Nutritional support in critically ill patients

Evolution of the Maillard Reaction in Glutamine or Arginine-Dextrinomaltose Model Systems

Enteral formulas are foods designed for medical uses to feed patients who are unable to eat normally. They are prepared by mixing proteins, amino acids, carbohydrates and fats and submitted to sterilization. During thermal treatment, the Maillard reaction takes place through the reaction of animo acids with reducing sugars. Thus, although glutamine and arginine are usually added to improve the nutritional value of enteral formulas, their final concentration may vary. Thus, in the present paper the early, intermediate, and advanced states of the Maillard reaction were studied in model systems by measuring loss of free amino acids through the decrease of fluorescence intensity with o-phtaldialdehyde (OPA), 5-Hydroximethylfurfural (HMF), furfural, glucosylisomaltol, fluorescence, and absorbance at 420 nm. The systems were prepared by mixing glutamine or arginine with dextrinomaltose (similar ingredients to those used in special enteral formula), and heated at 100 °C, 120 °C and 140 °C for 0 to 30 min. The recorded changes in the concentration of furanic compounds was only useful for longer heating times of high temperatures, while absorbance and fluorescence measurements were useful in all the assayed conditions. In addition, easiness and sensitivity of absorbance and fluorescence make them useful techniques that could be implemented as indicators for monitoring the manufacture of special enteral formulas. Glucosylisomaltol is a useful indicator to monitor the manufacture of glutamine-enriched enteral formulas.

Advanced enteral therapy in acute pancreatitis: is there a room for immunonutrition? A meta-analysis

BACKGROUND

It is believed that certain nutrients such as glutamine, arginine and omega-3 fatty acids may play a significant role in metabolic, inflammatory, and immune processes in acute pancreatitis. The present systematic review aimed to define whether the addition of these substances to enteral nutrition provides any clinical benefit over standard enteral formulas in patients with acute pancreatitis.

METHODS

A computerized search on electronic databases (Cochrane Central Register of Controlled Trials, EMBASE and MEDLINE) and manual search of the abstracts of major gastroenterological meetings (UEGW, DDW) were undertaken. The studied outcomes were total infectious complication, in-hospital mortality and length of hospital stay. The data were meta-analyzed using a random-effects model.

RESULTS

A total of three randomized controlled trials satisfied the inclusion criteria. When compared with standard enteral nutrition, immunonutrition was not associated with the significantly reduced risk of total infectious complications (risk ratio 0.82; 95% confidence interval 0.44-1.53; P=0.53) and death (risk ratio 0.64; 95% confidence interval 0.20-2.07; P=0.46). Mean difference in length of hospital stay between two groups was not significant (P=0.80).

CONCLUSIONS

There is no evidence that enteral nutrition supplemented with glutamine, arginine and/or omega-3 fatty acids, in comparison with standard enteral nutrition, has any beneficial effect on infectious complications, mortality or length of hospital stay in acute pancreatitis. The pursuit of new compositions of enteral formulations in this category of patients may be advocated.

Effect of timing of glutamine-enriched enteral nutrition on intestinal damage caused by irradiation

Intestinal mucosal damage and bacterial translocation are clinical problems that may be caused by the use of ionizing radiation. Glutamine (Gln) support reduces the mucosal barrier in several ways. This study was undertaken to investigate the effect of timing of Gln-enriched enteral nutrition (EN) on bacterial translocation and mucosal damage due to radiotherapy (RT). A rat model of whole body irradiation was designed in which a single dose of 485 cGy was given. A total of 50 rats were randomly assigned to the following 5 groups, each of which comprised 10 rats: (1) balanced rat chow given for 8 days without RT (group 1); (2) balanced rat chow given 4 days before and 4 days after RT (group 2); (3) Gln-enriched EN given 4 days before RT (group 3); (4) Gln;enriched EN given 4 days after RT (group 4); and (5) Gln-enriched EN given 4 days before and 4 days after RT (group 5). Mesenteric lymph node and ileum samples were removed for evaluation of bacterial translocation (BT) and histopathologic investigation, respectively. BT and intestinal mucosal injury scores in all rats that received RT were higher than in rats without RT. No difference was seen in parameters between groups 3 and 4 (P>.05, P>.016, respectively); BT and intestinal mucosal injury scores of group 5 were significantly lower than those of groups 3 and 4 (P<.05, P<.016, respectively). Meanwhile, the BT and mesenteric injury scores of group 5 were significantly lower than those of group 2 (P<.05, P<.016, respectively). As a result, intestinal injury due to RT was significantly decreased by Gln-enriched EN support given before and after whole body RT.

