Vitamin B6 requirements of patients on chronic peritoneal dialysis

Water-soluble vitamins and trace elements in children with chronic kidney disease stage 5d

Children receiving maintenance dialysis (chronic kidney disease (CKD) stage 5d) have unique risk factors for micronutrient deficiency or toxicity. Children receiving chronic dialysis often require specialized diet plans that may provide more than the recommended daily allowance (RDA) of water-soluble vitamins and micronutrients, with or without the addition of a kidney-friendly vitamin. The following is a comprehensive review of current literature on disorders of micronutrients in this population including those of water-soluble vitamins (vitamin C and vitamin B complexes) and trace elements (copper, selenium, and zinc) and has three areas of focus: (1) the risk factors and clinical presentations of disorders of micronutrients, both deficiency and toxicity, (2) the tools to evaluate micronutrient status, and (3) the central role of renal dietitians in optimizing nutritional status from a micronutrient perspective.

Water soluble vitamins and peritoneal dialysis - State of the art

This review presents the results of a systematic literature search concerning water soluble vitamins and peritoneal dialysis modality. We provide an overview of the data available on vitamin requirements, dietary intake, dialysis related losses, metabolism and the benefits of supplementation. We also summarise the current recommendations concerning the supplementation of vitamins in peritoneal dialysis and discuss the safety of an administration of vitamins in pharmacological doses.

Association of aspartate aminotransferase with mortality in hemodialysis patients

BACKGROUND

Liver disease is a common comorbid condition in maintenance hemodialysis (MHD) patients and may be associated with poor survival. The relationship between aspartate aminotransferase (AST) and survival has not yet been addressed in these patients. We hypothesized that higher AST level is associated with higher death risk in MHD patients.

METHODS

A 5-year (January 2007-December 2011) cohort of 109 718 MHD patients was studied in the USA in dialysis clinics where AST was measured in at least 50% of all outpatients in the baseline calendar quarter. Survival models were adjusted for demographic variables, and available clinical and laboratory surrogates of malnutrition-inflammation complex, and cubic survival splines were plotted.

RESULTS

A linear association existed between baseline serum AST levels and mortality. Increasing AST of >20 IU/L was incrementally and almost linearly associated with higher death risk at all levels of adjustment. In fully adjusted models, AST levels of ≥40 IU/L were associated with the highest risk of mortality (hazard ratio: 1.46, 95% CI: 1.38-1.54). Low AST levels (<15 IU/L) were associated with increased death risk only in fully adjusted models examining hepatitis C virus-positive patients.

CONCLUSIONS

Higher AST level of >20 IU/L is incrementally associated with higher mortality in MHD patients whereas AST in the 15-20 IU/L range is associated with the greatest survival. These findings suggest that the assessment of liver function and improving liver disease may confer survival benefit to MHD patients.

Clinical use of cyclooxygenase inhibitors impairs vitamin B-6 metabolism

BACKGROUND

A low circulating vitamin B-6 concentration, which is an independent risk factor for cardiovascular disease, is commonly seen in human inflammation.

OBJECTIVE

We investigated whether cyclooxygenase inhibitors alter vitamin B-6 metabolism.

DESIGN

To investigate whether subjects taking a cyclooxygenase inhibitor had an altered vitamin B-6 profile, we conducted a cross-sectional study that involved 150 rheumatoid arthritis patients, with and without cyclooxygenase inhibitor treatments. C57BL/6J mice and hyperlipidemic Syrian hamsters received drug regimens that reflected clinical nonsteroidal antiinflammatory drug (NSAID) uses in treating human inflammation. The impact of long-term physiologic use of selective and nonselective cyclooxygenase inhibitors on vitamin B-6 metabolism was systematically investigated in these independent in vivo models.

RESULTS

Patients who were taking cyclooxygenase inhibitors had lower circulating pyridoxal-5'-phosphate, especially those taking NSAIDs >6 mo. Long-term celecoxib and naproxen use reduced hepatic pyridoxal-5'-phosphate in mice. Nonselective cyclooxygenase inhibitor naproxen significantly decreased vitamin B-6 vitamers in the kidney.

