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Background: Ascorbate supplementation for patients on regular dialysis treatment (RDT) is advised to obviate deficiency and improve epoetin response in those with functional iron deficiency. However, clear-cut safety concerns regarding hyperoxalemia are still poorly understood. This study tries to establish safety/efficacy profiles of ascorbate and oxalate during long-term intravenous ascorbate supplementation., Methods: A prospective study was performed in 30 patients on RDT showing ascorbate deficiency (plasma ascorbate < 2.6 mg/L [<15 micromol/L]): 18 patients were administered intravenous ascorbate during 18 months (250 mg/wk, subsequently increased to 500 mg), and 12 patients were taken as reference untreated cases. Plasma ascorbate and oxalate assays and dialytic balance determinations were performed (ion chromatography and reverse-phase high-performance liquid chromatography, respectively) at baseline, during treatment, and 12 months after withdrawal., Results: Plasma ascorbate levels increased dose dependently with supplementation (1.6 +/- 0.8 mg/L [9.1 +/- 4.6 mumol/L] at baseline, 2.8 +/- 1.8 mg/L [15.9 +/- 10.1 micromol/L]) with 250 mg of ascorbate, and 6.6 +/- 2.8 mg/L [37.5 +/- 16.0 micromol/L] with 500 mg/wk of ascorbate), but only normalized with greater dosages for several months in 94% of patients. Baseline plasma oxalate levels increased from 3.2 +/- 0.8 mg/L (35.8 +/- 8.8 micromol/L) to 3.6 +/- 0.8 mg/L (39.5 +/- 9.1 micromol/L) and 4.5 +/- 0.9 mg/L (50.3 +/- 10.4 micromol/L) with 250 and 500 mg, respectively ( P < 0.001). The calcium oxalate saturation threshold was exceeded by 7 of 18 patients (40%) during 6 months therapy with 500 mg/wk. Ascorbate dialysis removal increased from 37.8 +/- 23.2 mg (215 +/- 132 micromol) to 99.6 +/- 51.7 mg (566 +/- 294 micromol) during supplementation (P < 0.001), with corresponding increases in oxalate removal from 82.5 +/- 33.2 mg (917 +/- 369 micromol) to 111.2 +/- 32.6 mg/L (1,236 +/- 362 micromol; P < 0.01). Withdrawal reverted plasma levels and dialysis removal to initial values. Values for untreated patients did not change during 1 year of follow-up., Conclusion: Patients on RDT may resolve ascorbate deficiency with intravenous supplementation of 500 mg/wk, but this implies a significant risk for oxalate supersaturation. Oxalate measurements are strongly recommended during long-term ascorbate therapy.

OBJECTIVE To investigate metabolic disturbances, possibly leading to stone disease, in the Camey II technique for creating a urinary reservoir from an intestinal segment. PATIENTS, SUBJECTS AND METHODS Thirty patients with a Camey II ileal neobladder and 26 controls had metabolic investigations of blood samples, and 24-h and fasting urine samples, to assess renal function, the risk of stone formation, and bone turnover. The state of saturation with calcium oxalate, uric acid and brushite were calculated using a computer program. RESULTS The patients had lower renal clearances than the controls ( P < 0.001), with a slight tendency to decrease with time from surgery. Metabolic hyperchloraemic acidosis occurred in 57% of the patients and tended to be worse at lower glomerular filtration rates ( P < 0.05). Severe hypocitraturia in both daily and fasting urine was the most striking urinary feature. There was no difference in the other variables. The state of saturation with brushite was slightly higher in patients due to the slightly higher urinary pH. There was a trend to lower bone turnover, involving markers of both resorption and formation, in the patients. CONCLUSIONS The Camey II technique led to only minor functional or metabolic changes; renal function tended to deteriorate and mild metabolic acidosis was the main feature. Fasting and 24-h hypocitraturia occurred in most patients, representing a potential threat for calcium stone formation. [ABSTRACT FROM AUTHOR]