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      Vitamin C Neglect in Hemodialysis: Sailing between Scylla and Charybdis

      Blood Purification

      S. Karger AG

      Vitamin C, Hemodialysis, Oxalosis, systemic

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          In our efforts to meet the vitamin C requirements of dialysis patients we confront a medical dilemma – do we allow the patient to become depleted of vitamin C, with the accompanying hematological and other consequences (Scylla), or do we provide for adequate tissue levels of vitamin C, which has been thought to carry the risk of oxalosis (Charybdis). Many practitioners are certain that either one outcome (deficiency) or the other (oxalic acid toxicity) is inevitable, and much like Odysseus, no safe course is to be found. The recent accumulating evidence that vitamin C improves the management of anemia in dialysis patients compels us to find a safe passage through this dilemma. The serious vitamin C deficiency seen in many patients may also contribute to poor oral health and chronic fatigue. The evidence for oxalosis from vitamin C supplements stems from hemodialysis as practiced 20 years ago. Investigators using this therapy are not observing systemic oxalosis, and the most current data support the conclusion that vitamin C therapy is safe for dialysis patients. The question will be resolved by controlled trials that address both vitamin C effectiveness and safety.

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          Most cited references 26

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          Convective and diffusive losses of vitamin C during haemodiafiltration session: a contributive factor to oxidative stress in haemodialysis patients.

          Enhanced oxidative stress in haemodialysis (HD) patients may be considered as a risk factor for accelerated atherosclerosis. Reduced antioxidant defences include impairment in enzyme activities and decreased plasma levels of hydrophilic vitamin C (vit C), and cellular levels of lipophilic vitamin E (vit E). We investigated plasma levels of vit C in 19 patients undergoing regular haemodiafiltration (HDF) (mean age 62+/-7 years) and in 1846 healthy elderly subjects (HS) (mean age 69+/-5 years). The contribution of convection and diffusion was determined using paired filtration dialysis (PFD), a modified HDF technique which physically separates convective from diffusive fluxes. Blood samples were collected before and after the HDF session; in addition at 60 min of HDF, samples were drawn from arterial lines (AL) and venous lines (VL), dialysate (D) and ultrafiltrate (UF). Blood levels of total vit C were determined using an HPLC fluorescence method. Markers of oxidative stress were also assessed in both populations as follows: levels of malondialdehyde (MDA) were determined by fluorometric assay, measurements of advanced oxidation protein products (AOPP) and glutathione peroxidase (GSH-Px) activity were performed by spectrophotometric assay, and plasma vit E content was obtained by an HPLC procedure. A significant reduction in plasma vit C level was observed in HDF patients when compared with HS (1.6+/-1.4 microg/ml in HDF vs 6.6+/-3.7 microg/ml in HS; P<0.01). The HDF session was associated with a dramatic reduction in vit C levels (1.87+/-1.57 microg/ml before HDF and 0.98+/-0.68 microg/ml after HDF); at 60 min of HDF, concentrations were as follows: AL=1.35+/-1.27 microg/ml; VL=0.37+/-0.31 microg/ml, D=0.40+/-0.34 microg/ml, UF=1.24+/-1.18 microg/ml; corresponding to a diffusive flux of 271 microg/min and a convective flux of 126 microg/min. Total loss of vit C could be assessed at 66 mg/session (8--230 mg/session). According to this loss of vit C, presence of an oxidative stress was demonstrated in HD population as shown by a significant increase in MDA (1.66+/-0.27 microM in HD vs 0.89+/-0.25 microM in HS; P<0.01) and AOPP (77.5+/-29.3 microM in HD vs 23.5+/-13.2 microM in HS; P<0.01) levels, and a decrease in GSH-Px activity (259.2+/-106.3 U/l in HD vs 661.2+/-92.2 U/l in HS; P<0.01). No change in plasma vit E between both populations (30.7+/-9.1 microM in HD vs 35.3+/-7.34 microM in HS) was observed. These results suggest that HDF with highly permeable membranes is associated with a significant loss of vit C. Diffusive transport is responsible for two-thirds whereas convective phenomenon accounts for only one-third of this loss.
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            Knowledge of dietary restrictions and the medical consequences of noncompliance by patients on hemodialysis are not predictive of dietary compliance.

            To investigate whether knowledge of the diet and medical consequences of noncompliance influences dietary compliance among patients on hemodialysis. An interviewer-administered questionnaire assessed patients' knowledge of foods restricted in their diet (four separate scores for knowledge of foods restricted for: potassium, phosphorus, sodium, and fluid); overall knowledge of restricted foods (one composite knowledge score); and knowledge of medical complications of dietary noncompliance (one composite knowledge score). Patients' mean monthly serum phosphorus and potassium and weight charts provided an estimate of dietary compliance. Seventy-one of the eligible 82 patients on hemodialysis at Nottingham City Hospital, Nottingham, UK, participated in the study (87% response rate). Chi(2) tests determined associations between dietary compliance and knowledge scores. More than one third of patients were noncompliant with at least one dietary restriction. Phosphorus dietary restrictions were the most commonly abused and potassium the least. Patients' knowledge of the medical consequences of noncompliance was poorer than knowledge of renal dietary restrictions (mean scores 29.4%; 74.7%). There was no association between compliance with potassium or sodium/fluid restrictions and knowledge of these dietary restrictions. However, patients with better knowledge about phosphorus were less likely to be compliant (P=.03). Patients with better knowledge about the medical complications of noncompliance were less likely to be compliant for phosphorus (P=.002) and sodium/fluid (P=.008) restrictions. These findings question the value of current dietary education techniques in motivating patients to comply with dietary restrictions. Instead of the more traditional approach of information-giving, effective educational methods that focus on motivating patients to comply with dietary restrictions are needed to improve compliance.
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              Musculoskeletal manifestations of scurvy.

               Olivier Fain (2005)
              Scurvy occurs in individuals who eat inadequate amounts of fresh fruit or vegetables, often because of dietary imbalances related to advanced age or homelessness. Asthenia, vascular purpura, bleeding, and gum abnormalities are the main symptoms. In 80% of cases, the manifestations of scurvy include musculoskeletal symptoms consisting of arthralgia, myalgia, hemarthrosis, and muscular hematomas. Vitamin C depletion is responsible for structural collagen alterations, defective osteoid matrix formation, and increased bone resorption. Imaging studies may show osteolysis, joint space loss, osteonecrosis, osteopenia, and/or periosteal proliferation. Trabecular and cortical osteoporosis is common. Children experience severe lower limb pain related to subperiosteal bleeding. Laboratory tests show nonspecific abnormalities including anemia and low levels of cholesterol and albumin. The finding of a serum ascorbic acid level lower than 2.5 mg/l confirms the diagnosis. Vitamin C supplementation ensures prompt resolution of the symptoms.

                Author and article information

                Blood Purif
                Blood Purification
                S. Karger AG
                December 2006
                14 December 2006
                : 25
                : 1
                : 58-61
                Renal Research Institute, New York, N.Y., USA
                96399 Blood Purif 2007;25:58–61
                © 2007 S. Karger AG, Basel

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                Page count
                References: 39, Pages: 4
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/96399

                Cardiovascular Medicine, Nephrology

                Oxalosis, systemic, Hemodialysis, Vitamin C


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