CONCLUSIONS

To our knowledge, we show novel findings that long-term physiologic doses of cyclooxygenase inhibitor may impede the synthesis of the coenzymatically active form of vitamin B-6. Because the cause of vitamin B-6 depletion in inflammation remains unknown, this study provides a potential mechanism that could account for the poor vitamin B-6 status in human inflammation. Moreover, this study further raises concerns about the long-term clinical use of antiinflammatory NSAIDs in humans. Vitamin B-6 status should be carefully monitored in long-term NSAID users. Future randomized placebo-controlled studies are needed to determine the impacts of antiinflammatory cyclooxygenase inhibitor use on vitamin B-6 metabolism in humans.

Tuberculosis in haemodialysis patients: A single centre experience

We prospectively followed-up new patients of tuberculosis while on maintenance hemodialysis at a State Government-run tertiary care institute. Between 2000 and 2010, 1237 new patients were initiated on maintainence hemodialysis. The number of patients diagnosed with tuberculosis after initiation of hemodialysis was 131 (10.5% of 1237). The age was 46.4 ± 10.4 (range 8-85) years and there were 90 (68.7%) males. The number of patients diagnosed with tuberculosis on the basis of organ involvement were: Pulmonary-60, pleural effusion-31, lymph node-21, meningitis-8, pericardial effusion-7, peritoneum-2, latent tuberculosis-2. The incidence of tuberculosis in hemodialysis was found to be 105.9 per 1000 patient years. Male gender, diabetes mellitus, past history of tuberculosis, mining as an occupation, low serum albumin, and duration of hemodialysis more than 24 months, and unemployment were found to be significant risk-factors on univariate analysis.

Water-soluble vitamins in people with low glomerular filtration rate or on dialysis: a review

People with low glomerular filtration rate and people on dialysis are spontaneously at risk for vitamin deficiency because of the potential for problems with decreased appetite and decreased sense of smell and taste, leading to decreased intake, and because decreased energy or decreased cognitive ability results in difficulties in shopping and cooking. Imposed dietary restrictions because of their renal dysfunction and because of comorbidities such as hypertension and diabetes exacerbate this problem. Finally, particularly for water-soluble vitamins, loss may occur into the dialysate. We did not identify any randomized trials of administering daily doses close to the recommended daily allowances of these vitamins. In people who are eating at all, deficiencies of B5 and B7 seem unlikely. It is unclear whether supplements of B2 and B3 are necessary. Because of dialyzability and documented evidence of insufficiency in dialysis patients, B1 supplementation is likely to be helpful. B6, B9, and B12 are implicated in the hyperhomocysteinemia observed in patients on dialysis. These vitamins have been studied in combinations, in high doses, with the hope of reducing cardiovascular outcomes. No reductions in patient-important outcomes were seen in adequately powered randomized trials. Because of their involvement in the homocysteine pathway, however, supplementation with lower doses, close to the recommended daily allowances, may be helpful. Vitamin C deficiency is common in patients on dialysis who are not taking supplements: low-dose supplements are warranted. Vitamins for dialysis patients contain most or all of the B vitamins and low-dose vitamin C. We are not aware of any medical reasons to choose one over another.

