[Nutrition proteins and muscular catabolism in severely burnt patients. Comparative effects of small peptides or free amino acids]

Immunonutrition as an adjuvant therapy for burns

BACKGROUND

With burn injuries involving a large total body surface area (TBSA), the body can enter a state of breakdown, resulting in a condition similar to that seen with severe lack of proper nutrition. In addition, destruction of the effective skin barrier leads to loss of normal body temperature regulation and increased risk of infection and fluid loss. Nutritional support is common in the management of severe burn injury, and the approach of altering immune system activity with specific nutrients is termed immunonutrition. Three potential targets have been identified for immunonutrition: mucosal barrier function, cellular defence and local or systemic inflammation. The nutrients most often used for immunonutrition are glutamine, arginine, branched-chain amino acids (BCAAs), omega-3 (n-3) fatty acids and nucleotides.

OBJECTIVES

To assess the effects of a diet with added immunonutrients (glutamine, arginine, BCAAs, n-3 fatty acids (fish oil), combined immunonutrients or precursors to known immunonutrients) versus an isonitrogenous diet (a diet wherein the overall protein content is held constant, but individual constituents may be changed) on clinical outcomes in patients with severe burn injury.

SEARCH METHODS

The search was run on 12 August 2012. We searched the Cochrane Injuries Group's Specialised Register, The Cochrane Library, MEDLINE (OvidSP), Embase (OvidSP), ISI WOS SCI-EXPANDED & CPCI-S and four other databases. We handsearched relevant journals and conference proceedings, screened reference lists and contacted pharmaceutical companies. We updated this search in October 2014, but the results of this updated search have not yet been incorporated.

SELECTION CRITERIA

Randomised controlled trials comparing the addition of immunonutrients to a standard nutritional regimen versus an isonitrogenated diet or another immunonutrient agent.

DATA COLLECTION AND ANALYSIS

Two review authors were responsible for handsearching, reviewing electronic search results and identifying potentially eligible studies. Three review authors retrieved and reviewed independently full reports of these studies for inclusion. They resolved differences by discussion. Two review authors independently extracted and entered data from the included studies. A third review author checked these data. Two review authors independently assessed the risk of bias of each included study and resolved disagreements through discussion or consultation with the third and fourth review authors. Outcome measures of interest were mortality, hospital length of stay, rate of burn wound infection and rate of non-wound infection (bacteraemia, pneumonia and urinary tract infection).

MAIN RESULTS

We identified 16 trials involving 678 people that met the inclusion criteria. A total of 16 trials contributed data to the analysis. Of note, most studies failed to report on randomisation methods and intention-to-treat principles; therefore study results should be interpreted with caution. Glutamine was the most common immunonutrient and was given in seven of the 16 included studies. Use of glutamine compared with an isonitrogenous control led to a reduction in length of hospital stay (mean stay -5.65 days, 95% confidence interval (CI) -8.09 to -3.22) and reduced mortality (pooled risk ratio (RR) 0.25, 95% CI 0.08 to 0.78). However, because of the small sample size, it is likely that these results reflect a false-positive effect. No study findings suggest that glutamine has an effect on burn wound infection or on non-wound infection. All other agents investigated showed no evidence of an effect on mortality, length of stay or burn wound infection or non-wound infection rates.

AUTHORS' CONCLUSIONS

Although we found evidence of an effect of glutamine on mortality reduction, this finding should be taken with care. The number of study participants analysed in this systematic review was not sufficient to permit conclusions that recommend or refute the use of glutamine. Glutamine may be effective in reducing mortality, but larger studies are needed to determine the overall effects of glutamine and other immunonutrition agents.

Plasma glucagon and insulin responses depend on the rate of appearance of amino acids after ingestion of different protein solutions in humans

To find out whether the hormonal response to feeding with protein solutions is influenced by the nature and degree of protein fractionation, we examined insulin and glucagon responses after intake of protein solutions containing the same amount of nitrogen (2.9 g each) in three men and three women. Four test meals (600 mL) [glucose (419 kJ/L), pea (PPH) and whey peptide hydrolysates (WPH) (921 and 963 kJ/L, respectively) and a cow's milk solution (MS) containing complete milk proteins (2763 kJ/L)] were tested. Peptide hydrolysates elicited a faster increase in venous plasma amino acids than did MS (P < 0.05). Despite the higher carbohydrate content of the MS, the peptide hydrolysates elicited a peak insulin response that was two and four times greater than that evoked by the MS and glucose solutions, respectively (P < 0.05). The insulin response was closely related to the increase in plasma amino acids, especially leucine, isoleucine, valine, phenylalanine and arginine, regardless of the rate of gastric emptying. The three protein solutions elicited similar increases of plasma glucagon; however, the response was fastest for both peptide hydrolysates (P < 0.05) and more prolonged for the MS (P < 0.05). The glucagon response was linearly related to the increase in plasma amino acids, regardless of the rate of gastric emptying or meal composition (r = 0.93, r = 0.96 and r = 0.78, all P < 0.05, for the PPH, WPH and MS). Among the plasma amino acids, tyrosine (r = 0.82-0.98, P < 0.05) and methionine (r = 0.98, P < 0.001) were most closely related to the plasma glucagon response. This study shows that the glucagon response to feeding with protein solutions depends on the increase in plasma amino acid concentrations. The combined administration of glucose and peptide hydrolysates stimulates a synergistic release of insulin, regardless of the protein source.

[Role of albumins in burnt patients: its efficacy during intensive care. Addendum to the expert guidelines of the Consensus Conference, Paris December 15th 1995]

In the burned patient, the critical threshold over which a correction of hypoalbuminemia is required has not yet been clearly defined. The level of 30 g.L-1 of albumin is usually admitted. According to the extent of the burn, albumin is not indicated in patients with a burn size below 15% of the total body surface. It is essential, from the very beginning of management in patients with a burn size over 50%. Its administration can be postponed to the 8th, 12th or even 24th hour in case of a burn size between 15 and 50%.