Nutritional Assessment and Requirements
As with accidental injury, the onset of sepsis is generally sudden and unplanned. On the other hand, in contrast to trauma victims who are well nourished and healthy prior to their injury, infected patients are often nutritionally depleted when bacteremia develops. Malnutrition is inseparable from the occurrence and effects of infectious diseases, and their interaction is synergistic.
Assessment of patients with sepsis should start with a medical history and physical examination, which is frequently difficult because of the severity of the patient's illness. Use of anthropometric measurements is helpful, but weight may be an inaccurate reflection of nutritional status because of fluid retention. Serum protein concentrations (albumin and transferrin) are low because of redistribution secondary to the infection; hence these values are not useful indicators of malnutrition.
The immediate goal of nutritional therapy is weight maintenance. Weight gain and anabolism are generally difficult to achieve during the septic process, but they do occur once the disease process has abated. Total energy requirements can be calculated using the stress equation; mild-to-moderate infections increase energy requirements 20 to 30%, and severe infection increases caloric needs about 50% above basal levels. The optimal calorie:nitrogen ratio is approximately 150:1, although providing more nitrogen has been proposed.
Prompt initiation of nutritional support in patients with sepsis who cannot eat enough or should not eat is mandatory. On the other hand, provision of nutrients requires integration into the patients' management and support plan. The patient in the case example was started gradually on nutritional feedings, to avoid untoward complications of hyperglycemia, and the infusion was diminished during the second septic interval. Fat should compose a moderate proportion of the infused energy, to avoid the complications of hyperglycemia and to diminish the possibility of increased carbon dioxide production complicating hypercaloric glucose infusions. Severe erosion of lean body mass is possible in such a patient, and nutritional support helps to diminish such erosion. Provision of calories and nitrogen cannot attenuate the hypermetabolism characteristic of sepsis, but it does reduce accelerated catabolism.