Correction: Hill, A.; et al. Effects of Vitamin C on Organ Function in Cardiac Surgery Patients: A Systematic Review and Meta-Analysis. Nutrients 2019, 11, 2103

What do we know about micronutrients in critically ill patients? A narrative review

Micronutrient (MN) status alterations (both depletion and deficiency) are associated with several complications and worse outcomes in critically ill patients. On the other side of the spectrum, improving MN status has been shown to be a potential co-adjuvant therapy. This review aims to collect existing data to better guide research in the critical care setting. This narrative review was conducted by the European Society of Intensive Care Medicine Feeding, Rehabilitation, Endocrinology, and Metabolism MN group. The primary objective was to identify studies focusing on individual MNs in critically ill patients, selecting the MNs that appear to be most relevant and most frequently investigated in the last decade: A, B1, B2, B3, B6, folate, C, D, E, copper, iron, selenium, zinc, and carnitine. Given the limited number of interventional studies for most MNs, observational studies were included. For each selected MN, the review summarizes the main form and functions, special needs and risk factors, optimal treatment strategies, pharmacological dosing, and clinical implications all specific to critically ill patients. A rigorous rebalancing of research strategies and priorities is needed to improve clinical practice. An important finding is that high-dose monotherapy of MNs is not recommended. Basal daily needs must be provided, with higher doses in diseases with known higher needs, and identified deficiencies treated. Finally, the review provides a list of ongoing trials on MNs in critically ill patients and identifies a priority list of future research topics.

[Vitamin C and D supplementation in critically ill patients]

Micronutrient supplementation as part of the medical nutrition therapy for critically ill patients has received much attention in the past few years. Nevertheless, in clinical practice uncertainty remains about the optimal supplementation strategy, including which substance at which dosage should be administered at what time to specific groups of patients. Thus, the aim of this narrative review is to summarize the current evidence and recommendations for the micronutrients vitamin C and vitamin D. The physiological and pathophysiological roles of both vitamins are presented, recently published clinical trials are discussed, and the recommendations of the current guidelines are summarized. In addition, pragmatic tips for use in everyday clinical practice in the intensive care unit are given.

History of scurvy and use of vitamin C in critical illness: A narrative review

In 1747, an important milestone in the history of clinical research was set, as the Scottish surgeon James Lind conducted the first randomized controlled trial. Lind was interested in scurvy, a severe vitamin C deficiency which caused the death of thousands of British seamen. He found that a dietary intervention with oranges and lemons, which are rich in vitamin C by nature, was effective to recover from scurvy. Because of its antioxidative properties and involvement in many biochemical processes, the essential micronutrient vitamin C plays a key role in the human biology. Moreover, the use of vitamin C in critical illness-a condition also resulting in death of thousands in the 21st century-has gained increasing interest, as it may restore vascular responsiveness to vasoactive agents, ameliorate microcirculatory blood flow, preserve endothelial barriers, augment bacterial defense, and prevent apoptosis. Because of its redox potential and powerful antioxidant capacity, vitamin C represents an inexpensive and safe antioxidant, with the potential to modify the inflammatory cascade and improve clinical outcomes of critically ill patients. This narrative review aims to update and provide an overview on the role of vitamin C in the human biology and in critically ill patients, and to summarize current evidence on the use of vitamin C in diverse populations of critically ill patients, in specific focusing on patients with sepsis and coronavirus disease 2019.