Most patients having major surgery do not experience serious malnutrition. However, the disease process or metabolic response to recent major surgery, trauma, burns, or severe acute infection can increase the risk of malnutrition and affect subsequent nutrient requirements for rehabilitation and recovery (Souba and Wilmore, 1994). The variability in the metabolic and physiologic responses to major surgery, trauma, burns, and severe acute infections is related in part to the patient's age, previous state of health, preexisting disease, previous stress, and specific pathogens.
Data on the prevalence of recent major surgery, trauma, burns, or severe acute infections among women, infants, and children in the U.S. population or participating in the WIC program were not available to the committee. Chronic and recurrent infections and HIV infection are discussed in previous sections of this chapter.
The catabolic response to surgery occurs as a result of the traumatic insult of surgery and other complications of both preexisting disease and gastrointestinal function that diminish food intake (Souba and Wilmore, 1994). Persons experiencing severe trauma such as automobile accidents or burns exhibit a hypermetabolic state that may reach twice the basal levels and persist for 2 months or longer (Wilmore, 1977). Alterations in the metabolism of glucose, protein, and fat occur following injury. There is a marked rise in the regulatory hormones (glucagon, glucocorticoids, and catecholamines) in all phases of injury or after severe burn.
The gut functions as a central organ of amino acid metabolism, a role that becomes more pronounced during a critical illness. Disuse of the gastrointestinal tract during major illnesses may lead to numerous physiologic derangements, changes in the microflora, impaired immune function in the gut, and disruption of the integrity of the mucosal barrier.
Severe infections are characterized by prolonged fever, hypermetabolism, diminished protein economy, altered glucose dynamics, and accelerated lipolysis. Anorexia associated with severe infections contributes to the loss of lean body mass. Multiorgan and system involvement surrounding surgery, trauma, or