Vitamin B6 and oxalic acid in clinical nephrology

OBJECTIVE

Vitamin B(6) (VB(6)) is a water-soluble vitamin, which is important for the normal functioning of multiple organ systems. It is metabolized to the active molecule pyridoxal-5-phosphate (PLP). Oxalic acid (OA) is thought to be a uremic toxin that participates in the pathogenesis of the uremic syndrome. The objectives of this study were as follows: (1) to evaluate the plasma and erythrocyte VB(6) (effect of PLP; effect of PLP was in indirect relationship with the concentration of erythrocyte VB(6)), and plasma and urinary OA in marathon runners, in patients with acute intermittent porphyria (AIP) and variegate porphyria, and in patients with stage 1 chronic kidney disease (CKD), chronic glomerulonephritis and nephrotic syndrome (CGNS); (2) to examine the influence of water diuresis in healthy subjects, and the influence of sodium diuresis (high sodium intake) and an intravenous administration of furosemide on the urinary excretion of VB(6) and OA in CKD stage 3-4 patients; and (3) to evaluate the influence of erythropoietin treatment on erythrocyte VB(6) (effect of PLP) in hemodialysis (HD) patients, and the influence of continuous ambulatory peritoneal dialysis (CAPD) therapy on plasma VB(6) and OA and their peritoneal clearance and transfer.

DESIGN AND SETTING

This study was conducted at the Nephrological Clinic of L. Pasteur Faculty Hospital and of Medical School of P. J. Safarik University. A combination of 29 marathon runners, 15 patients with CG and NS, 11 patients with AIP, 1 patient with variegate porphyria, 15 healthy subjects, 27 CKD stage 3-4 patients, 30 HD, and 27 CAPD patients were used in the study.

RESULTS

After a marathon run, plasma and erythrocyte VB(6) significantly decreased and plasma OA increased. Plasma (15.5 +/- 3.8 nmol/L) and erythrocyte VB(6) (effect of PLP: 42.1% +/- 7.5%) were decreased and plasma OA (9.8 +/- 2.3 micromol/L) was significantly elevated in patients with CGNS and stage 1 CKD. In patients with AIP, deficiency of plasma (24.3 +/- 5.2 nmol/L) and erythrocyte VB(6) (effect of PLP: 46.2% +/- 7.0%) and hyperoxalemia (9.39 +/- 2.5 micromol/L) were present. The urinary excretion of VB(6) and of OA during maximal water diuresis and after intravenous administration of furosemide increased significantly (P < .01), but was not affected by the high intake of NaCl (P > .05). Erythropoietin treatment in HD patients led to the erythrocyte VB(6) deficiency. This finding is an indirect evidence that erythrocyte VB(6) is consumed by the hemoglobin synthesis much more during EPO treatment. In CAPD patients, plasma value of VB(6) (127.3 +/- 66.9 micromol/L) was in the normal range and plasma OA (23.6 +/- 7.4 micromol/L) was significantly elevated. Mean value of peritoneal clearance of VB(6) was 8.8% and of OA was 76.9% of urea clearance.

CONCLUSION

Our study indicates that deficiency of VB(6) led to hyperoxalemia and hyperoxaluria in patients with CKD. Deficiency of VB(6) in CKD stage 4-5 patients potentiates the uremic hyperoxalemia and hyperoxaluria.

Dietary intakes and biochemical status of B vitamins in a group of children receiving dialysis

OBJECTIVE

We investigated the dietary intake and biochemical status of B vitamins (thiamin, riboflavin, vitamin B6, and vitamin B12) in a group of mainly unsupplemented children with endstage renal disease receiving dialysis, to determine if B vitamin supplementation is indicated.

DESIGN

This was a cross-sectional, observational clinical trial.

SETTING

Children with endstage renal disease were receiving dialysis, under the care of Renal Services, at Starship Children's Health (Grafton, Auckland, New Zealand).

PATIENTS

We studied 12 children (including 7 girls, and 8 children receiving peritoneal dialysis) mean age 7.8 +/- 5.3 years (SD).

INTERVENTION

Three-day diet records were collected and analyzed with FoodWorks software. Blood was collected for vitamin assay testing.

MAIN OUTCOME MEASURE

Dietary intake of B vitamins was measured as a percentage of recommended dietary intake (RDI) or adequate intakes (AIs) for age. Biochemical status was measured as the concentration of each B vitamin compared with reference ranges.

