Differential effects of phosphate binders on pre-dialysis serum bicarbonate in end-stage kidney disease patients on maintenance haemodialysis.

BACKGROUND: Phosphate binders' constituents have alkalotic or acidotic properties and may contribute to acid base balance in haemodialysis patients. This study aimed to investigate the differential effects of phosphate binders on pre-dialysis serum bicarbonate in End Stage Kidney Disease patients on maintenance haemodialysis. METHODS: Stable out-patients having satellite haemodialysis for at least 3 months were retrospectively studied for 18 months, excluding those with other medical causes for metabolic acidosis. Blood results were censored for inpatient episodes, at the time of death, renal transplant or dialysis modality change. Multivariable multilevel mixed-effects linear regression was used and five groups of phosphate binders were compared: Group A(Calcium (Ca) and/or Aluminium (Al) binders); B(Sevelamer hydrochloride (SH) alone); C(lanthanum carbonate (LC) alone); D(SH and Ca/Al), E(LC and Ca/Al). RESULTS: Of 320 patients, 292 were eligible for analysis with a mean follow-up of 15.54 (standard deviation, SD 3.98) months. Similar mean pre-dialysis serum levels of bicarbonate were observed at all 6 month-interval analyses. At 18(th) months, observed mean serum bicarbonate levels in mmol/L were Group B: 21.58 (SD 2.82, P<0.001), C: 23.29 (SD 2.80, P=0.02), D: 21.56 (SD 3.00, P<0.001), and E: 21.29 (SD 3.62, P=0.92) compared with Group A: 22.98 (SD 2.77). Mean serum bicarbonate was related to total SH dose in mmol/L: 22.34 (SD 2.56) for SH <2.5 g/day, 21.61 (SD 2.62) for SH 2.5-4.8 g/day, 21.04 (SD 3.31) for SH >4.8 g/day compared with 22.85 (SD 2.91) for non-users; P-trend<0.001. CONCLUSIONS: Phosphate binders' constituents may contribute to/protect against a predisposition to pre-dialysis metabolic acidosis. This may be dose dependant in patients taking Sevelamer Hydrochloride.

Improving CKD-MBD management in haemodialysis patients: barrier analysis for implementing better practice.

BACKGROUND: Although clinical guidelines exist for optimal levels of serum markers of chronic kidney disease mineral and bone disorder (CKD-MBD), target parameters are not achieved in many haemodialysis (HD) patients. The reason for this evidence-practice gap is unclear and more information from patients and healthcare professionals is required to improve knowledge transfer. We aimed to determine potential barriers by surveying HD patients and staff about awareness and management of CKD-MBD. METHODS: A total of 136 prevalent HD patients, 25 nephrologists and 58 dialysis nurses/technicians were surveyed. Three separate questionnaires included issues of knowledge and awareness of CKD-MBD and factors limiting management (including compliance, medications and general understanding). RESULTS: Of patients surveyed, 84% had heard of phosphate, but 42% were unsure of high phosphate foods and 46% unaware of consequences of elevated phosphate. Twenty-seven percent and thirty-five percent of patients, respectively, had difficulty taking or forgetting to take phosphate binders. Seventy-four percent of patients wanted to know more about CKD-MBD (40% via written material). Of nephrologists surveyed, 76% thought non-compliance with phosphate binders was the main reason for poor control of phosphate (predominantly related to poor patient understanding); 84% thought patients wanted to know more but only 28% provided written material on CKD-MBD. Of dialysis staff surveyed, 63% thought non-compliance with binders explained poor control, the main reason being lack of patient understanding; 88% thought patients wanted to know more but only 17% provided written education. CONCLUSIONS: Implementation of an intensive educational programme, with a multi-faceted approach, for HD patients may promote better control of CKD-MBD and improve achievement of target levels.

Lateral lumbar X-ray assessment of abdominal aortic calcification in Australian haemodialysis patients.

AIM: Vascular calcification is prevalent in patients with chronic kidney disease. Abdominal aortic calcification (AAC) can be detected by X-ray, although AAC is less well documented in anatomical distribution and severity compared with coronary calcification. Using simple radiological imaging we aimed to assess AAC and determine associations in prevalent Australian haemodialysis (HD) patients. METHODS: Lateral lumbar X-ray of the abdominal aorta was used to determine AAC, which is related to the severity of calcific deposits at lumbar vertebral segments L1 to L4. Two radiologists determined AAC scores, by semi-quantitative measurement using a validated 24-point scale, on HD patients from seven satellite dialysis centres. Regression analysis was used to determine associations between AAC and patient characteristics. RESULTS: Lateral lumbar X-ray was obtained in 132 patients. Median age of patients was 69 years (range 29-90), 60% were male, 36% diabetic, median duration of HD 38 months (range 6-230). Calcification (AAC score ≥ 1) was present in 94.4% with mean AAC score 11.0 ± 6.4 (median 12). Independent predictors for the presence and severity of calcification were age (P = 0.03), duration of dialysis (P = 0.04) and a history of cardiovascular disease (P = 0.009). There was no significant association between AAC and the presence of diabetes or time-averaged serum markers of mineral metabolism, lipid status and C-reactive protein. CONCLUSIONS: AAC detected by lateral lumbar X-ray is highly prevalent in our cohort of Australian HD patients and is associated with cardiovascular disease, increasing age and duration of HD. This semi-quantitative method of determining vascular calcification is widely available and inexpensive and may assist cardiovascular risk stratification.

Increased iron requirement in hemodialysis patients on antiplatelet agents or warfarin.

BACKGROUND/AIMS: Many hemodialysis patients receive antiplatelet therapy or warfarin; however, little is known about the effect of this on iron requirements. Given the association of antiplatelet therapy with bleeding we hypothesized that there should be a greater need for iron in such patients, which we tested in this study. METHODS: Retrospective 1-year cohort study of 205 chronic hemodialysis patients. The primary outcome variable was total iron dose, which was analyzed according to antiplatelet/warfarin use. Data were also collected on potential confounders, allowing for both unadjusted and adjusted (multiple regression) analysis. RESULTS: 97/205 patients received antiplatelet/warfarin therapy. This group was older, with a higher incidence of macrovascular disease and diabetes and a higher median C-reactive protein (6.0 vs. 3.75 mg/l). Overall, median iron requirement was 1,300 mg/year. In a multiple regression analysis, antiplatelet/warfarin use was associated with an additional iron requirement of 703 mg (95% confidence interval 188-1,220 mg), with the strongest effect observed in patients with normal inflammatory markers. CONCLUSION: We found a high requirement for iron in patients receiving antiplatelet agents/warfarin. We argue that the most likely mechanism for this association is chronic, low-grade blood loss, although further study is required before causality can be established.