1. Luisa Sandri, MD, and Martino Marangella, MD
Long-Term, Low-Dose, Intravenous Vitamin C Leads to Plasma Calcium Oxalate Supersaturation in Hemodialysis Patients
Caterina Canavese, MD, Michele Petrarulo, PhD, Paola Massarenti, PhD, Silvia Berutti, MD,
Roberta Fenoglio, MD, Daniela Pauletto, PhD, Giacomo Lanfranco, PhD, Daniela Bergamo, MD,
Luisa Sandri, MD, and Martino Marangella, MD
American Journal of Kidney Diseases
Vol 45, No 3 (March), 2005: pp

2. BACKGROUND Vitamin C Antioxidant component RDT Pt. supplementation
(Ascorbic acid )
Hyperoxalemia
Supersaturation-ca oxalate
Iron deficiency patients
Epo. Effect

3. BACKGROUND Long term vit.C intravenous supplyment on RDT
: mg 3times weekly
Safety concerns for secondary hyperoxalemia
Lowest dosage accomplish stable normal plasma ascorbate levels

4. METHODS STUDY DESIGN Prospective study
250mg ( 1.42 mmol ) iv once a week  priming phase of 3 months
500mg iv once a week  second priming phase of 3 months , maintenance phase of 12 months
Plasma ascorbate and oxalate level monthly check
Intradialytic balance study

5. METHODS STUDY GROUP Reference Untreated Patients 40 patients on RDT
18 patients selected  serum ascorbate low-end range of normal values ( 2.6 mg/L )
Ascorbate dietary intake mg/d at the beginning of the study , no interventional change
Reference Untreated Patients
56 patients on long-term dialysis therapy
12 patients selected  serum ascorbate and oxalate levels at baseline , absence of vit.C supplement

6. METHODS Sampling and Analytical Procedures Calculations
Blood sampling  start and end of the same dialysis session in iv ascorbate
Ion chromatography and reverse-phase high-performance liquid chromatography
Calculations
plasma supersaturation with respect to calcium oxalate ( bCaOx ) inito computer calculation

7. RESULTS

8. Fig 1. Predialysis plasma ascorbate level profiles during the entire study.
Shaded
areas on the bottom denote
ascorbate dosages. Means
SD are shown. To convert
ascorbate in mg/L to mol/L,
divide by *P < 0.01
versus baseline values. **P
< versus baseline values.

9. Fig 2. Predialysis plasma oxalate level profiles during the entire study.
Shaded areas on the bottom
denote ascorbate dosages. Means
SD are shown. To convert oxalate
in mg/L to mol/L, divide
by *P < 0.01 versus
baseline. **P < 0.001
versus baseline. §P < 0.01
versus ascorbate, 500 mg/wk.

10. Fig 3. Changes in predialysis plasma oxalate levels during the entire study in individual patients.
The shaded area denotes undersaturation.
Samples with oxalate
plasma levels exceeding the saturation line increased at
greater dosages of supplemental
ascorbate. To convert
oxalate in mg/L to mol/L, divideby

11. Table 1. Number of Samples Supersaturated With Calcium Oxalate

12. Table 2. Plasma Levels and Dialysis Removal ofAscorbate and Oxalate Before and After Ascorbate Supplementation at Different Dosages

13. Table 3. Predialysis Plasma Ascorbate and Oxalate Levels in the Reference Untreated Group Assessed in 2 Different Settings Without Ascorbate Supplementation

14. Conclusion RDT ( regular dialysis treatment ) patient
 Recommend long-term intravenous supplementation of mg/weekend
Significant risk for oxalate supersaturation
 oxalate measurement are strongly recommended