RESULTS

Mean intakes from diet alone comprised <100% of the RDI or AI for each B vitamin. Mean intakes, with nutritional support, reached >100% of the RDI or AI for each B vitamin. All children achieved >100% RDI or AI for thiamin, riboflavin, and vitamin B12. Two children who were not receiving nutritional support received <100% of the RDI for vitamin B6. Blood levels of B vitamins were normal to high, compared with reference ranges, for each B vitamin in all children, indicating adequate status.

CONCLUSIONS

Intakes were adequate in the majority of children. Status was adequate in all children. In this group of children undergoing dialysis, B-vitamin supplementation was not indicated.

Gamma glutamyltranspeptidase activity and viral hepatitis in dialysis population

BACKGROUND

Numerous investigations have reported that viral hepatitis is associated with significant hepatocellular damage, as expressed by raised aminotransferases in serum, in dialysis population. However, scarce information exists on the activity of gamma glutamyltranspeptidase (GGTP) in dialysis patients with infection by hepatotropic viruses.

OBJECTIVES

We measured serum GGTP values in a large cohort (n=757) of patients receiving long-term dialysis; healthy controls were also included. The relationship between GGTP values and a series of demographic, clinical, and biochemical parameters was analyzed.

METHODS

Serum GGTP levels were tested by spectrophotometry. A subset (n=333) of dialysis patients was tested by molecular technology (branched-chain DNA (bDNA) assay) to evaluate the relationship between serum GGTP and HCV viremia. A subgroup (n=78) of dialysis patients was analyzed by an ultrasound scan of gallbladder and biliary tract to assess the presence of gallstone disease. Multivariate analyses were made using regression models; serum GGTP values were included as a dependent variable. The usefulness of serum GGTP levels in detecting HBsAg and anti-HCV positivity was evaluated using receiver operating characteristics (ROC) curve analysis.

RESULTS

Univariate analysis showed that serum GGTP levels were significantly higher in HBsAg positive and/or anti-HCV positive patients than in HBsAg negative/anti-HCV negative patients on dialysis; 85.1+/-184.1 versus 25.86+/-23.9 IU/l (P=0.0001). The frequency of raised GGTP levels was 22.2% (41/184) among dialysis patients with chronic viral hepatitis. Multivariate analysis showed a significant and independent association between serum GGTP values and positive HBsAg (P=0.005) and anti-HCV antibody (P=0.0001) status. Mean GGTP values were significantly higher in study patients than controls, 32.32+/-60.02 versus 23.5+/-16.92 IU/L (P=0.01); however, no significant difference with regard to GGTP between study and healthy cohorts persisted after correction for age, gender, race, and viral markers. No relationship between gallstone disease and serum GGTP was found (NS). An independent and significant association (P=0.0291) between raised GGTP levels and detectable HCV RNA in serum was noted among patients tested by biology molecular techniques. ROC technology demonstrated that GGTP was equally useful for detecting HBV (P=0.0004) and HCV (P=0.0005) among dialysis patients.

CONCLUSIONS

We found an independent and significant association between serum GGTP values and HBsAg and/or anti-HCV antibody in dialysis population. Twenty-two percent of dialysis patients with chronic viral hepatitis had elevated GGTP. No difference in GGTP between HBsAg- negative/anti-HCV- negative dialysis patients and healthy individuals was found. Routine testing for serum GGTP levels to assess liver disease induced by hepatotropic viruses or other agents in dialysis population is suggested.

Pyridoxine (vitamin B6) toxicity: enhancement by uremia in rats

Pyridoxine is not completely innocuous. Large doses can cause a peripheral neuropathy despite renal excretion of this water-soluble vitamin. Renal failure patients are treated with pyridoxine to prevent a deficiency. The safety of pyridoxine treatment in the presence of renal dysfunction has not been studied. Our experiments on anephric rats show that the uremic state, in a mere 3 or 4 days, causes a 5- to 10-fold increase in susceptibility to pyridoxine-induced neuronopathy. These results suggest a need for caution in prescribing pyridoxine to uremic patients who will probably take the vitamin daily for many years.

