Osmolite HN Research Articles

The In Vitro Effect of the Addition of Ion Exchange Resins on the Bioavailability of Electrolytes in Artificial Enteral Feeding Formulas

ObjectiveTo determine in vitro free ion concentration in 3 standard artificial enteral feeding formulas following the addition of ion exchange resins. MethodThree standard types of AEF were chosen: Osmolite HN®, Nutrison Standard®, and Isosource Standard®. The ion exchange resins used were: sodium polystyrene sulfonate and calcium polystyrene sulfonate. In a beaker were mixed 100mL of AEF with 1.5g or 3g of ion exchange resins for 48 hours at 37°C. Subsequently, the samples were precipitated and the supernatant obtained was used for determining the concentrations of calcium, magnesium, sodium, and potassium ions. ResultsThe addition of sodium polystyrene sulfonate to different types of enteral feeding formulas reduced the concentrations of potassium, calcium, and magnesium ions by 70%, 78.2%, and 77.6% in the case of Osmolite HN®; by 72.3%, 69.2%, and 63.5% in the case of Nutrison Standard®; and by 78.3%, 80.5%, and 74.5% in the case of Isosource Standard®. In contrast, the addition of calcium polystyrene sulfonate reduced the concentration of potassium and magnesium by 50.5% and 55.5% in the case of Osmolite HN®; by 49.8% and 43% in the case of Nutrison Standard®; and by 42.6% and 37.7% in the case of Isosource Standard®. ConclusionThe addition of ion exchange resins to different types of enteral feeding formulas, allows the in vitro free ion content of these to be reduced.

Gastric Residual Volume (GRV) and Gastric Contents Measurement by Refractometry

Traditional use of gastric residual volumes (GRVs), obtained by aspiration from a nasogastric tube, is inaccurate and cannot differentiate components of the gastric contents (gastric secretion vs delivered formula). The use of refractometry and 3 mathematical equations has been proposed as a method to calculate the formula concentration, GRV, and formula volume. In this paper, we have validated these mathematical equations so that they can be implemented in clinical practice. Each of 16 patients receiving a nasogastric tube had 50 mL of water followed by 100 mL of dietary formula (Osmolite HN, Abbott Laboratories, Columbus, OH) infused into the stomach. After mixing, gastric content was aspirated for the first Brix value (BV) measurement by refractometry. Then, 50 mL of water was infused into the stomach and a second BV was measured. The procedure of infusion of dietary formula (100 mL) and then water (50 mL) was repeated and followed by subsequent BV measurement. The same procedure was performed in an in vitro experiment. Formula concentration, GRV, and formula volume were calculated from the derived mathematical equations. The formula concentrations, GRVs, and formula volumes calculated by using refractometry and the mathematical equations were close to the true values obtained from both in vivo and in vitro validation experiments. Using this method, measurement of the BV of gastric contents is simple, reproducible, and inexpensive. Refractometry and the derived mathematical equations may be used to measure formula concentration, GRV, and formula volume, and also to serve as a tool for monitoring the gastric contents of patients receiving nasogastric feeding.

Assessment of intragastric pH value changes after early nasogastric feeding

Studies have suggested that early feeding after injury decreases morbidity and mortality. Few reports, however, have focused on the change in pH inside the stomach after early tube feeding. The aim of the present study was the assessment of 1) the change in intragastric pH after surgery, and 2) the effect of early nasogastric tube feeding on intragastric pH value. From April 1997 to February 1998, 80 patients who underwent colon resection for colorectal cancer by a single surgeon entered the study and were randomized into four groups. Twenty patients (group I) were kept on NPO for 1 wk, and 20 patients per group (groups II, III, and IV) were fed through a nasogastric tube from the second to the seventh postoperative day with low-residual (Osmolite HN), high-fat (Pulmocare), and glutamine-containing (AlitraQ) enteral formulas. Feeding started at 500 kcal/500 cc/d. If the patient tolerated the formula well, feeding increased to 1500 kcal/1500 cc −1/d −1 the following day. Intragastric pH was measured preoperatively and then twice daily until the sixth postoperative day. The pH value of intragastric juice increased significantly once feeding started (3.67 ± 1.33 on the third postoperative day; 4.28 ± 1.26 on the six postoperative day). The pH value seemed only mildly affected by the patient’s tolerance for tube feeding (poorly tolerated group, pH 3.52 ± 1.75 versus 3.75 ± 1.21 in the well-tolerated group on the third postoperative day; poorly tolerated group, pH 3.67 ± 1.02 versus 4.45 ± 1.27 in the well-tolerated group on the sixth postoperative day). The pH value of intragastric juice was higher in group II than in groups III and IV (4.51 ± 1.57, 3.90 ± 1.20, 4.42 ± 0.89 respectively, on the sixth postoperative day). This series suggests that early nasogastric feeding can significantly elevate the intragastric pH value in patients after resection of colorectal cancer. Nasogastric feeding may decrease the incidence of stress ulceration by elevating the pH value of intragastric juice.

