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The paper by Sheikh and Horner  does not properly describe the context for vitamin C.
Fourteen trials have investigated the effect of vitamin C against post-operative AF (POAF), and significant heterogeneity has appeared between studies carried out in the USA and outside of the USA . In 9 non-US studies vitamin C decreased the incidence of POAF on average by 46% (P<0.00001), but no benefit was seen in 5 US studies.
In 5 non-US studies, intravenous vitamin C shortened the duration of hospital stay on average by 16% and by 1.47 days (P<0.00001). In 7 non-US studies, oral and intravenous vitamin C shortened the duration of ICU stay on average by 7% (P=0.002). Thus, there is strong evidence from randomized trials indicating that vitamin C may influence the duration of hospital stay and ICU stay in some contexts. It is not reasonable to restrict to mortality as the only outcome of interest , when considering potential effects of vitamin C on ICU patients.
Sheikh and Horner do not mention that sometimes vitamin C levels are very low in hospital patients. For example, in one study 18 patients with clinical symptoms of scurvy were identified out of 145 consecutive patients . Scurvy has been reported also in modern ICUs .
In their clinical scenario, Sheikh and Horner described a patient with pneumonia, but ignored the association between vitamin C and pneumonia. Vitamin C deficiency increases the risk of pneumonia, and pneumonia d...
In their clinical scenario, Sheikh and Horner described a patient with pneumonia, but ignored the association between vitamin C and pneumonia. Vitamin C deficiency increases the risk of pneumonia, and pneumonia decreases vitamin C levels in the body [5-7]. Thus, it would be unscientific to argue that the vitamin C level of a pneumonia patient is an uninteresting issue.
I agree with Sheikh and Horner that further trials are required to investigate the role of vitamin C in sepsis . However, while waiting for such trials, it is reasonable to measure vitamin C levels of ICU patients and administer vitamin C to those who have low levels.