Fluid resuscitation and nutritional support during severe acute pancreatitis in the past: what have we learned and how can we do better?

BACKGROUND/AIMS

Severe acute pancreatitis is associated with microcirculatory impairment, increased gut permeability and metabolic changes. The aim of the present study was to evaluate initial fluid resuscitation and nutritional support versus outcome in patients with severe acute pancreatitis.

METHODS

All cases of acute pancreatitis admitted 1994-2003 were analyzed retrospectively. The inclusion criteria of severe acute pancreatitis were organ failure and/or local complications according to the Atlanta classification system. Mortality was used as outcome measure.

RESULTS

Ninty-nine patients were included in the study. The hospital mortality was 17%. Hypovolemia at arrival was found in 13% (13/99) and correlated with increased hospital mortality (P=0.009). During the first three days in average 11000+/-4100 ml of fluids and 1470+/-820 calories were administered. Total parental nutrition was given to 73% (69/95) and enteral nutrition served as a complement in 29% (28/95) of the patients. Hyperglycemia was seen in 61% (55/90) of the patients and insulin was administered to 53% (29/55) at an average glucose level of 19+/-3 mmol/l. The intake of oral food was reintroduced in average 15+/-9 days after admission and was interrupted in 17% (13/75) because of pain relapse.

CONCLUSION

A nutritional treatment regime in severe acute pancreatitis including a moderate and hypocaloric initial fluid resuscitation, parental nutrition as the preferred route for nutritional support and a non-strict glucose control, with an associated mortality of 17%, indicates several modes of improving outcome.

Metabolic and hematological effects of dietary supplementation with arginine on rats bearing ascitic Walker 256 tumor

The notion of using supplementary quantities of arginine for nutritional support in patients with cancer has been evaluated not only as supplement intake of nitrogen substrate but also for its immunopharmacological effects capable of improving the patient's prognosis. The aim of the present study is to evaluate the effects of dietary supplementation with arginine on metastatic dissemination, amino acid metabolism, hematological functions of rats with Walker 256 ascitic tumor. Animals were inoculated intraperitoneally with approximately 4 million cells. Nutritional solutions containing 4 or 6% arginine or just a control diet without added arginine, were administered to the animals via esophagic gavages. The rate of metastasis was lower in animals supplemented with arginine at 4 and 6%. Amino acid metabolism was stimulated in tumor-bearing animals after receiving 4 or 6% arginine, demonstrated by significant increase of arginine, ornithine, citrulline, proline and histidine levels in the blood (p < or = 0.001) when compared to the control diet group. Anemia was less severe in tumor-bearing animals that received arginine supplementation. The findings suggest that arginine supplementation at 6% may have a beneficial effect on to the host, besides its pharmacological action.

Fish oil-supplemented parenteral diets normalize splanchnic blood flow and improve killing of translocated bacteria in a low-dose endotoxin rat model

OBJECTIVE

Intestinal ischemia decreases barrier function of the gut and enhances translocation of bacteria and toxins. Several studies indicate that fish oil can modulate prostaglandin formation and thus, regional blood flow and immune function. This study was performed to determine the effects of parenteral diets with omega-3 fatty acids on microcirculation and barrier function of the gut.0

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University laboratory.

SUBJECTS

A total of 64 male Sprague-Dawley CD rats.

