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Thursday, 2 September 2021

 

Measuring vitamin C in critically ill patients: clinical importance and practical difficulties—Is it time for a surrogate marker?

 

by Sander Rozemeijer, Frans A. L. van der Horst and Angélique M. E. de Man 

 

Critical Care volume 25, Article number: 310 (2021) Published: 31 August 2021

Interest in intravenous vitamin C administration has rapidly increased in the field of critical care medicine over recent years. The first studies investigating the effect of intravenous vitamin C in septic (shock) patients showed a decrease in organ dysfunction, vasopressor dependency, and even a reduction in mortality [1,2,3]. Within a short period of time, multiple trials in septic patients were conducted to confirm these promising findings, but results were not uniform [4,5,6,7,8,9,10,11,12]. The inconsistencies in effects on outcome may partially be explained by differences in study design [8], in particular the dosing regimens (timing, duration and dose) and choice of co-medication. For example, vitamin C administration has been investigated alone, or in combination with thiamine and/or hydrocortisone, sometimes with uncontrolled use of hydrocortisone in the control group. There is also considerable variety among septic patients as sepsis is a heterogeneous syndrome. Therefore, some subgroups of patients might benefit more than others from intravenous vitamin C therapy. A recently published meta-analysis on mortality performed subgroup analyses and found a beneficial effect of vitamin C on short-term mortality (< 30 days). Additionally, survival was improved by a treatment duration of 3–4 days [13]. The results of vitamin C alone versus combination therapy were not different. A particular subgroup of interest is patients with vitamin C deficiency. None of the studies performed subgroup analyses on vitamin C deficient patients. This is unfortunate, but understandable, since the measurement of plasma vitamin C concentration is difficult.

In this chapter, we discuss the practical problems and pitfalls of measuring vitamin C and describe a novel potential surrogate marker that can estimate vitamin C status.

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