Bolus Feeding Research Articles

Consultation with the Specialist

1. Maria-Stella Serrano, MD* 2. Elizabeth E. Mannick, MD* 1. *Division of Pediatric Gastroenterology and Nutrition, Department of Pediatrics, Louisiana State University Health Sciences Center, New Orleans, LA After completing this article, readers should be able to: 1. List the indications for enteral nutrition. 2. Describe the techniques used for enteral nutrition. 3. Discuss the advantages and disadvantages of gastric and jejunal feedings. 4. Name the types of formulas available. 5. Identify the complications of enteral nutrition. An 8-year-old girl presented to the emergency department after suffering severe facial trauma and a severe closed-head injury that caused a displaced skull fracture with the subsequent development of a subdural hematoma. The girl underwent surgery for drainage of the hematoma and fixation of the facial fractures. During her immediate postoperative period, she required ventilatory assistance and a central line placement for secured intravenous access. Parenteral nutrition was started at this point. During recovery, her neurologic status remained significantly impaired. A rehabilitation program was started, a nasogastric (NG) tube was placed, and enteral feedings with an intact protein formula were administered continually through a pump. The caloric density of the formula was adjusted to what she was receiving parenterally. Initially, the patient received a small volume enterally, which was increased as she tolerated it. Simultaneously, parenteral nutrition was decreased accordingly. The patient tolerated the weaning process well and soon was on full enteral feeds. Additional medications, including anticonvulsants, were administered through the NG tube. Bolus feedings were attempted during the day and continuous feedings during the night, which she tolerated well. At this point, due to her neurologic status, the option of a gastrostomy was discussed with her parents as a temporary supportive measure through the rehabilitation process. A percutaneous endoscopic gastrostomy (PEG) was placed with no complications. The patient was discharged from the hospital to continue her rehabilitation process at home, with intensive physical and occupational therapy and home enteral nutrition (HEN). Two weeks after discharge, the patient came to the emergency department due to …

Multipoint measurement of intragastric pH in healthy preterm infants

Background: The diagnostic use of 24 hour oesophageal pH monitoring in infants is controversial because of the impact of feed buffering of gastric acidity. Aim: To re-evaluate the effect of...

Risk factors for aspiration.

There are numerous risk factors for aspiration in tube-fed critically ill patients. However, there is confusion about the extent to which these factors actually contribute to aspiration. The purpose of this literature review was to summarize findings from selected research studies. A nonexhaustive literature search was conducted to identify risk factors for aspiration in tube-fed, critically ill patients. The most commonly cited factors were decreased level of consciousness, supine position, presence of a nasogastric tube, tracheal intubation and mechanical ventilation, bolus or intermittent feeding delivery methods, high-risk disease and injury conditions, and advanced age. Many studies of aspiration risk factors have relatively small sample sizes and used equivocal definitions of aspiration. Although some addressed aspiration as an outcome, others considered gastroesophageal reflux or pneumonia as outcomes. Despite these variations, authors almost uniformly agree that a decreased level of consciousness and a sustained supine position are major risk factors for aspiration. There is less agreement regarding the effect of a nasogastric tube (or its size) on aspiration and on the effect of various formula delivery methods. A decreased level of consciousness is a major risk factor for aspiration, as is a sustained supine position. Although some authors favor using small-bore feeding tubes to prevent aspiration, there seems to be insufficient data to warrant this action. Although strong data are lacking regarding feeding delivery methods, there are more data to support continuous feedings than bolus/intermittent feedings in high-risk patients.

Tolerability of bolus versus continuous gastric feeding in brain-injured patients

Brain injured patients may exhibit altered gastric emptying; thus, some believe post-pyloric feeding to be tolerated better than gastric feeding. Reliable post-pylorus access can be difficult to obtain, so gastric feeding remains the preferred route for administering nutrition. Feeding intolerance may be associated with increased complications and costs. We sought to compare bolus (B) versus continuous (C) gastric feeding in brain injured patients. This retrospective cohort study was carried out at a neurological/neurosurgical intensive care unit at a Level 1 trauma and tertiary referral center. Our subjects were 152 consecutive patients over two years. Use of B or C feedings was based on clinicians' preferences. Abdominal examination and gastric residuals (>75 mL over four hours) defined feeding intolerance (FI). Putative risks for FI were compared between the groups. Demographic characteristics were similar between groups B (n = 86) and C (n =66). Feeding intolerance occurred more often in group B than in group C (60.5% vs. 37.9%, p =0.009). Group C patients achieved 75% of nutritional goals faster than group B patients (median 3.3 vs. 4.6 days; p =0.03). Prokinetic agent use was similar between the groups and did not reduce the time to achieve nutritional goals. There was a trend towards a reduction in the incidence of infections in group C (p =0.05). Independent predictors of FI included: sucralfate (OR 2.3), propofol (OR 2.1), pentobarbital (OR 3.9) or paralytic (OR 3) use; older age (OR 5); days receiving mechanical ventilation (OR 1.2); and admission diagnosis of either intracerebral hemorrhage (OR 2.2) or ischemic stroke (OR 1.9). Continuous gastric feeding is better tolerated than B feedings in patients with acute brain injuries. Use of prokinetic agents did not affect time to achievement of nutritional goals. Use of common medications including sucralfate and propofol were associated with FI. [Neurol Res 2002; 24: 613-620]

Feeding the ill or preterm infant.