Independent effects of residual renal function and dialysis adequacy on dietary micronutrient intakes in patients receiving continuous ambulatory peritoneal dialysis

BACKGROUND

Dialysis patients are at risk of vitamin and mineral deficiencies, not only because of losses during chronic hemodialysis or peritoneal dialysis but also because of low intakes.

OBJECTIVE

The objective was to determine the importance of urea clearance (calculated as K(t)/V) and residual renal function (RRF) in predicting micronutrient intakes in a large cohort of patients receiving continuous ambulatory peritoneal dialysis (CAPD).

DESIGN

We conducted a survey of dietary intakes in 242 CAPD patients and divided them into 3 groups according to their weekly urea clearance and RRF: WD group (n = 84), a urea clearance >/= 1.7 and a glomerular filtration rate (GFR) >/= 1 mL x min(-1) x 1.73 m(-2); DD group (n = 71), a urea clearance >/= 1.7 and a GFR < 1 mL x min(-1) x 1.73 m(-2); and ID group (n = 87), a urea clearance < 1.7.

RESULTS

Most of the patients had intakes of water-soluble vitamins and minerals that were lower than the recommended dietary allowance; most intakes were significantly higher in the WD group than in the DD and ID groups, except those of niacin and calcium. After age, sex, body weight, and the presence of diabetes were controlled for, total weekly urea clearance and the GFR (but not peritoneal dialysis urea clearance) were significantly associated with intakes of vitamins A and C, the B vitamins, and minerals (calcium, phosphate, iron, and zinc). Low intakes of vitamins and minerals with low RRF and urea clearance were the result of reduced overall food intakes, except for thiamine, vitamin B-6, and folic acid, which were deficient in the diet.

CONCLUSIONS

Supplementation with most water-soluble vitamins and minerals, including iron and zinc, should be considered in CAPD patients, especially those with low RRF and low urea clearance. The optimal dose needs to be determined.

Mycobacterial infections in patients with chronic renal disease

In this article, the authors have provided a comprehensive review of TB and MOTT infections in patients on renal dialysis and receiving kidney transplants. Because most published series are small retrospective studies or case reports, there are several uncertainties still involved in the diagnosis and treatment of such patients. Unanswered questions include selection of optimal dosage and duration of therapeutic agents; the best tests for screening and diagnosis, especially in high prevalence areas; and the best management of MOTT infections because of unavailability of highly effective therapy.

Vitamin B6 supplementation can improve peripheral polyneuropathy in patients with chronic renal failure on high-flux haemodialysis and human recombinant erythropoietin

BACKGROUND

High-flux haemodialysis (HD) has recently been vigorously promoted as a novel standard, and it can indeed efficiently reduce the occurrence of most uraemic symptoms due to middle molecular toxins and/or underdialysis. However, some symptoms remain problematical, particularly peripheral polyneuropathy (PPN). One of the possible reasons for this is that the patients may have low concentrations of some nutrients, e.g. vitamin B(6), necessary for normal peripheral neuron function.

METHODS

Predialysis serum pyridoxal-5'-phosphate (P5P) level was determined in 36 chronic HD patients who were undergoing high-flux HD and receiving human recombinant erythropoietin. Among them, 26 patients suffered from PPN. Prior to supplementation, these 26 patients were examined and their neurological symptoms were ranked according to our PPN symptom score. Vitamin B(6) (60 mg/day) was randomly prescribed to 14 of them, and vitamin B(12) (500 microg/day) was prescribed to the others. After 4 weeks, all the patients were re-examined.

RESULTS

We found that predialysis serum P5P levels of HD patients with PPN were not significantly lower than those of matched HD patients without PPN. Nonetheless, it was demonstrated that supplementation with vitamin B(6) for 4 weeks significantly increased the predialysis level of P5P and dramatically attenuated PPN symptoms compared with initial symptoms. No improvement was observed in response to vitamin B(12) supplementation.

