Porth's Essentials of Pathophysiology, 4e

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Integrative Body Functions

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tissue wasting, in which the tumor induces metabolic changes leading to a loss of adipose tissue and muscle mass. 45 In healthy adults, body protein homeostasis is main- tained by a cycle in which the net loss of protein in the postabsorptive state is matched by a net postprandial gain of protein. 46 In persons with severe injury or ill- ness, net protein breakdown is accelerated and pro- tein rebuilding disrupted. Protein mass is lost from the liver, gastrointestinal tract, kidneys, and heart. As pro- tein is lost from the liver, hepatic synthesis of proteins declines, and plasma protein levels decrease. There also is a decrease in immune cells. Wound healing is poor, and the body is unable to fight off infection because of multiple immunologic malfunctions throughout the body. The gastrointestinal tract undergoes mucosal atrophy with loss of villi in the small intestine, result- ing in malabsorption. The loss of protein from cardiac muscle leads to a decrease in myocardial contractility and cardiac output. The muscles used for breathing become weakened, and respiratory function becomes compromised as muscle proteins are used as a fuel source. A reduction in respiratory function has many implications, especially for persons with burns, trauma, infection, or chronic respiratory disease and for persons who are being mechanically ventilated because of respi- ratory failure. In hospitalized patients, malnutrition increases mor- bidity and mortality rates, incidence of complications, and length of stay. Malnutrition may present at the time of admission or develop during hospitalization. The hospitalized patient often finds eating a healthy diet difficult and commonly has restrictions on food and water intake in preparation for tests and surgery. Pain, medications, special diets, and stress can decrease appetite. Even when the patient is well enough to eat, being alone in a room where unpleasant treatments may be given is not conducive to eating. Although hospital- ized patients may appear to need fewer calories because they are on bed rest, their actual need for caloric intake may be higher because of other energy expenditures. For example, more calories are expended during fever, when the metabolic rate is increased. There also may be an increased need for protein to support tissue repair after trauma or surgery. Diagnosis No single diagnostic measure is sufficiently accurate to serve as a reliable test for malnutrition. Techniques of nutritional assessment include evaluation of dietary intake, anthropometric measurements, clinical exami- nation, and laboratory tests. 44 Evaluation of weight is particularly important. Body weight can be assessed in relation to height using the BMI. Evaluation of body composition can be performed by inspection or using anthropometric measurements such as skinfold thick- ness. Serum albumin and prealbumin are used in the diagnosis of protein-calorie malnutrition. Albumin, which has historically been used as a determinant of nutrition status, has a relatively large body pool and a

half-life of 20 days and is less sensitive to changes in nutrition than prealbumin, which has a shorter half-life and a relatively small body pool. 44 Treatment The treatment of severe protein-calorie malnutrition involves the use of measures to correct fluid and elec- trolyte abnormalities and replenish proteins, calories, and micronutrients. 44 Treatment is started with modest quantities of proteins and calories based on the person’s actual weight. Concurrent administration of vitamins and minerals is needed. Either the enteral or parenteral route can be used. The treatment should be undertaken slowly to avoid complications. The administration of water and sodium with carbohydrates can overload a heart that has been weakened by malnutrition and result in congestive failure. Enteral feedings can result in mal- absorptive symptoms due to abnormalities in the gastro- intestinal tract. Refeeding edema is a benign dependent edema that results from renal sodium reabsorption and poor skin and blood vessel integrity. It is treated by elevation of the dependent area and modest sodium restrictions. Diuretics are ineffective and may aggravate electrolyte deficiencies. Eating Disorders Eating disorders, which include anorexia nervosa, buli- mia nervosa, and binge-eating disorder and their vari- ants to result from serious disturbances in eating, such as restriction of intake and binging, with an excessive concern over body shape or body weight. 47–50 Eating disorders typically occur in adolescent girls and young women, although 10% of cases of anorexia nervosa and bulimia nervosa occur in boys and men. 51 Binge-eating disorder is more prevalent in men than anorexia nervosa and bulimia combined. Compared with women, men tend to experience less pressure to engage in behaviors such as self-induced vomiting or laxative use when over- eating, less of a sense of loss of control when binge eat- ing, and a greater tendency to use compulsive exercise rather than purging for weight control. 51 Eating disorders are more prevalent in industrial- ized societies and occur in all socioeconomic and major ethnic groups. A combination of genetic, neurochemi- cal, developmental, and sociocultural factors is thought to contribute to the development of the disorders. 47,48 The American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) has established criteria for the diagnosis of anorexia nervosa, bulimia nervosa, and binge-eating disorder. 52 Although these criteria allow clinicians to make a diagnosis in persons with a specific eating dis- order, the symptoms often occur along a continuum between those of anorexia nervosa and bulimia nervosa. Preoccupation with weight and excessive self-evaluation of weight and shape are common to both disorders, and persons with eating disorders may demonstrate a mix- ture of both disorders. 48 The female athlete triad, which includes low energy availability, menstrual dysfunction,