Nutritional assessment and support during infection.

Protein malnutrition is one of the principal factors relating to morbidity and mortality during infection. Nutritional assessment is required to determine the severity of depletion and degree of hypermetabolism affecting this patient population. Simple anthropometric and 24-hr urine collections together with routine biochemical analyses can readily allow clinical assessment to occur. Optimal utilization of dietary intake is dependent on the degree of protein catabolism and energy expenditure in excess of the basal energy requirement. Urinary nitrogen excretion in 24-hr on a protein-free diet is especially valuable in aiding this assessment. This analysis together with urinary creatinine which provide important estimates of lean body mass and serial measures will allow estimates of the progression of malnutrition. In infected adults optimal protein intake to produce positive nitrogen balance is 1.5 to 2.0 g of protein/kg per day. This would appear to reflect the fact that 16% of the caloric expenditure comes from protein sources during injury. Since this value is approximately twice that seen during nonstress, the reutilization of body protein would appear to be decreased. Careful appreciation of the metabolic response during infection is necessary prior to consideration of the nutritional support plan. Knowledge regarding the phase of infection, severity of nutritional depletion, and degree of hypermetabolism will influence the attainable goals of nutritional support.