CONCLUSION

This result suggests that although vitamin B(6) deficiency could not be demonstrated in patients with chronic renal failure on high-flux HD, vitamin B(6) supplementation was effective in improving PPN symptoms of various aetiologies, possibly because of vitamin B(6) resistance to PPN in these patients.

Oral vitamin intake in children receiving long-term dialysis

OBJECTIVE

To evaluate dietary and oral supplement vitamin intake in children submitted to dialysis (peritoneal dialysis and hemodialysis).

DESIGN

Prospective clinical trial in a 12-month follow-up period.

SETTING

Children with end-stage renal disease (ESRD) who attended the pediatric nephrology clinic of Universidade Federal de São Paulo-Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil.

PATIENTS

Thirty children (18 girls, 23 in peritoneal dialysis, 7 in hemodialysis) with age 9.3 +/- 7.4 years. INTERVENTION METHODOLOGY: Six successive assessments of both anthropometric indexes and 3-day dietary diaries in children receiving a daily dose of oral water-soluble vitamin supplement.

MAIN OUTCOME MEASURES

Anthropometric indexes (weight/age [W/A], height/age [H/A], midarm muscle area/age [MAMA/A], and fat area/age [FA/A]) and dietary adequacy-% recommended dietary allowance (RDA) (computerized nutritional analysis from 3-day dietary intake diary).

RESULTS

Anthropometric indexes analysis showed that 53% of children were <-2.0 standard deviation score (SDS) of W/A, 63% were <-2.0 SDS of H/A, and 43.3% were <-1.65 SDS of MAMA/A, suggesting growth deficit and low muscle wasted. Total caloric intake was lower than 100% of RDA in 90% of children. Dietary intake of water-soluble vitamins was <100% of RDA in the majority of children, as follows: vitamin C (24/30), B1 (28/30), B2 (22/30), B3 (27/30), B6 (26/30), B12 (1/30), pantothenic acid (24/30), and folic acid (9/30). The combined dietary and vitamin supplement intake resulted in excessive oral intake for almost all the vitamins.

CONCLUSION

Dietary intake of water-soluble vitamins is lower than the RDA in the majority of children with ESRD; supplementation is necessary to reach the RDA. The use of the available vitamin supplement resulted in vitamin intakes that exceeded the RDA for almost all of the vitamins. However, we do not know if these intakes exceeded the children's requirements, nor whether they had any clinically significant harmful effects.

Hypoaminotransferasemia in patients undergoing long-term hemodialysis: clinical and biochemical appraisal

BACKGROUND & AIMS

It has been reported that patients with chronic renal failure have low serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels as a result of vitamin B6 deficiency. Chronic hepatitis C is common among patients undergoing hemodialysis, and low aminotransferase levels cause diagnostic problems. The aim of this study was to determine the cause of hypoaminotransferasemia.

METHODS

Serum levels of vitamin B6 and its coenzyme were reassessed in relation to AST and ALT levels in patients undergoing long-term hemodialysis using high-performance liquid chromatography.

RESULTS

The mean (+/- SD) serum AST and ALT levels in 304 patients negative for hepatitis B surface antigen and anti-hepatitis C virus were 9.2 +/- 2.4 and 7.4 +/- 1.7 IU/L, respectively. In 556 normal adults, they were 22.7 +/- 5.4 and 18.0 +/- 4.0 IU/L, respectively (P < 0.001). Mean serum vitamin B6 and pyridoxal-5'-phosphate levels in patients undergoing dialysis were not reduced compared with the control, although occasionally patients had low levels. The AST and ALT assay reagents in Japan do not contain added pyridoxal-5'-phosphate; addition of pyridoxal-5'-phosphate (0.1 mmol/L) to the reagent significantly increased measurements to similar extents in both groups.

CONCLUSIONS

Serum AST and ALT levels in patients undergoing dialysis are very low, but they are not a result of vitamin B6 deficiency. The upper normal limits of AST and ALT levels in patients undergoing dialysis should be reduced considerably, and these levels should be interpreted with caution in the diagnosis of liver disease.

