Changes of serum amino acids in severely burned patients

Nutritional therapy in critically ill and injured patients

Nutritional support of critically ill or injured patients has undergone significant advances in the last few decades. These advances are the direct result of the growing scientific progress and increased knowledge of the biology and biochemistry of key metabolic and nutrient changes induced by injury, sepsis, and other critical illnesses, both in adults and children. As this knowledge has increased, the science of nutritional support has become more disease based and disorder based. This article discusses protein and nitrogen metabolism in critically ill patients, immunomodulation, and the key nutrients involved in an immune-enhancing diet.

Early plasma amino acid pool alterations in patients with military gunshot/missile wounds

Plasma amino acid profiles in patients during the early period (first 18 hours) following military gunshot/missile wounds were investigated. Patients (n = 29) were casualties from the war in the former Yugoslavia with injury severity scores ranging from 4 to 18. They were divided into three groups: soft tissue (muscle) damage, wounds with fractures, and vital structures injured. Controls were normal blood donors (n = 17). Free amino acids were analyzed in venous plasma. Increased concentrations of phenylalanine and glutamine associated with increased molar phenylalanine/tyrosine ratio in plasma indicated increased net protein catabolism in the peripheral tissues, regardless of the type of injured tissues. Decreased plasma arginine, ornithine and citrulline levels, accompanied with increased molar glutamine/valine ratio, suggested disturbance in urea cycle activity, although urea level was not altered. We concluded that early changes in plasma amino acid pool characteristics after wounds were of systemic origin, not related to the type of injured tissues.

Does glutamine contribute to immunosuppression after major burns?

The effects of glutamine concentration on the rates of lymphocyte proliferation after mitogenic stimulation and of phagocytosis by macrophages were investigated in vitro. A decrease in the glutamine concentration in culture medium from 0.6 to 0.05 mmol/l greatly decreased the rate of proliferation of human lymphocytes and of phagocytosis by mouse macrophages. In patients with major burn injury plasma glutamine concentration was 58% lower than that in normal controls and it remained low for at least 21 days after the injury. The findings indicate that the decrease in plasma glutamine concentration may contribute to the injury-induced impairment of immune function occurring after major burn injury.

Phenylalanine: total amino acid ratio in 45 burn patients

In 45 burn patients serum amino acids together with liver enzymes and other serum parameters were determined. Phe levels, Phe:Tyr and Phe:TAA ratios were correlated with the clinical course of the patient's condition. Based on empirical data, an increase in the Phe:TAA ratio of over 3% was found to be the best indicator of a critical period in the clinical course. An increase in the Phe:TAA ratio above 3% accompanied the signs of sepsis. If the patient recovered, the ratio decreased. Ratios which kept constant or even increased--indicating a possible fatal clinical outcome--were found to be alarming. In our experience Phe levels or Phe:Tyr ratios did not have indicative functions.

Effects of nutrition on plasma, liver and muscle amino acids in scalded rats

This study set out to investigate the effect of three different parenterally administered diets on the free amino acid (AA) levels in the plasma, muscle, and liver of scalded rats. Diet I consisted of AA (1.4 g/100 g weight) and a high glucose dose (6 g/100 g weight), diet II consisted of AA and a low glucose dose (1.4 g/100 g weight) and in diet III only a low glucose dose was infused. Parenteral nutrition was started on the 3rd day posttraumatically. Sampling was performed on the 7th day posttraumatically. Nitrogen balances were significantly different in all three groups, being lowest in group III. Scalded rats fed isonitrogenously, but with different amounts of glucose showed only minor changes in AA concentrations. However scalded rats fed with a nitrogen-free diet exhibited significantly reduced total muscle and liver AA levels. These decreased AA levels were due to a drop of glycine in the muscle tissue (74%) and liver (49%). Contrary to the clinical catabolic situation in scalded and starved rats, it was not intracellular glutamine but glycine which was considerably influenced by catabolism and starvation.

Effects of burns on amino acid levels in rat plasma, liver and muscle

In this study the influence of a severe catabolic situation (scalding and nitrogen deprivation) on amino acid (AA) metabolism was investigated in an experimental rat model. Scalding of 25 per cent of the total body surface area (TBSA) and hypocaloric alimentation (5.6 kcal per 100 g rat per day, no nitrogen) resulted in mean daily nitrogen losses of -0.27 +/- 0.3 g. Compared to anabolic growing rats this nitrogen catabolism significantly reduced the total free AA content of muscle (-47 per cent, P less than 0.001) and liver (-39 per cent, P less than 0.001). The total plasma AA concentrations were slightly increased in catabolic rats (+10 per cent). In catabolic rats muscle glycine concentrations dropped significantly (-79 per cent, P less than 0.001), while glutamine concentrations decreased by 22 per cent, which was not significant. Branched chain AA and phenylalanine were significantly elevated both in muscle and in plasma. Scalding and nitrogen depletion in rats leads to characteristic changes in plasma, muscle and liver AA concentrations, which are comparable to the results obtained in catabolic patients. However, the low muscle glycine concentrations in burned rats differ from the clinical observations where glutamine rather than glycine concentrations in muscle tissue are reduced. The rat model seems to be well suited for studying the influence of various therapeutic approaches such as different forms of parenteral nutrition or hormonal substitution on nitrogen catabolism.