Is it possible to evaluate the efficacy of amino acid solutions after major surgical procedures or accidental injuries? Evaluation in a randomized and prospective study

Appearance of individual amino acid concentrations in arterial blood during steady-state infusions of different amino acid formulations to ICU patients in support of whole-body protein metabolism

BACKGROUND

Previous work has demonstrated a relationship between arterial amino acid concentrations and uptake of amino acids across peripheral tissues in healthy volunteers, as well as in chronically and acutely ill patients. The aim of the present study was to evaluate whether different amino acid profiles in commercially available amino acid formulations are translated into significantly different arterial amino acid concentrations presumably high enough to promote protein metabolism in intensive care unit (ICU) patients.

METHODS

Nonprotein calories (60% glucose: 40% lipid) were simultaneously and constantly infused over 72 hours. Different free amino acid solutions were infused at random to each patient for 24 hours in order to determine the appearance of steady-state arterial concentrations of individual amino acids. Basal metabolic and nutrition states were defined after a 12-hour infusion period with glucose in each patient. Healthy volunteers receiving a standardized oral meal served as reference subjects in measurements of venous amino acid concentrations after normal oral food intake.

RESULTS

The sum of all amino acids in arterial plasma increased significantly during steady-state infusions of all the free amino acid solutions vs basal state in ICU patients. Only glutamine, taurine, and tyrosine did not increase at all vs basal state during steady-state infusions of the 3 formulations. Alanine, arginine, citrulline, glycine, histidine, serine, methionine, phenylalanine, valine, and ornithine showed different concentration among the amino acid solutions during infusions. Healthy volunteers had significantly higher overall concentrations of amino acids in both fasted and fed state compared with ICU patients, which indicates that free amino acid solutions remain a limiting component in artificial nutrition to patients to promote arterial amino acid concentrations in the artificially fed state.

CONCLUSIONS

It appears important to continue further improvement of composition profile in solutions of free amino acids to promote adequate uptake across organ beds in promotion of protein balance in artificially nourished patients.

Therapeutic use of branched-chain amino acids in burn, trauma, and sepsis

Various experimental studies conducted in the 1970s demonstrated, at least in the physiological situation, the anabolic and/or anticatabolic properties of branched-chain amino acids (leucine, valine, isoleucine) or their ketoacid derivatives. This led to several clinical studies in the late 1970s and early 1980s that aimed to evaluate the potential benefits of BCAA supplementation in nutritional support of the critically ill. The data on burn, trauma, and sepsis are, however, far from convincing. Besides significant discrepancies in their results and the fact that most of these studies involved very small populations of patients, few of them meet the current standards of therapeutic evaluation. However, some positive results in specific studies suggest that the underlying concept may be correct but that interpretation has been faulty. Indeed, we know now that while the BCAAs possess regulatory properties on protein metabolism, leucine is by far the most potent, while isoleucine and valine are inefficient. However, in the above-mentioned studies, BCAA-supplemented nutrition very frequently supplied almost equivalent amounts of all 3 BCAAs. Moreover, several studies were performed without adequate basal nutritional support, which most probably hampered the correct metabolic utilization of these amino acids. Taken together, these factors mean that the demonstrations of BCAA efficacy were fortunate in the least. In contrast, more recently, leucine was demonstrated to positively affect protein synthesis in an experimental model of sepsis or burn. In parallel, 2 prospective controlled trials of BCAA supplementation in septic patients also demonstrated an improvement in patients' nutritional status and outcome. Thus, we should abandon the concept of BCAA-supplemented nutrition for a more promising leucine-supplemented nutrition that requires further evaluation.

Parenteral administration of different amounts of branch-chain amino acids in septic patients: clinical and metabolic aspects

OBJECTIVE

To study the effects of a total parenteral nutrition solution changing branch-chain amino acid concentrations and/or nitrogen supply on protein metabolism, length of stay, and mortality rate; and to evaluate the unique metabolic status of sepsis that leads to a search for specific total parenteral nutrition formulas.

DESIGN

Prospective, randomized, and multicenter study.

SETTING

Intensive care units (ICUs) in seven university hospitals.

PATIENTS

Sixty-nine septic patients.