Micronutrition in dialysis

A variety of dialysis methods are currently used in the treatment of renal failure. Nutrition support modalities are also frequently used for patients with renal failure who are malnourished or at risk of becoming malnourished. The effects of various dialysis methods on certain micronutrient levels and needs have generally not been extensively studied, however, this article reviews information that has been published regarding carnitine, water soluble vitamin, fat soluble vitamin, and trace element levels during dialysis. Recommendations for provision of micronutrients during dialysis are provided.

Water soluble vitamins in chronic hemodialysis patients and need for supplementation

Forty-three patients on chronic hemodialysis who before the present study had only received a low-dose supplement of folic and ascorbic acid were studied prospectively for one year. After baseline values were obtained in month one, increasing doses of postdialysis vitamin supplements were prescribed for the vitamins which were found to be insufficient in order to determine the minimal amount of oral postdialysis supplement necessary to normalize vitamin levels. According to our results no systematic supplement was indicated for biotin, riboflavin or vitamin B12. For folic acid and vitamin C, supplementation with lower doses than those prescribed in many dialysis units allowed optimal vitamin levels in the majority of patients; 2 to 3 mg/week (300 to 400 micrograms/day) of folic acid and of 1000 to 1500 mg/week (150 to 200 mg/day) of vitamin C was considered sufficient. A severe pyridoxine deficiency was present in most (> 80%) unsupplemented patients, either as judged by pyridoxal-5-phosphate determinations in plasma or determination of specific enzyme activation in erythrocytes (EGOTo and alpha-EGOT); a postdialysis supplement of at least 100 to 150 mg/week of pyridoxine hydrochloride (> 15 to 20 mg/day) corrects this deficiency. The activity of the thiamine-dependent enzyme transketolase in erythrocytes (ETKo) was insufficient in 35% and marginal in 21% of the patients, while whole blood thiamine determined simultaneously in 10 of the ETKo-deficient patients was within the normal range. These results suggest that in uremia insufficient transketolase activity may be related to inhibition of the enzymatic system rather than to true vitamin deficiency. On a long-term basis a supplement of 200 to 300 mg/week of thiamine hydrochloride (30 to 45 mg/day) restored ETKo to satisfactory levels in most patients; whether this supplement is to be recommended warrants further studies.

Determinants of oxalate balance in patients on chronic peritoneal dialysis

We assessed plasma levels and removal rates of oxalate in 24 patients on chronic peritoneal dialysis (CPD) for oxalosis-unrelated renal failure. The ion-chromatographic (IC) measurements of oxalate in plasma, dialysate, and urine (in seven patients with residual renal function) were used to calculate peritoneal and renal clearances of oxalate. The serum state of saturation with calcium oxalate was calculated by means of a computer-based model system. Patient data were compared with those from 19 healthy individuals. Peritoneal clearance of oxalate was 6.3 +/- 4.7 mL/min, ie, 8% of the normal renal clearance. As a result, both plasma oxalate and calcium oxalate saturation were higher than in controls and did not overlap. Plasma was supersaturated with calcium oxalate in only two of 24 patients (8%). Removal of oxalate by dialysis was related to the amount of fluid infused. Overall removal of oxalate (dialysate plus urine) was similar to 24-hour excretion of normal subjects and was taken as a measure of its generation. Oxalate generation rate was dependent on protein (whole and animal) intake, but not on caloric intake or pyridoxine status. Pyridoxine supplementation, 75 and 300 mg daily for 1 months, was not effective in reducing plasma levels or generation rates of oxalate. Residual renal function had a minor influence on oxalate patterns. We conclude that current programs are adequate to maintain oxalate balance in patients on CPD under basic conditions.

