Where's the Protein?
This stress results in numerous changes in the body. The inflammatory response-the body's protective mechanism during times of stress-causes the body to alter blood flow to the injury or infection site. At the same time, the metabolic rate increases (hypermetabolism) to mobilize nutrients into glucose and amino acid pools. In severe stress, the body uses glycogen stores and protein to make glucose and stress factors (such as the cytokines interleukin-1, interleukin-6, and tumor necrosis factor). Hormonal changes during stress shift the balance between insulin and the counter regulatory hormones (including catecholamines, cortisol, and glucagon). Insulin assists carbohydrate and lipid storage and protein synthesis. But during stress, the rise of the counterregulatory hormones is greater than the rise in insulin. Metabolic and total energy rates increase as the patient's body continues to deplete protein stores.
Hormonal changes also occur in severe stress, resulting in increased glycogen breakdown and mobilization of free fatty acids. Glucagon breakdown increases and accelerates glucose production from amino acids. As this continues, storage of glucose, fatty acids, and protein declines. Protein from the skeletal muscle, connective tissue, and the gastrointestinal tract is converted to provide the glucose and amino acids needed to support the synthesis of stress factors and immune cells1Figure 1.
Cytokines-cell-mediated proteins-enhance the immune defenses by stimulating production of cells to attack foreign organisms; however, these cytokines can also cause fever and anorexia.2 The increase in cytokines accelerates protein breakdown or catabolism as well2,3Figure 2. In addition, fat metabolism increases and plasma levels of the essential fatty acids (linoleic [omega-6 fatty acid] and linolenic [omega-3 fatty acid]) decrease. Some studies show that clinical signs of fatty acid depletion can develop in 10 days.4 Cells in the intestinal tract may also shrink and lose some of their absorptive ability and immune function as the protein in the gastrointestinal tract is used in response to stress.
These physiologic changes are seen in patients every day, particularly in the long-term-care setting. The following case study illustrates the issues and suggests options for managing these patients.