The body needs a certain amount of nutrients to maintain a constant, healthy state. This need is determined by the basal metabolic rate. Any external or internal trauma raises the metabolic rate, and greater amounts of oxygen and nutrients are required to supply enough fuel and amino acids for repair and recovery.
Energy expenditure may rise by 10 percent to 50 percent to support the intense metabolic workload (Omerbegovic M et al 2003). Protein and amino acid requirements increase to support formation of new tissues and proliferation of immune cells, maintain lean body mass (or muscle protein), and replace the protein lost to perspiration, bleeding, and excretion.
A positive nutritional balance is reflected in rapid healing of wounds, an efficient immune response, the absence of infections or sepsis (shock), and maintenance of a lean body mass.
Population studies indicate that 9 percent to 44 percent of people with wound and surgical trauma are malnourished (Reid CL 2004). The condition often goes unrecognized and untreated in hospitals, and some studies have explored the increased risk of malnutrition during hospital stays, based on the common occurrence of clinically significant weight loss observed in hospitalized surgical patients (Fettes SB et al 2002).
Biologically, it is difficult to achieve usual levels of nutrition after major trauma because many important nutrients are channeled into the healing effort. In addition, many trauma patients suffer from altered levels of consciousness, poor appetite, reduced digestive function, compromised blood circulation, and a radical alteration of normal daily routines.
There are also pronounced changes in the way the body metabolizes nutrients and food. Under normal circumstances, carbohydrates and fat are used to produce or store energy, and protein is used for developing and maintaining lean body mass. In this nonstressed condition, 90 percent of energy is supplied by carbohydrates or fat, and proteins contribute only 5 percent to 8 percent of total calories.
By contrast, during trauma, proteins, including muscle mass, are broken down to yield as much as 30 percent of caloric needs. Even when nutrients are supplemented, proteins will be utilized to provide 20 percent to 25 percent of caloric needs.
Compared to fat, protein yields less energy per gram. The patient becomes hypermetabolic, requiring higher-than-normal levels of calories and protein. The abnormal metabolism is caused by the release of stress hormones such as cortisol and catecholamines. This hypermetabolic state contributes to rapid loss of lean body mass, even when the patient is well fed. It is critical that trauma patients maintain an adequate supply of protein and calories to protect their lean muscle mass and supply their healing body with necessary nutrients.