INTERVENTIONS AND MEASUREMENTS

For 48 hrs, eight groups of eight rats each received total parenteral nutrition with four different types of lipids. The source of fat in group L was soybean oil only and in group L-M a mixture of soybean oil and medium-chain triglycerides. In groups FO-20 and FO-40, 20% or 40%, respectively, of the soybean oil in group L-M was replaced by fish oil. The other four groups received an additional continuous infusion of endotoxin (0.1 mg/100 g body weight per day) for the last 24 hrs. Blood flow was measured with microspheres, and translocation was determined by microbiological methods and instillation of radioactive-marked bacteria into the gut.

MAIN RESULTS

In the animals without fish oil, the endotoxin application reduced the blood flow to the intestine approximately 25%. Animals with fish oil in their diets showed normal values. Translocation of gut bacteria was increased significantly in all endotoxin groups. However, less-viable bacteria could be detected in the animals with fish oil diets in their mesenteric lymph nodes and livers.

CONCLUSIONS

In this model, diets enriched with fish oil abolish the endotoxin-induced decrease of nutritive blood flow to the gut and ameliorate the bactericidal defense of the splanchnic region. The lower count of viable bacteria in the fish oil groups is more related to an improved killing of translocated bacteria than a reduction of the translocation rate.

Effects of drugs on glucose measurements with handheld glucose meters and a portable glucose analyzer

Thirty drugs used primarily in critical care and hospital settings were tested in vitro to observe interference on glucose measurements with 6 hand-held glucose meters and a portable glucose analyzer. Paired differences of glucose measurements between drug-spiked samples and unspiked control samples were calculated to determine bias. A criterion of +/- 6 mg/dL was used as the cutoff for interference. Ascorbic acid interfered with the measurements on all glucose devices evaluated. Acetaminophen, dopamine, and mannitol interfered with glucose measurements on some devices. Dose-response relationships help assessment of drug interference in clinical use. High dosages of these drugs may be given to critically ill patients or self-administered by patients without medical supervision. Package inserts for the glucose devices may not provide adequate warning information. Hence, we recommend that clinicians choose glucose devices carefully and interpret results cautiously when glucose measurements are performed during or after drug interventions.

Characterization of L-leucine transport system in brush border membranes from human and rabbit small intestine

The branched-chain amino acids (BCAAs) leucine, isoleucine, and valine are beneficial to catabolic patients by improving hepatic protein synthesis and nitrogen economy, yet their transport from the intestinal lumen is not well-defined. The leucine transport system in human and rabbit small intestine was characterized using a brush border membrane vesicle (BBMV) model. Sodium and pH dependence and transport activity along the longitudinal axis of the small bowel were determined. Transport kinetics and inhibition profiles were defined. Although previous studies in other tissues show leucine transport to be mostly a Na+-independent process, our studies show that leucine transport is a predominantly Na+-dependent process occurring mainly via a single saturable pH-independent transporter resembling system B0 in the intestine. This system B0 transporter demonstrates stereoisomeric specificity. There is also a minor Na+-independent transport component (<6% in rabbits). Leucine uptake in both rabbits and humans is significantly greater than the uptake of other clinically relevant nutrients such as glutamine. In the rabbit, ileal leucine transport is significantly greater than jejunal uptake. While the affinities of the human and rabbit transporters are similar, the rabbit transporter has greater carrier capacity (maximal transport velocity [Vmax]). These findings suggest that the transport of leucine in the gut mucosa is significantly different from the transport in other tissues.

Sequential changes in the metabolic response in severely septic patients during the first 23 days after the onset of peritonitis

OBJECTIVE

To quantify the sequential changes in metabolic response occurring in patients with severe sepsis after the onset of peritonitis.

SUMMARY BACKGROUND DATA

Understanding the changes in energy expenditure and body composition is essential for the optimal management of severely septic patients; however, they have not been quantified in the context of modern surgical care.