MEASUREMENTS AND MAIN RESULTS

The patients were randomized into three groups according to the total parenteral nutrition administered. Group A (n = 22) and B (n = 25) patients received 1.5 g of amino acids/kg/day with a nonprotein ratio of 100:1 calories/g of nitrogen, and a varying branch-chain amino acids percentage (group A [23%); group B [45%]). Group C patients were treated with 1.1 g/kg/day of amino acids with a nonprotein ratio of 140:1 calories/g of nitrogen and 45% branch-chain amino acids. All diets were isocaloric. Prealbumin, retinol-binding protein, nitrogen balance, and plasma amino acid profiles (24 amino acids) were determined at baseline and after 3, 7, and 11 days of total parenteral nutrition. The length of stay and the mortality rate in the ICU were recorded. At baseline (preparenteral nutrition), no differences in age, gender, severity of the condition, or clinical chemistry were found between the groups. Prealbumin and retinol-binding protein increased in groups B (p < .004, p < .002, respectively) and C (p < .001, p < .002, respectively). Plasma arginine increased significantly in group C (p < .05), and plasma valine (p < .0001, p < .04, respectively), leucine (p < .005, p < .03, respectively), and isoleucine (p < .001, p < .0001, respectively) increased significantly in groups B and C. The length of stay in the ICU did not change between the groups. The mortality rate in groups B and C was less than in group A (p < .03).

CONCLUSIONS

Our results suggest that the branch-chain amino acids-rich formulas (45%) show a beneficial effect in septic patients.

The effect on energy and nitrogen metabolism by continuous, bolus, or sequential infusion of a defined total parenteral nutrition formulation in patients after major surgical procedures

BACKGROUND

The role of IV infusion kinetics to explain nutrition efficiency was investigated in patients after major surgical procedures.

METHODS

IV nutrition was provided as three different infusion kinetic regimens in a randomized fashion. All patients received nonprotein calories (100% of predicted preoperative REE, 60% D-glucose, 40% fat) and amino acid nitrogen (0.2 g N/d). Group A: Nutrition was provided by sequential infusion with combined fat and amino acids during daytime and glucose alone during nighttime ("sequential infusion"). Group B: Patients received 24-hour combined infusion with fat, amino acids, and glucose (all in one mixture) ("continuous infusion"). Group C: Nutrition was provided by bolus infusions during 1 hour followed by 2 hours without any infusion ("bolus infusion").

RESULTS

The daily energy balance was negative in all groups (-318 +/- 25 kcal/d, sequential infusion; -368 +/- 25 kcal/d continuous infusion; -292 +/- 20 kcal/d, bolus infusion). Significantly different excretion patterns of nitrogen in urine occurred among the groups despite an almost identical provision of nitrogen. Continuously infused patients retained nitrogen significantly better (-0.2 +/- 0.6 g/d) compared with sequentially (-3.4 +/- 1.0 g/d) and bolus-infused patients (-2.8 +/- 0.3 g/d) (p < .01), whereas their cumulative urinary glucose excretion was significantly larger. Continuously infused patients were in cumulative nitrogen balance during the entire postoperative period, whereas the other groups were in a significantly negative nitrogen balance. Urinary 3-methylhistidine excretion was similar in all groups.

CONCLUSIONS

The breakdown of muscle proteins was not sensitive to alterations in nutrient and substrate supply. Thus improved nitrogen retention reflected entirely improved synthesis. "All-in-one" IV nutrition with prolonged infusion periods is at present the most favorable regimen considering both the nutritional efficiency and its metabolic load on the organism after major surgery.

The effects of a new amino-acid dipeptide solution on nitrogen balance and humoral growth factors in the postoperative state in man

27 patients admitted for elective abdominal surgery were allocated to receive postoperative total parenteral nutrition supplemented with glutamine (glycyl-glutamine) and tyrosine (glycyl-tyrosine) containing dipeptides (DP-Gln 20; 0.16 g glutamine/kg BW/24 h) or isonitrogenous Vamin 18 for 5 days. The aim was to evaluate safety and effects on short-life plasma proteins, nitrogen balance, 3-methylhistidine excretion and alimentary growth factors in plasma. No differences in transthyretin or retinol binding protein levels, nitrogen balance or 3-methylhistidine excretion were found in patients receiving DP-Gln 20 compared to Vamin 18. There were higher plasma levels of peptide YY in the dipeptide group 5 days after surgery (p < 0.05). A correlation between insulin levels and nitrogen balance was found only in DP-Gln 20 treated patients day 6 (r = 0.91, p < 0.01). DP-Gln 20 is a glutamine dipeptide (Gly-Gln) containing amino acid solution which is considered safe in the postoperative state in man. No beneficial effects on whole body protein metabolism were found by adding DP-Gln 20 to total parenteral nutrition.