Correlation of the Usage of Anti-Diarrheal Medications with Antibiotics and Other Medications in Tube Feeding Patients

LEARNING OBJECTIVE: To recognize the association of medications with the occurrence of diarrhea in the tube feeding population. The occurrence of diarrhea in the tube feeding patient population has been linked to medications. In clinical practice, the prescription of anti-diarrheal medications (ADM) are given based upon subjective reports from patients and/or caregivers. We prospectively gathered data on the usage of ADM, antibiotics, and other medications that have anti-motility, pro-motility, and cathartic effects to evaluate the correlation of drug treatments to the usage of ADM. There were 60 patients who were randomized to receive Criticare HN or Osmolite HN tube feeding. Data were analyzed on the 45 patients who were on tube feeding for a week after the target rate was achieved. Total tube feeding days was an average of 12 days. The results were as follows: ADM n = 18 No ADM n = 27 P-Value Antibiotic therapy 18 23 0.14 Cathartic and/or Pro-motility drugs 13 19 1.0 Anti-motility drugs 17 14 0.75 Criticare HN 9 11 0.56 Osmolite HN 9 16 0.56 Conclusion: It appears that antibiotic therapy does not necessarily result in the usage of ADM in hospitalized tube feeding patients. The need of ADM were not averted by drugs that have anti-motility effects. Further investigation is warranted on the diarrhea-causing effects of certain antibiotics.

Protein Quality of Enteral Nutrition products is Consistent with Label claims During Shelf life and Beyond Expiration Date

Objective Enteral formulas were monitored during their shelf life and beyond expiration date to examine protein quality. Design Protein quality was determined by protein efficiency ratio (PER) bioassays and amino acid analyses. Setting A certified laboratory performed the PER tests according to procedures established by the Association of Official Analytical Chemists and recognized by the US Food and Drug Administration (PDA). The amino acid analyses were performed in our laboratory using validated methods. Samples Commercially available formulas (Ensure, Osmolite HN, TwoCal HN) that contained protein blends of caseinates or caseinates with soybean protein isolate were studied. Main outcome measures Achievement of protein-quality values greater than or equal to 70% of the fresh reference casein value as determined by the PER method would be consistent with adequate protein quality as described by the FDA. Levels of indispensable amino acids that meet or exceed the standards established by the National Research Council of the National Academy of Sciences are considered high-quality proteins. Levels of amino acids throughout shelf life were compared with published label claims. Results Amino acid analyses, which included measurement of tryptophan and total sulfur amino acids, revealed that both fresh and outdated products met or exceeded standards for proteins of high biologic value and were consistent with label claims. The PER values ranged from 90% to 96% of the control diet for fresh product and 82% to 87% for products evaluated after expiration. Conclusion The enteral products studied provide high-quality protein throughout the shelf life of the product. J Am Diet Assoc. 1995; 95:46-52.

Effects of enteral feeding products on survival from Escherichia coli peritonitis.

Male Fischer 344 rats were orally fed one of four diets (Osmolite HN, Alitraq, Impact, and Purina rodent chow). After 6 days, jejunal mucosal nitrogen content and thickness were normal in all groups. After 7 days, challenge with Escherichia coli intraperitoneally demonstrated no difference in survival for any dietary group. In a second study, acute protein-calorie malnutrition was induced by administering 5% dextrose orally for 10 days. Animals were refed for 7 days with one of the four diets. Serum albumin concentrations and intestinal mucosal nitrogen content and thickness returned to normal with each refeeding program. Challenge with E. coli after 7 days of refeeding, however, again demonstrated no difference in survival for any dietary group. Specialized enteral feeding products, containing additional amounts of arginine, glutamine, glutamate, RNA, and omega-3 fatty acids, are no more effective than a standard enteral feeding product or rat chow in maintaining intestinal anatomy or restoring anatomy following fasting. Furthermore, we found no survival advantage for the specialized products following E. coli peritonitis.

Enteral Formula Composition Does Not Affect Response to Lethal Infectious Challenge in Mice

The effects of enteral formulations on the response of mice to infectious challenge with Listeria monocytogenes, influenza A or Candida albicans were studied to test the efficacy of specialized ingredients. CF-1 outbred female mice (12-15 g) were fed nonpurified diet (Purina No. 5002) or commercially available liquid formulas: Osmolite HN, Perative or Impact. There were no differences between the groups fed the liquid formulas with regards to mean survival time or percentage of survivors in any of these models of infection. Examination of spleens from the groups challenged with L. monocytogenes, lungs from mice infected with Influenza A and kidneys from the groups challenged with C. albicans revealed no differences in cure rate of survivors. Pre-feeding periods of up to 8 d before infection produced similar results for mice fed enteral formulations compared to nonpurified diet. Contrary to previous reports, the use of Impact did not improve resistance to disease in mice challenged with lethal doses of L. monocytogenes, as compared with mice fed Osmolite HN. Additionally, mice fed Impact, Perative, or nonpurified diet responded similarly to challenge with L. monocytogenes, C. albicans or influenza A. The results indicate that these acute lethal animal models of infectious challenge may be of limited use to distinguish effects of modified nutrient composition of enteral formulas.

