Specific amino acids in the critically ill patient--exogenous glutamine/arginine: a common denominator?

Immunonutrition in critically ill patients: a systematic review and analysis of the literature

BACKGROUND

The role of immuno-modulating diets (IMDs) in critically ill patients is controversial.

OBJECTIVE

The goal of this meta-analysis was to determine the impact of IMD's on hospital mortality, nosocomial infections and length of stay (LOS) in critically ill patients. Outcome was stratified according to type of IMD and patient setting.

DATA SOURCES

MEDLINE, Embase, Cochrane Register of Controlled Trials.

STUDY SELECTION

RCT's that compared the outcome of critically ill patients randomized to an IMD or a control diet.

DATA SYNTHESIS

Twenty-four studies (with a total of 3013 patients) were included in the meta-analysis; 12 studies included ICU patients, 5 burn patients and 7 trauma patients. Four of the studies used formulas supplemented with arginine, two with arginine and glutamine, nine with arginine and fish oil (FO), two with arginine, glutamine and FO, six with glutamine alone and three studies used a formula supplemented with FO alone. Overall IMD's had no effect on mortality or LOS, but reduced the number of infections (OR 0.63; 95% CI 0.47-0.86, P = 0.004, I(2) = 49%). Mortality, infections and LOS were significantly lower only in the ICU patients receiving the FO IMD (OR 0.42, 95% CI 0.26-0.68; OR 0.45, 95% CI 0.25-0.79 and WMD -6.28 days, 95% CI -9.92 to -2.64, respectively).

CONCLUSIONS

An IMD supplemented with FO improved the outcome of medical ICU patients (with SIRS/sepsis/ARDS). IMDs supplemented with arginine with/without additional glutamine or FO do not appear to offer an advantage over standard enteral formulas in ICU, trauma and burn patients.

Immunonutrition in critically ill patients: a systematic review and analysis of the literature

BACKGROUND

The role of immuno-modulating diets (IMDs) in critically ill patients is controversial.

OBJECTIVE

The goal of this meta-analysis was to determine the impact of IMD's on hospital mortality, nosocomial infections and length of stay (LOS) in critically ill patients. Outcome was stratified according to type of IMD and patient setting.

DATA SOURCES

MEDLINE, Embase, Cochrane Register of Controlled Trials.

STUDY SELECTION

RCT's that compared the outcome of critically ill patients randomized to an IMD or a control diet.

DATA SYNTHESIS

Twenty-four studies (with a total of 3013 patients) were included in the meta-analysis; 12 studies included ICU patients, 5 burn patients and 7 trauma patients. Four of the studies used formulas supplemented with arginine, two with arginine and glutamine, nine with arginine and fish oil (FO), two with arginine, glutamine and FO, six with glutamine alone and three studies used a formula supplemented with FO alone. Overall IMD's had no effect on mortality or LOS, but reduced the number of infections (OR 0.63; 95% CI 0.47-0.86, P = 0.004, I(2) = 49%). Mortality, infections and LOS were significantly lower only in the ICU patients receiving the FO IMD (OR 0.42, 95% CI 0.26-0.68; OR 0.45, 95% CI 0.25-0.79 and WMD -6.28 days, 95% CI -9.92 to -2.64, respectively).

CONCLUSIONS

An IMD supplemented with FO improved the outcome of medical ICU patients (with SIRS/sepsis/ARDS). IMDs supplemented with arginine with/without additional glutamine or FO do not appear to offer an advantage over standard enteral formulas in ICU, trauma and burn patients.

Glutamine is an important precursor for de novo synthesis of arginine in humans

BACKGROUND

A metabolic relation exists between glutamine and arginine, 2 amino acids with properties that enhance the recovery of seriously ill patients. It is possible that glutamine exerts part of its beneficial effects by enhancing the availability of arginine.

OBJECTIVES

We aimed to quantify under postabsorptive conditions the metabolic pathway of plasma glutamine into arginine via the intermediate citrulline and to establish the contribution of the kidneys to the synthesis of arginine.

DESIGN

The study was conducted in patients during surgery. The metabolism of glutamine, citrulline, and arginine was studied by using intravenous administration of stable isotope tracers of the amino acids. Results were interpreted by using established equations. Parametric tests were used to test and correlate results. P < 0.05 was regarded as significant.

RESULTS

Mean (+/-SE) whole-body plasma turnover rates of glutamine, citrulline, and arginine were 240 +/- 14, 6.2 +/- 0.6, and 42 +/- 2.9 micromol x kg(-1) x h(-1), respectively (P < 0.01). Plasma turnover of citrulline derived from glutamine was shown to be 5.1 +/- 0.7 micromol x kg(-1) x h(-1), and arginine derived from citrulline was shown to be 4.9 +/- 0.9 micromol x kg(-1) x h(-1) (P < 0.01). The contribution of plasma glutamine to plasma arginine derived from plasma citrulline was calculated to be 64%. The kidneys were observed to take up >50% of circulating plasma citrulline and to release equimolar amounts of arginine into plasma.

CONCLUSIONS

This study shows that glutamine is an important precursor for the synthesis of arginine in humans. It also provides a firm basis for future studies exploring the effect of a treatment dose and the route of administration (enteral or parenteral) of glutamine.