The effect of postoperative intravenous feeding (TPN) on outcome following major surgery evaluated in a randomized study

Three hundred patients undergoing major general surgical procedures were randomized by means of a computer-assisted algorithm to receive either total parenteral nutrition (TPN) from the first postoperative day or only prolonged glucose administration (250-300 g/day) up to 15 days after operation. All patients receiving TPN were treated individually based on daily measurements of energy and nitrogen balances. The treatment goal was to keep the patients in positive energy balance (+20%) and close to nitrogen balance. The effects of the two "nutrition regimens" on outcome such as mortality rate, complications, the need of additional medical support and patient-related functional disabilities were investigated. No selection of patients was made, that is, malnourished patients were also randomized. There were no differences among TPN versus glucose treatment when results were analyzed according to intent to treat. Approximately 60% of all patients were able to start eating within 8 to 9 days after operation. No differences were observed between such patients regardless of being treated with TPN or glucose only. Patients on glucose treatment during 14 days had a significantly higher mortality rate (p < 0.05) than patients on either continuous and uncomplicated TPN treatment or short-term glucose treatment. Similar results for mortality rates also were seen with regard to severe complications (cardiopulmonary problems, sepsis, and wound-healing insufficiencies), functional disturbances, the need of additional medical support, and abnormalities in nutritional state. Twenty per cent of the patients randomized to TPN treatment showed a statistical trend (p < 0.10) toward a higher mortality rate (36%) compared with patients randomized to prolonged glucose treatment (21% mortality rate). These patients could not be identified by evaluation of preoperative factors. Thus, the overall evaluation of the results makes it likely that a fraction of high-risk patients (approximately 20%) were not doing well on immediate postoperative intravenous feeding, and it is possible that TPN to such patients accentuated their morbidity rate. Although patients (20%) on prolonged semi-starvation (14 days glucose treatment) had increased mortality rate and severe complications, it was possible that undernutrition induced a slightly different complication scenario than induced by TPN in the high-risk patients. The results demonstrate that in most surgical patients (60%), postoperative semi-starvation is not a limiting factor for outcome. In remaining 40%, inadequate nutrition was associated with both increased morbidity and mortality rates. In this sense, inadequate nutrition represents both too much and too little, whereas overfeeding seemed to be a larger problem than underfeeding.(ABSTRACT TRUNCATED AT 400 WORDS)

Nutritional support in the injured patient

After injury, the stress reaction causes hypermetabolism and consequent depletion of the body's tissues. Nutritional support should be begun early and should be given by the enteral route if possible. New developments may allow the modulation of the stress and immune responses by nutrient therapy.

Effect of branched chain amino acid enrichment of total parenteral nutrition on nitrogen sparing and clinical outcome of sepsis and trauma: a prospective randomized double blind trial

Administration of extra branched chain amino acids (BCAA) has been associated with a nitrogen sparing effect in septic and traumatized patients. Whether nitrogen sparing is associated with decreased morbidity and mortality rates is unknown. We therefore undertook a prospective, randomized, double blind trial investigating the effects of BCAA enrichment of a total parenteral nutrition (TPN) regimen on nitrogen balance, 3-methylhistidine excretion, morbidity as evidenced by disturbances in organ function, severity of sepsis and mortality. One hundred and one patients entered the study; 52 received a standard TPN solution and 49 a BCAA-enriched solution. Both groups received 30 kcal kg-1 body-weight, 15 per cent fat calories and 0.17 g nitrogen kg-1 body-weight. In the BCAA-enriched group, patients received 0.56 g BCAA kg-1 body-weight (50.2 per cent BCAA). Standard group patients received 0.18 g BCAA kg-1 body-weight (15.6 per cent BCAA). Nitrogen balances and 3-methylhistidine excretion were not significantly different between groups. Although morbidity scores tended to decrease during the study no difference was observed between groups. Mortality (early or late), sepsis or stress-related, did not differ significantly between groups. We were not able to confirm the reported beneficial effects of BCAA-enriched TPN solutions for use in septic and traumatized patients.

A key to the literature of total parenteral nutrition: update 1987

This comprehensive bibliography is intended to enhance the education of the practitioner, student, and academician in the area of parenteral nutrition. This bibliography is not all-inclusive but serves as an update from the original published in 1983. Of particular note in this work is the addition of topics that reflect a growing interest in medical specialties with regard to patient nutritional status and support.