Marked resistance of normal subjects to tube-feeding-induced diarrhea: the role of magnesium.

Because it is often assumed that feeding formulas are responsible for the diarrhea that commonly occurs in tube‐fed patients, the authors of this report sought to test the tolerance in normal subjects of a commonly used enteral feeding formula. They reasoned that if normal persons can tolerate substantial volumes of feeding without diarrhea, it may be patient‐specific factors and not the formulas themselves that cause diarrhea in sick persons. After five healthy male volunteers had undergone a 72‐hour acclimation to oral Ensure Plus (Ross Laboratories, Columbus, OH), the investigators administered Osmolite HN (Ross Laboratories) by continuous duodenal infusion, at progressively increasing infusion rates, until the subjects could no longer tolerate it.The subjects were able to tolerate maximum infusion rates of between 198 and 340 mL/h (5000 to 8650 kcal/ d). In two subjects, the infusion was stopped for symptoms other than diarrhea (abdominal distention, bloating, heartburn, and headache in one, and abdominal distention with vomiting in the other). These subjects never developed diarrhea, defined as >300 g of stool per day, despite maximum infusion rates of 371 and 258 mL/ h. The diarrhea that developed in the other three subjects was modest (350 to 380 g/d) and occurred only at infusion rates exceeding 275 mL/h, or more than 400% of their estimated basal energy expenditures.Blood and stool samples were analyzed to elucidate the mechanisms causing the diarrhea. The magnesium content of pooled diarrheal stools was significantly greater than that of nondiarrheal stools, suggesting that the magnesium load (mean 89 mmol/24 h, or more than 6 times the typical intake for US men) may have been the causal factor. There was no evidence that unabsorbed fat, carbohydrate, or protein contributed to the diarrhea.

Marked resistance of normal subjects to tube-feeding-induced diarrhea: the role of magnesium

The tolerance of healthy subjects to increasing rates of tube feeding was studied to better understand the etiology of diarrhea among tube-fed patients. Five volunteers were fed Osmolite HN by continuous duodenal infusion beginning at 314 kJ (75 kcal).kg body wt-1 x d-1 and progressing each 24 h until no longer tolerated. The five subjects were able to tolerate maximum 24-h infusions of 331-511 kJ.kg-1 x d-1 (198-340 mL/h). Diarrhea developed in only three subjects. Compared with nondiarrheal stools, the high-speed supernatant of the diarrheal stools had significantly higher concentrations of magnesium (192 +/- 22 mmol/L vs 139 +/- 17 mmol/L, P = 0.005), lower concentrations of potassium and phosphorus, and similar concentrations of calcium. The mean carbohydrate, fat, and nitrogen contents were not significantly different. We conclude that normal adult males are remarkably tolerant to duodenal infusion of this typical, isotonic tube-feeding product. The diarrhea that occurred in three of the volunteers at very high infusion rates appeared to be osmotic and attributable predominantly to magnesium.

The Effect of Duodenojejunal Alimentation on Gastric pH and Hormones in Intensive Care Unit Patients

We evaluated effects of duodenojejunal (DJ) feeding on gastric pH and selected gastrointestinal hormones in 13 randomly selected patients in an intensive care unit (ICU). To obtain baseline values for gastric pH, a nasogastric (NG) tube was placed in each patient and gastric pH was measured every 30 minutes for 2 hours. To obtain control values, a Dobbhoff tube was placed fluoroscopically and 0.45 percent saline solution (NaCl), 75 ml, was infused for 1 hour and gastric pH was measured again; the previously placed NG tube was left in position. Then, by randomization, either 0.45 percent NaCl (pH = 5) was continued (n = 6) or a high-nitrogen, isotonic, enteral feeding solution (Osmolite HN, pH = 6.4) (n = 7) was infused, both at 75 ml/h. Gastric pH was noted hourly for 96 hours; antacid (Maalox TC, 15-ml aliquots) was given by NG tube when the pH was 4 or less. After 96 hours, the infusion was stopped and gastric pH was noted for 4 additional hours. Before and during initial saline solution infusion; after 24, 48, 72, and 96 hours of continuous infusion; and 4 hours after stopping the infusion, peripheral venous blood was obtained for measurement of plasma gastric inhibitory polypeptide (GIP) and serum gastrin. Data were analyzed by ANOVA (RMD), Fishers' exact test, and the unpaired t-test. Groups did not differ demographically. Throughout the infusion, gastric pH tended to be higher with the enteral feeding solution than with saline solution, but this was significant only at 24 hours. Less antacid was required with the enteral feeding solution at 24 and 48 hours than with saline solution. Plasma GIP levels were significantly higher with the enteral feeding solution than with saline solution during most of the infusion. Serum gastrin levels did not differ between the groups. In this cohort, infusion of the enteral feeding solution tended to maintain a gastric pH of more than 4 and was associated with increased plasma GIP levels, which may inhibit gastric acid secretion. Early enteral feeding may benefit certain ICU patients.

