < 0.05) were also observed in these patients. Concentrations of vitamin E and A were not different between the two groups while vitamin B12 and folic acid resulted markedly increased in patients on VSD. OxLDL significantly correlated with total and LDL cholesterol, triglycerides and Apo B in CD but not in VSD patients. Patients on CD also showed a significant correlation between urea and CRP. After a multivariate analysis, only urea (p < 0.001) and OxLDL (p < 0.006) were associated to a risk of CRP > 0.3 mg/dl.

CONCLUSIONS

These results indicate a better lipoprotein profile in patients on vegan diet including non-traditional CVRF. In particular, these patients show a reduced oxidative stress with a reduced acute-phase response (CRP) as compared to patients on conventional diet. We hypothesize that urea, significantly lower in patients on VSD, may account, possibly together with the reduction of other protein breakdown products, for the decreased acute-phase response observed in these patients. Our findings suggest that low-protein diets, and vegan in particular, may exert a beneficial effect on the development of cardiovascular disease in patients with end-stage renal disease (ESRD).

[Cystatin C, beta2-microglobulin and C-reactive protein in hemodiafiltration and on-line endogenous liquid reinfusion and in low flux polysulphone bicarbonate conventional hemodialysis]

PURPOSE

Dialysis morbidity results partly from middle and large molecule retention, which is poorly removed by conventional hemodialysis (HD). The potential benefit of convective treatments could be the enhanced toxin removal over a wide molecular weight spectrum. This study aimed to evaluate cystatin C (cis), beta2-microglobulin (beta2-m) and C-reactive protein (CRP) removal behavior during hemodiafiltration reinfusion vs conventional low-flux HD (1.8 m2 low-flux polysulphone) (bicarbonate dialysis (BD)). The molecular weights of the substances evaluated in this study were as follows: cis = 13,300 daltons, beta2-m = 11,818 daltons, CRP = 160,000 daltons.

METHODS

Twelve patients on stable HD (six males, six females), were enrolled; six patients underwent BD and six patients underwent HFR. We measured arteriovenous serum cis, beta2-m and CRP levels, in three consecutive mid-week sessions at the following periods: pre/post-dialysis and after 60 min from the beginning of the session. At 60, 120 and 180 min of HFR, we collected the ultrafiltrate for cis, beta2-m, and CRP evaluation.

RESULTS

Cis, beta2-m and CRP mean values did not differ at pre-dialysis in the two groups. Pre/post- dialysis difference for cis in HFR vs BD was statistically significant (p=0.002) because cis reduced in HFR and increased in BD during the session. Beta2-m and CRP pre/post- dialysis differences in HFR vs BD were not significant. Cis clearance, measured 60 min after the beginning of the session was 34.2 +/- 20.1 mL/min in HFR and 24.8 +/- 18.4 mL/min in BD (p<0.05). beta2-m and CRP clearances did not differ among the treatments. Regarding the ultrafitrate concentrations during the HFR session, cis significantly decreased (2.5 +/- 0.6 mg/dL at 60 min and 2.0 +/- 0.4 mg/dL at 180 min; p=0.004), as well as beta2-m (21.5 +/- 12.9 mg/dL and 19.0 +/- 14.1 mg/dL, respectively; p=0.02). Ultrafiltrate CRP values, as expected, did not differ during HFR.

CONCLUSIONS

This study demonstrated that cis, a middle molecule, is well depurated in HFR, while in BD it increases. Beta2-m, although better removed in the convective phase during HFR, does not demonstrate a removal difference in HFR and in BD. CRP, a large molecule, does not have significant removal. Since cis and beta2-m have almost the same molecular weight, why do they have a different depuration? We need further studies to evaluate if membranes can remove these molecules or if protein electrical charges or their stereoscopy enables their removal.

Oxalate depuration during biofiltration with AN69 and in conventional hemodialysis in chronic renal failure (CRF) patients

Oxalate (Ox), an end product of amino acid metabolism, accumulates in CRF patients as calcium crystal deposits in many soft tissues such as myocardium, kidney interstitium, etc. Since BF employs AN69, a high efficiency membrane, we tested its depurative efficacy for Ox against a hollow-fiber cuprophan dialyzer. Five CRF patients previously in HD and after six months of BF were studied. End-dialysis and pre-dialysis Ox values and dialyzer clearance were obtained. Predialysis Ox values were: 0.44 +/- 0.15 mg/dl in HD and 0.42 +/- 0.09 mg/dl in BF (NS). End-dialysis Ox values were: 0.30 +/- 0.09 mg/dl in HD and 0.22 +/- 0.04 mg/dl in BF (p less than 0.001). Pre and post dialysis values differed by 31% in HD and 47% in BF (p less than 0.001). Ox clearance was 98.8 +/- 10.3 ml/min in HD and 143 +/- 20.5 ml/min in BF. There was a rebound in Ox values at 48 hours (0.41 +/- 0.08 mg/dl in HD and 0.32 +/- 0.12 mg/dl in BF, (NS). These results indicate that Ox is depurated better during BF than during HD.

Serum oxalic acid in uremia: effect of a low-protein diet supplemented with essential amino acids and ketoanalogues

Serum oxalic acid (sOx) was determined with a new, specific enzymatic method in 73 uremic patients and the values were plotted against serum creatinine. 41 patients received a free mixed diet, and 32 similar patients were given a low-nitrogen diet supplemented with essential amino acids, ketoanalogues, and calcium carbonate (AD). A significant correlation was found between serum creatinine and sOx levels in patients following a free mixed diet, while no correlation appeared in patients on AD: The sOx concentrations were significantly lower and even normal in this group, and a significant reduction of sOx occurred in 10 patients with chronic renal failure, who changed from a free mixed diet to the AD. The lowering of sOx concentration in patients following AD is attributed both to low intake of its metabolic precursors and to the oral calcium carbonate supplementation.

Serum uric acid in mild essential hypertension

The mean serum level of urate and the incidence of hyperuricemia have been found to be normal in 85 patients with untreated essential arterial hypertension without renal failure. On the contrary, the incidence of hyperuricemia has been found to be high in 36 similar patients on a low salt diet and in 19 others who received diuretics. Uricemia decreased in 55 patients on a low salt diet who received hydrazinophthalazine (hydralazine) and in 10 other patients who changed their diet from a low salt diet to a diet supplying normal amounts of salt. These results indicate that essential arterial hypertension does not cause hyperuricemia.