METHODS

Twelve patients with severe sepsis secondary to peritonitis (median APACHE II score = 21.5) had measurements of energy expenditure and body composition as soon as they were hemodynamically stable and 5, 10, and 21 days later. Sequential measurements of acute-phase proteins and cytokine responses were also made.

RESULTS

Resting energy expenditure rose to 49% above predicted and remained elevated throughout the study period. Total energy expenditure was 1.25 x resting energy expenditure. Body fat was oxidized when energy intake was insufficient to achieve energy balance. There was a positive fluid balance of 12.5 1 over the first 2 days after onset of sepsis; thereafter, body water changes closely paralleled body weight changes and were largely accounted for by changes in extracellular water. During the 21 -day study period, there was a loss of 1.21 kg (13%) of total body protein. During the first 10 days, 67% of the protein lost came from skeletal muscle, but after this time it was predominantly from viscera. Intracellular potassium levels were low but did not deteriorate further after hemodynamic stability had been reached. There was a reprioritization of hepatic protein synthesis that was obligatory and independent of changes in total body protein. The cytokine responses demonstrated the complexity, redundancy, and overlap of mediators.

CONCLUSIONS

The period of hypermetabolism in severely septic patients is similar to that previously described, but the fluid changes are larger and the protein loss is greater. Protein loss early on is predominantly from muscle, thereafter from viscera. Fat loss can be prevented and cell function preserved once hemodynamic stability is achieved.

Glutamine-enhanced bacterial killing by neutrophils from postoperative patients

Neutrophils play an important role in host defense by phagocytosing and destroying invading bacteria. A recent investigation revealed that glutamine (Gln) augmented the in vitro bactericidal activity of neutrophils from burn patients. However, it is unclear whether Gln enhances the function of neutrophils in postoperative patients. This study was designed to investigate the effect of Gln on the in vitro Escherichia coli-killing activity of neutrophils from postoperative patients. Nine randomly selected patients were included in this study. On the morning of the first postoperative day, blood was drawn and neutrophils were isolated. Eight healthy volunteers served as controls. E. coli was opsonized with pooled normal serum. Neutrophils (5 x 10(6)), together with opsonized E. coli (5 x 10(5)), were incubated for 2 h at 37 degrees C in Hanks' balanced salt solution supplemented with 0, 100, 500, or 1000 nmol/mL of Gln. The bactericidal function of neutrophils was determined by counting the number of viable bacteria. Tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 beta, IL-8, and granulocyte elastase levels in the cell culture supernatant were measured. Plasma C-reactive protein (CRP), cortisol, and amino acids were also analyzed. The plasma concentration of Gln was significantly lower in the postoperative patients than in the controls. Following culture with patient neutrophils, the number of viable E. coli decreased by 26% as the in vitro Gln concentration was increased from 500 to 1000 nmol/mL (P < 0.01). We defined the Gln 1000/Gln 500 ratio of the number of viable bacteria as the number of viable E. coli at an in vitro Gln concentration of 1000 nmol/mL divided by the number of viable E. coli at an in vitro Gln concentration of 500 nmol/mL. A positive correlation was thus demonstrated between the plasma Gln level and the Gln 1000/Gln 500 ratio of the number of viable bacteria in the patients (r = 0.69, P = 0.04). This finding indicated that as plasma Gln fell, there was an enhancement of neutrophil E. coli-killing activity by neutrophils in in vitro tests when the Gln concentration was increased from 500 to 1000 nmol/mL. Gln supplementation caused no appreciable changes in TNF-alpha, IL-1 beta, IL-8, or granulocyte elastase levels in cell culture supernatants. A negative correlation was recognized between the patient plasma Gln level and the Gln 1000/Gln 500 ratio of the cell culture supernatant IL-8 level (r = -0.73, P = 0.025). In conclusion, Gln supplementation enhanced the in vitro bactericidal function of neutrophils from postoperative patients.

Glutamine-enriched enteral diet enhances bacterial clearance in protected bacterial peritonitis, regardless of glutamine form

BACKGROUND

The effects of glutamine (Gln)-enriched enteral diets on bacterial clearance were investigated in a rat protracted peritonitis model. The effects of the Gln form, peptide-based vs free amino acid-based, were also compared.

