- Open Access
Dosing adjuvant vitamin C in critically ill patients undergoing continuous renal replacement therapy: We are not there yet!
Critical Care volume 23, Article number: 5 (2019)
We read with great interest the recent letter to Critical Care by Marik and Hooper . Vitamin C (vit C) is increasingly recognized as a crucial compound to alleviate morbidity in critically ill patients. Vit C concentrations, however, are usually far below normal and even close to “scurvy levels” in this population. Vit C also is substantially cleared by continuous renal replacement therapy (CRRT). Significant vit C deficiency was observed in 80% of patients subjected to various types of CRRT despite receiving a daily intravenous (IV) supplement of 500 to 1000 mg . Therefore, high-dose (from 6 to 12 g) vit C substitution during CRRT seems justified .
Marik and Hooper argued against such dose increase in patients receiving CRRT. To support their statement, they provided serum vit C dosages in a small number of septic patients who received 6 g vit C IV while undergoing continuous veno-venous hemofiltration (CVVH). Vit C trough and peak levels were largely above normal and comparable to levels obtained in patients not receiving CVVH .
We want to warn against oversimplification. Marik and Hooper measured vit C within 30 min after the end of vit C infusion. It would have been more relevant to measure vit C after 24 to 48 h of CVVH treatment. Up to 50% of vit C is cleared in a time-dependent manner during a 4-h session of intermittent hemodialysis or hemodiafiltration [4, 5], which suggests that continuous techniques may exacerbate vit C losses. Vit C also is eliminated by both diffusion (dialysis) and convection (filtration). During hemodiafiltration, diffusion is responsible for two thirds of the vit C loss whereas convection accounts only for one third . CVVH is a sheer convective technique in contrast with other often-used CRRT modes in the critically ill, such as continuous veno-venous hemodialysis (CVVHD) and continuous veno-venous hemodiafiltration (CVVHDF). Marik and Hooper thus report the most modest way of CRRT-induced vit C elimination. It is reasonable to think that more diffusion-based CRRT techniques may yield other results.
We agree with Marik and Hooper that 6 g/day vit C IV is sufficient for patients without acute kidney injury and not requiring CRRT. However, vit C measurements should be performed after prolonged CVVH sessions to ensure that a 6 g daily supplement can keep levels within normal range. More studies are needed in patients receiving CVVHD or CVVHDF to exclude overlooking too great a vit C loss.
Continuous renal replacement therapy
Continuous veno-venous hemofiltration
Continuous veno-venous hemodialysis
Continuous veno-venous hemodiafiltration
- Vit C:
Marik PE, Hooper MH. Adjuvant Vitamin C in critically ill patients undergoing renal replacement therapy: What's the right dose? Crit Care. 2018;22:320. https://doi.org/10.1186/s13054-018-2190-y. No abstract available.
Kamel AY, Dave NJ, Zhao VM, Griffith DP, Connor MJ Jr, Ziegler TR. Micronutrient Alterations During Continuous Renal Replacement Therapy in Critically Ill Adults: A Retrospective Study. Nutr Clin Pract. 2018;33:439–46. https://doi.org/10.1177/0884533617716618 Epub 2017 Dec 18.
Honore PM, De Bels D, Preseau T, Redant S, Attou R, Spapen HD. Adjuvant vitamin C in cardiac arrest patients undergoing renal replacement therapy: an appeal for a higher high-dose. Crit Care. 2018;22:207. https://doi.org/10.1186/s13054-018-2115-9.
Fehrman-Ekholm I, Lotsander A, Logan K, Dunge D, Odar-Cederlöf I, Kallner A. Concentrations of vitamin C, vitamin B12 and folic acid in patients treated with hemodialysis and on-line hemodiafiltration or hemofiltration. Scand J Urol Nephrol. 2008;42:74–80. https://doi.org/10.1080/00365590701514266.
Morena M, Cristol JP, Bosc JY, Tetta C, Forret G, Leger CL, et al. Convective and diffusive losses of vitamin C during haemodiafiltration session: a contributive factor to oxidative stress in haemodialysis patients. Nephrol Dial Transplant. 2002;17:422–7.
Availability of data and materials
Ethics approval and consent to participate
Consent for publication
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
See related letter by Marik and Hooper https://ccforum.biomedcentral.com/articles/10.1186/s13054-018-2190-y.
About this article
Cite this article
Honore, P.M., De Bels, D., Kugener, L. et al. Dosing adjuvant vitamin C in critically ill patients undergoing continuous renal replacement therapy: We are not there yet!. Crit Care 23, 5 (2019). https://doi.org/10.1186/s13054-018-2297-1