Effects of ascorbic acid and pyridoxine supplementation on oxalate metabolism in peritoneal dialysis patients

We studied the effect of vitamin C and B6 supplementation on oxalate metabolism in seven patients receiving chronic peritoneal dialysis therapy. The study was divided into three phases, each lasting 4 weeks. Plasma oxalate, total ascorbic acid, and pyridoxal-5'-phosphate (PLP) were measured at the end of each phase. Twenty-four-hour urinary excretion and dialysate removal rates of oxalate were also obtained. At the end of phase I (supplement-free period), plasma oxalate levels were markedly elevated at 47.6 +/- 7.1 mumol/L (437 +/- 66 micrograms/dL) (normal, 3.4 +/- 0.4 mumol/L [30.3 +/- 1.6 micrograms/dL]). Plasma total ascorbic acid levels were 62 +/- 6 mumol/L (1.0 +/- 0.1 mg/dL) (normal, 45 to 57 mumol/L [0.8 to 1.0 mg/dL]), while plasma PLP levels were markedly reduced to 24 +/- 5 nmol/L (normal, 40 to 80 nmol/L). Daily supplements of 0.57 mmol (100 mg) ascorbic acid orally (phase II) resulted in a 19% increase in the plasma oxalate levels to 57.8 +/- 6.1 mumol/L (520 +/- 55 micrograms/dL) (P less than 0.03), with a concomitant 60% increase in the plasma ascorbate levels (91 +/- 6 mumol/L [1.6 +/- 0.1 mg/dL], P less than 0.01). Plasma PLP values remained low. Finally, during phase III (0.57 mmol or 100 mg ascorbic acid plus 59.6 mumol or 10 mg pyridoxine HCI orally daily), plasma oxalate levels declined by 17% to 47.9 +/- 5.2 mumol/L (431 +/- 47 micrograms/dL) (P greater than 0.05 v phase II).(ABSTRACT TRUNCATED AT 250 WORDS)

Vitamin B6 requirements in chronic renal failure

According to our results the long-term daily oral supplementation of 6 mg vitamin B6 was sufficient for prevention of vitamin B6 deficiency in chronic renal failure, regular dialysis treatment and CAPD groups of patients. Haemodialysis and charcoal haemoperfusion have led to non-significant decrease of erythrocyte vitamin B6. A favourable effect was found of daily oral administration of 50 mg pyridoxine on electrophoretic mobility of peripheral blood lymphocytes and cellular immunity.

Ascorbic acid supplements in patients receiving chronic peritoneal dialysis

Ascorbic acid supplements are commonly prescribed to patients with end-stage renal disease receiving peritoneal dialysis. To establish the need for ascorbic acid supplements, we evaluated seven chronic peritoneal dialysis patients during a supplement-free (phase I) period, and while receiving oral ascorbic acid (0.57 mmol/d [100 mg/d]) (phase II). Because of a proposed interaction with vitamin B6, patients were additionally supplemented with pyridoxine HCl (59.6 mumol/d [10 mg/d]) (phase III). Plasma levels and dialysate removal rates of total ascorbic acid and plasma pyridoxal-5-phosphate (PLP) were measured at the end of each phase. During phase I, plasma ascorbic acid levels (normal, 45 to 57 mumol/L [0.8 to 1.0 mg/dL]) declined slightly from 74 +/- 11 mumol/L (1.3 +/- 0.2 mg/dL) to 62 +/- 11 mumol/L (1.1 +/- 0.2 mg/dL) (P less than 0.02) at the end of the third week, and then remained stable to the end of the fourth week. Plasma ascorbic acid levels were no different in patients with or without residual renal function. With the addition of vitamin C supplements, plasma ascorbic acid levels increased by 45% of the baseline value at the end of phases II (P less than 0.001). The dialysate removal rate of ascorbic acid was 0.28 +/- 0.03 mmol/d (50 +/- 6 mg/d) at the end of phase I, and increased by 57% of the baseline value at the end of phases II (P less than 0.001). However, the peritoneal clearance of ascorbic acid remained unchanged during all phases the study. Pyridoxine depletion or repletion had no effect on plasma ascorbic acid levels (P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)