METHODS

Twenty-three rats underwent gastrostomy. An osmotic pump was implanted in the peritoneal cavity. The rats received a continuous intragastric infusion of one of three diets: Gln-depleted (Gln 0), Gln-enriched with the Gln in free amino acid form (Gln F), or Gln-enriched with the Gln in oligopeptide form (Gln P). The three formulas were isocaloric and isonitrogenous. The pumps delivered a continuous infusion of Escherichia coli, starting at 48 hours after implantation, for 24 hours. Then, the animals were killed.

RESULTS

Bacterial numbers in peritoneal lavaged fluid (PLF) and the liver were significantly lower in the Gln P and Gln F groups than in the Gln 0 group. The bacterial number in PLF correlated with that in the liver. Neither the number nor the population of peritoneal exudative cells differed among groups. Plasma levels of proline, alanine and citrulline were significantly higher in the Gln P and Gln F groups than in the Gln 0 group. Both Gln supplemented groups showed significantly greater villous height, crypt depth, and numbers of mitoses per crypt in the small intestine than the Gln 0 group.

CONCLUSIONS

Supplemental Gln enhances peritoneal and hepatic bacterial clearance, regardless of Gln form. Gln-enriched may be more beneficial than Gln-depleted enteral diets in peritonitis.

Efficacy of different triglycerides in total parenteral nutrition for preventing atrophy of the gut in traumatized rats

BACKGROUND

The efficacy of different fat emulsions as components of a total parenteral nutrition (TPN) regimen on the integrity of the gut was assessed in traumatized rats. With the release of the short-chain fatty acids butyric or propionic acid during the hydrolysis of a structured triglyceride containing butyric acid (C4-L-C4-TG) or the beta-oxidation of nonanoic acid from trinonanoin (C9TG), respectively, the infusion of these two triglycerides was supposed to reveal positive effects against the TPN-induced atrophy of the intestine.

METHODS

After 3 days of fiber-free liquid diet, rats were traumatized (laparotomy) and catheterized. Afterwards they received equicaloric TPN that delivered 1008 kJ (241 kcal)/kg of body weight per day and 30% nonprotein calories as fat emulsion. The four fat emulsions tested in four groups of six animals contained either long-chain triglycerides (LCT), medium-chain triglycerides (MCT)-LCT (1:1), C9TG/LCT (1:1) or C4-L-C4-TG. Animals of a control group were infused with isovolemic 0.9% NaCl solution and were offered oral standard chow.

RESULTS

After 7 days of MCT/LCT administration, the mass-to-length ratio of the total small bowel as well as the masses of mucosa/submucosa and muscularis/serosa in 10-cm segments of the distal half of the small bowel were significantly higher than that found in the other TPN groups or not different from controls. Histometric measurement of the villus height in the ileum revealed no statistically significant differences from controls for the rats of the MCT/LCT and C4-L-C4-TG groups. In the colon, no statistically significant differences between TPN groups were found for either parameter.

CONCLUSIONS

Within the tested fatty substrates the MCT/LCT fat emulsion revealed less structural impairments in the distal half of the small bowel regarding mucosa/submucosa (mass and villus height), but also muscularis/ serosa (mass).

Glutamine

Glutamine is the most abundant free amino acid in the circulation. It is a primary fuel for rapidly dividing cells and plays a key role in the transport of nitrogen between organs. Although glutamine is absent from conventional regimens aimed at nutritional support, glutamine deficiency can occur during periods of metabolic stress; this has led to the reclassification of glutamine as a conditionally essential amino acid. Experiments with various animal models have demonstrated that the provision of glutamine can result in better nitrogen homoeostasis, with conservation of skeletal muscle. There is also considerable evidence that glutamine can enhance the barrier function of the gut. This review concludes by discussing the clinical evidence that supports the inclusion of stable forms of glutamine in solutions of nutrients.