Trace elements: Clinical perspectives in the critically ill.

Trace elements are required in minute quantities in the diet but play a vital role in a wide variety of functions, such as co-factors in antioxidant reactions and normal immune function to DNA and protein synthesis and skeletal and tissue remodelling and repair. Critically ill patients are at risk of trace element deficiency or excess, due to changes in intake, absorption, metabolism or excretion. Deficiency or excess can lead to a wide range of cellular and organ dysfunction that may be seen in patients with an acute or critical illness, including cardiomyopathy, impaired glucose tolerance and reduced oxygen delivery. In addition, various diseases, such as systemic inflammation and renal and intestinal failure, and intensive care treatments, such as parenteral nutrition, renal replacement therapy and diuretics, can increase the likelihood of deficient or excessive amounts of micronutrient levels. This narrative review discusses sources and normal physiology of trace element handling and how this may be impaired in critically ill patients. It then discusses various conditions seen in critically ill patients that may be caused or exacerbated by abnormal trace element status and the current evidence around whether supplementation is of benefit in particular critical illnesses.