Effect of Enteral Diets on Whole Body and Gut Growth in Unstressed Rats

The composition of enteral feeding formulas may have different effects on total body and gut growth. We studied the growth effects in rats of a complex solid fiber-based diet (Prolab Rodent Diet) with that of three isocaloric and isonitrogenous commercially available liquid feeding formulas which differ in their type of protein (Osmolite HN, an intact protein formula; Reabilan HN, a peptide formula; and Vivonex-TEN, an amino acid formula). Total body weight gain was greatest with the rodent diet (93 +/- 2 g/10 days), followed by the peptide diet (72 +/- 5 g/10 days) and intact protein diet (58 +/- 8 g/10 days). Weight gain was significantly lower on the amino acid diet (43 +/- 7 g/10 days). Proximal and mid gut mass was comparable with all four diets, but distal gut mass was significantly lower with the amino acid diet. Somatomedin C levels on the rodent diet (13.3 +/- 1.8 nM), and the peptide diet (14.0 +/- 3.3 nM) were significantly higher than somatomedin C levels on the amino acid diet (8.0 +/- 1.0 nM). Somatomedin C levels on the intact protein diet (9.6 +/- 1.4 nM) were intermediate between the rodent diet and amino acid diet. We conclude that growth effects vary with different enteral diets (unrelated to total calories and protein) and may result from differences in the generation of tissue growth factors.

Visceral Protein Levels in Trauma Patients Are Greater with Peptide Diet Than with Intact Protein Diet

Early enteral nutrition may preserve gut function and prevent bacterial translocation after trauma. Standard enteral nutrition uses products which contain intact protein and require digestion for absorption. Peptide-based enteral nutritional products are better absorbed and stimulate the release of gut trophic hormones. This study was performed to determine whether a peptide-based (PEP) product (Reabilan HN) was better tolerated and/or produced better hepatic protein responses in patients after trauma when compared to an intact-protein (PRO) formula (Osmolite HN). Eighteen trauma patients were prospectively randomized to PEP (n = 9) or PRO (n = 9) enteral diets administered via nasoduodenal tubes (within 1-2 days of injury). Visceral protein synthesis was assessed by measuring baseline and 1 week pre-albumin and transferrin levels. Diarrhea was defined as greater than 300 gm/day of stool. Groups were similar in age, Injury Severity Score (ISS), caloric intake, and protein intake. Protein levels increased significantly faster in PEP patients despite similar urea nitrogen excretion. Diarrhea developed in four (44%) PRO patients and none of the PEP patients. Three of the PRO patients were switched to PEP after one week and diarrhea subsided in all three patients. Peptide-based enteral diets are associated with better hepatic protein responses and less diarrhea compared to intact-protein diets.

Effect of heat processing and storage on protein quality and lysine bioavailability of a commercial enteral product

Several rat bioassays were conducted to evaluate protein quality and lysine (LYS) bioavailability (BIO) of Osmolite HN, a commercial enteral product, as affected by the severity of heat processing during sterilization and by storage of the products for 1 year. Without amino acid supplementation, the protein quality of Osmolite HN, as determined by protein efficiency ratio (PER), was lower than that of casein, regardless of heat treatment. With addition of the limiting amino acid, cystine, the PER of Osmolite HN was equivalent to that of cystine-fortified casein. Storage of the product for 1 year had no effect (p greater than 0.05) on PER, even though the products had darkened in color. Slope-ratio regression analysis (weight gain regressed on supplemental LYS intake) yielded a LYS BIO estimate of 94.4% for the Osmolite HN control relative to crystalline LYS. Partitioning weight gain into that resulting from LYS consumed in the basal diet and that resulting from the LYS supplement per se provided more accurate estimates of LYS BIO. This method estimated LYS BIO at 100% for the Osmolite HN products, regardless of heat treatment. With storage, LYS BIO decreased 11-12% in all of the Osmolite HN products. The decreased LYS BIO is of minimal nutritional significance in that overall protein quality of the products was not affected by storage. This is likely due to the fact that there is a plethora of lysine in Osmolite HN such that LYS is not a protein-quality limiting factor.