Table 1.
Studies on ascorbic acid concentration in serum or plasma of hemodialysis patients.
| Dialysis Modality (Study’s Country) |
Study Description | Main Results | References |
|---|---|---|---|
| Hemodialysis (Greece) |
Cross-sectional, 93 HD patients (aged 19–71 years, HD dose 12 h/week, HD vintage 10–137 months), 52 healthy controls, AA determination with the enzymatic method in pre-HD serum. |
HD patients presented 4-fold smaller mean AA concentration than healthy subjects, 12.0 ± 8.1 vs. 50.0 ± 22.1 μmol/L respectively. | Papastephanidis et al.(1987) [35] |
| Hemodiafiltration or hemodialysis (Austria) |
Cross-sectional, 130 HD/HDF patients (median: age 60, 74% on HDF, HD/HDF vintage 20 months, Kt/V 1.39). AA determination with the HPLC method in pre-HD plasma. |
Median AA concentration was 45.1 μmol/L, IQR: 24.3–76.1 μmol/L. | Deicher et al.(2004) [42] |
| Hemodialysis (NYC, USA) |
Cross-sectional, 117 HD patients (mean: age 63, HD vintage 3.2 years, HD dose unknown). AA determination with the HPLC in pre-HD plasma m |
Mean AA concentration was 58.9 ± 65.3 μmol/L. Values < 10 μmol/L, between 10 and 80 μmol/L and > 80 μmol/L observed in 15%, 66% and 19% percent of patients respectively. | Richter et al.(2008) [45] |
| Hemodialysis (China) |
Cross-sectional, 117 HD patients (mean: age 59, HD vintage 49 months, Kt/V 1.6) AA determination with the HPLC in pre-HD plasma m. |
AA concentration < 2 μg/mL **, between 2- 4 μg/mL and > 4 μg/mL was present in: 38%, 27% and 35% of patients respectively | Zhang et al. (2011) [46] |
| Conventional and extended hours hemodialysis (Australia) |
Cross-sectional, 26 patients in EHD (mean age: 55, HD vintage 25.7 months, HD dose 28 h/week) 26 in CHD (mean: age 71, HD vintage 57 months, HD dose 13.5 h/week). AA determination with HPLC in pre-HD serum. |
Median pre-HD AA concentration was 3.8-fold lower in the EHD than the CHD group (0.30 vs. 1.14 mg/dL *). | Coveney et al.(2011) [48] |
| Conventional and frequent hemodialysis (USA) |
Participants of the FHN trial, NCT00264758. CHD group: 20 patients, mean age 50.6, 3 HD sessions per week, median duration 3.5 h, Kt/V = 1.46. FHD group: 24 patients, mean age 48.8, 6 HD sessions per week, median duration 2.4 h, Kt/V = 1.43. AA determination with the HPLC in pre-HD plasma m. |
Mean AA concentration approximated 25 ± 22 μmol/L and did not differ between groups and time points. 25% of patients have AA concentration < 10 μmol/L. | Raimann et al. (2019) [47] |
* Conversion factor for units: vitamin C mg/dL to μmol/L × 56.78. ** Conversion factor for units: vitamin C μg/mL to μmol/L × 5.678. m Plasma stabilization with metaphosphoric acid. AA, Ascorbic Acid; CHD, Conventional hemodialysis; EHD, extended hemodialysis; FHD, frequent hemodialysis; HD, Hemodialysis; HDF, Hemodiafiltration; HPLC, High-performance liquid chromatography; IQR, interquartile range; Kt/V, parameter of dialysis dose.