[Amino acid and protein metabolism in critically ill patients]

This study set out to investigate the alteration of amino acid (AA) and protein metabolism in patients with malnutrition, sepsis, acute pancreatitis and liver diseases. The results showed that in preoperative patients with malnutrition or protein catabolism (decreased levels of plasma proteins, increased urea production rate) the postoperative complications were significantly increased. An increased postoperative infusion of branched chain AA did not improve postoperative nitrogen retention nor plasma protein syntheses in patients with colon or rectum CA. Patients with sepsis or acute pancreatitis had drastically reduced levels of total muscular free AA, mainly due to a fall in muscle glutamine. In septic patients also the hepatic levels of free AA were decreased. These changes of AA metabolism found in clinical situation were not always reflected by results found in experimental rat models (sepsis, pancreatitis, burn injury). The parenteral administration of a synthetic dipeptide containing glutamine and alanine decreased the muscular decrease of glutamine and alanine and increased the hepatic uptake of these two AA in a catabolic dog model. In critically ill patients changes in amino acid and protein metabolism lead to a protein catabolic situation. Urea production rate and muscle glutamine levels seem to be closely related to the prognosis of catabolic patients.