Vitamin C is an essential water-soluble nutrient which cannot be synthesised or stored by humans. It is a potent antioxidant with anti-inflammatory and immune-supportive roles. Previous research has indicated that vitamin C levels are depleted in critically ill patients. In this study we have assessed plasma vitamin C concentrations in critically ill patients relative to infection status (septic shock or non-septic) and level of inflammation (C-reactive protein concentrations). Vitamin C status was also assessed relative to daily enteral and parenteral intakes to determine if standard intensive care unit (ICU) nutritional support is adequate to meet the
vitamin C needs of critically ill patients.
Forty-four critically ill patients (24 with septic shock, 17 non-septic, 3 uncategorised) were recruited from the Christchurch Hospital Intensive Care Unit. We measured concentrations of plasma vitamin C and a proinflammatory biomarker (C-reactive protein) daily over 4 days and calculated patients’ daily vitamin C intake from the enteral or total parenteral nutrition they received. We compared plasma vitamin C and C-reactive protein concentrations between septic shock and non-septic patients over 4 days using a mixed effects statistical model, and we compared the vitamin C status of the critically ill patients with known vitamin C bioavailability data using a
four-parameter log-logistic response model.
Overall, the critically ill patients exhibited hypovitaminosis C (i.e., < 23 ?mol/L), with a mean plasma vitamin C concentration of 17.8 ± 8.7 ?mol/L; of these, one-third had vitamin C deficiency (i.e., < 11 ?mol/L). Patients with hypovitaminosis C had elevated inflammation (C-reactive protein levels; P < 0.05). The patients with septic shock had lower vitamin C concentrations and higher C-reactive protein concentrations than the non-septic patients (P < 0.05). Nearly 40% of the septic shock patients were deficient in vitamin C, compared with 25% of the non-septic patients. These low vitamin C levels were apparent despite receiving recommended intakes via enteral and/or parenteral nutritional therapy (mean 125 mg/d).
Critically ill patients have low vitamin C concentrations despite receiving standard ICU nutrition. Septic shock patients have significantly depleted vitamin C levels compared with non-septic patients, likely resulting from increased metabolism due to the enhanced inflammatory response observed in septic shock.
This study demonstrates that ALL critically ill patients are vitamin C deficient; It should be noted that this finding has been known for over 20 years. In addition, the study by Carr et al demonstrated that 40% of patients with septic shock had vitamin C levels diagnostic of biochemical SCURVY. Furthermore, low serum levels are associated with severe cellular deficiency. In critically ill patients, vitamin C levels have been inversely associated with disease severity and the risk of organ failure and death. The likely cause of the vitamin C deficient is metabolic consumption. Considering the role of Vitamin C plays in a multitude of biochemical reactions and pathways relevant to sepsis, these findings provide a strong rationale for treating all septic patients with intravenous vitamin C.
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