The Absence of Protein -sparing Effects Utilizing Crystalline Amino Acids in Stressed Patients

Abstract

The protein-sparing effects of the peripheral infusion of crystalline amino acids (PAA) was studied metabolically in selected surgical patients subjected to various degrees of stress. Twenty-one patients (sixteen cancer patients receiving chemotherapy and/or radiotherapy, three with major abdominal traumatic injuries and four with paralytic ileus) were infused with 2 1/24 hours of a solution of 4.2% Travasol amino acids with only 5% glucose as a source of nonprotein calories. One-half of the cancer patients were also allowed ad libitum oral intake of a regular hospital diet or Vivonex-HN. The nutritional status was evaluated by measuring changes in body weight, serum albumin levels and nitrogen balance. Body weight decreased in only the trauma patients. When these solutions were the sole source of nutrients all patients were in negative nitrogen balance and had significant decreases in their serum albumin levels. Serum albumin levels were preserved only when extra sources of calories were provided. The infusion of the crystalline amino acids without adequate levels of nonprotein energy did not conserve protein in these stressed patients.

Why Critically Ill Patients Are Protein Deprived

“…Thereafter, further increases in energy provision lead to only slight further improvements in nitrogen balance, 94 especially in critical illness, 4 , 92 , 95 and with increasing toxicity. A minimum amount of energy may be important in critical illness, 96 but it is unlikely to exceed 50% of energy expenditure (it might be considerably less than this) as long as protein provision is increased enough to compensate for the impairment of protein retention created by the hypocaloric state 79 . Experts who are aware of this evidence recommend limiting calorie provision to ~15 kcal/kg normal dry body weight per day in patients whose fat reserve is adequate 97 ; one of us has recommended that calorie provision not exceed around two‐thirds of energy expenditure when the fat reserve is adequate, with the proviso that protein provision must be suitably generous 1 , 82 .…”

Blunt Thoracoabdominal Injury

“…High-calorie regimens may result in hyperglycemia and serum hyperosmolality in the presence of glucose intolerance which commonly occurs in these patients. 20 High-calorie intake does not prevent persisting visceral protein loss because, in the presence of high levels of circulating insulin, the amino acids and glucose administered are preferentially directed to skeletal muscle protein synthesis. 21,22 Investigations are currently being directed toward the identification of metabolically active nutritional regimens, in particular those utilizing intravenously administered mixtures of branched chain amino acids and glucose with a lower caloric content than previously thought desirable.…”