Trace Elements in Critically Ill Patients Effects and Side Effects

Abstract

Nutrition is one of the most powerful but neglected weapon in critical care practice. Critically ill patients requiring vital organ support in the intensive care unit (ICU) commonly have anorexia and may be unable to feed volitionally by mouth for periods ranging from days to months. Unless such patients are provided with macronutrients in the form of enteral or parenteral nutrition, they accumulate an energy deficit that rapidly reaches proportions that contribute to lean-tissue wasting and that are associated with adverse outcomes. The catabolic response to acute critical illness is much more pronounced than that evoked by fasting in healthy persons, since the energy deficit in acutely ill patients is often superimposed on immobilization and pronounced inflammatory and endocrine stress responses. Severe skeletal-muscle wasting and weakness occurring during critical illness are associated with a prolonged need for mechanical ventilation and rehabilitation. In many studies, the degree of energy deficit accumulating in critically ill patients is strongly associated with the duration of stay in the ICU, which, in turn, is associated with an increased incidence of infectious complications and risk of death. Until recently, however, the causality of these associations remained unclear, since the majority of studies that formed the basis of published recommendations for feeding ICU patients were either observational or small interventional studies. Recently, the field of critical care nutrition has been revived by the findings of several randomized, controlled trials, which have opened a new debate on nutritional practice in the ICU. Parenteral and enteral nutrition is no longer considered merely adjunctive or supportive in the management of critically ill patients. Nutritional pharmacotherapy is, rather, a primary intervention providing protein, calories, and micronutrients to meet each patient’s dynamic metabolic needs and modulate disease processes. Micronutrients include the vitamins and minerals that are no less important than protein and calories to patient outcomes. Minerals are further differentiated as macrominerals and microminerals. Microminerals, or trace elements, are inorganic nutrients found in small quantities in the human body. The usual daily requirements of these minerals are in the milligram (mg) or microgram (g) range. At least a dozen trace minerals are thought to be essential to biologic function, although dietary requirements have only been established for 9. There are currently 6 trace elements available for routine parenteral use: chromium, copper, manganese, selenium, zinc and iron. The available literature on trace element nutrition has lead to the development of guidelines for monitoring and treatment for long-term adult patients who rely on PN. These guidelines are based on the limited literature available and clinical experience. Information about products, parenteral requirements and dosages, the risks and symptoms of deficiencies and toxicities, and the usefulness of laboratory tests can help to optimize care for patients who rely on long-term PN.