Illness and immaturity often interfere with a neonate's ability to receive full enteral feedings during the first week of life. The goals of feeding in the NICU are to nourish the preterm infant for appropriate growth and development and to facilitate the earliest possible discharge from the NICU. Early, small-volume feedings, or trophic feedings, have been studied as a method for achieving these goals. The high-risk infant given such trophic feedings not only receives minimum enteral nutrition, but also attains earlier full nutritional feedings and, consequently, is discharged home earlier. Oro- or nasal-gastric gavage feedings are usually indicated for this group of infants because of their physiologic immaturity and the frequent presence of respiratory illness. Recent studies support the use of intermittent bolus feedings, which have long been used for the premature infant. Several authors have noted advantages to continuous infusions as well. Because the infant is unable to pace or refuse gavage feedings, the caretaker must determine the appropriate volume of each feeding. The optimal volume for initiation and advancement of trophic and nutritional feedings is still under investigation, but reports have demonstrated safe volumes for even the extremely premature infant.

The Limitations of Using Gastric Residual Volumes to Monitor Enteral Feedings: A Mathematical Model

A variety of methods are used to estimate whether a gastric residual volume is excessive during enteral feedings. In this study, mathematical models of gastric volume during continuous or bolus feedings were developed to evaluate the relevance of measuring residual volumes. The validity of common threshold values of residual volumes that are used to monitor the safety of enteral feeding in infants and adults was tested. A mathematical representation of gastric volume was established using standard integration methods. Assuming an exponential rate of gastric emptying, continuous feedings result in a steady state volume that is proportional to the half‐emptying time of the stomach and the rate of addition of endogenous and exogenous fluids. During bolus feedings, a steady state volume will be achieved that is proportional to the volume of the bolus and a rate constant calculated using the half‐emptying time and the bolus interval. Based on these models, it can be predicted that threshold values commonly used to monitor feedings do not accurately predict residual volume. In both infants and adults, the threshold values often will overestimate residual volumes at shorter half‐emptying times and underestimate residual volumes at longer half‐emptying times. Because of the complex relationship between infusion volume, gastric emptying, and gastric volume, evaluation of the volume of gastric contents is an unreliable method for monitoring feeding tolerance.

Enteral feeding in infants <1250 g starting within 24 h post-partum

Establishing enteral feeding in the very low birth weight infant as soon as possible after birth has been shown to promote growth and reduce the need for intravenous lines. Human milk can be administered either as a continuous infusion or as intermittent boluses. The aim of this study was to investigate the effect of continuous versus bolus feeding on gastrointestinal tolerance, time to reach 120 ml/kg, 150 ml/kg and full enteral feeding, regain birth weight, duration of intravenous lines, incidence of septicaemia, persistent ductus arteriosus and necrotising enterocolitis. A retrospective analysis of hospital records was performed. Infants with a birth weight < 1250 g born during a 12-month period at Aker and Ullevål University hospitals in Oslo, who survived the first 21 days, were included in the study. A Total of 49 infants (25 continuous and 24 bolus) fulfilled the entry criteria and data from these infants were analysed. Enteral feeding volumes (120 ml/kg, 150 ml/kg and full) were attained significantly faster with continuous feeding (7 versus 12 days, 8 versus 14 days, 9 versus 12 days). Consequently the bolus group had a significantly longer duration of intravenous lines (14 versus 9 days). There were no differences regarding time to regain birth weight, the incidence of septicaemia, persistent ductus arteriosus or necrotising enterocolitis. infants of birth weight < 1250 g can be fed breast milk already from the 1st day of life and achieve full enteral feeds faster than previously reported even in more mature infants. Full enteral feeds are attained faster with continuous versus bolus feedings and continuous feeding therefore results in shorter need for intravenous fluids.

Leptin levels in preterm human breast milk and infant formula.

Leptin, a hormone present in breast milk, is involved in energy regulation and metabolism. The purpose of this investigation was to determine whether leptin is present in either preterm breast milk (PBM) or preterm formula (PF). The effects of delivery methods and pasteurization on leptin levels also were evaluated. PBM samples were obtained from 29 mothers who delivered infants at between 23 and 34 weeks' gestation. Leptin levels were measured in PBM and PF with the use of a radioimmunoassay specific for human and bovine leptin, respectively. Milk samples were pasteurized by fast- and slow-heating methods. PBM and PF spiked with human leptin were delivered through catheters by bolus and continuous administration to determine the effects of delivery method on recoverable leptin levels. Median PBM leptin concentration was 5.28 ng/mL (intraquartile range: 24.79). Birth gestational age, birth weight, and gender of the infant did not significantly influence PBM leptin levels. Neither bolus nor continuous feeding practices affected leptin levels in PBM or spiked PF. However, pasteurization significantly reduced the amount of detectable leptin in PBM. PBM leptin levels were highly variable and similar to levels reported for term breast milk. There was no effect of postnatal age on PBM leptin concentrations. Sterilization decreased detectable leptin levels, whereas feeding practices had no adverse effect on the quantity of leptin delivered. Although no infant formula contained leptin, leptin could be added to formula and delivered through various feeding methods without loss.

Secretion of Trophic Gut Peptides Is Not Different in Bolus- and Continuously Fed Piglets

In neonates, bolus feeding is associated with greater rates of intestinal growth than is continuous feeding. We tested whether the concentrations and secretion rates of trophic gut peptides are higher in bolus-fed than in continuously fed piglets. Five 21-d-old piglets were surgically implanted with gastric, arterial and portal catheters and a portal blood flow probe. At postnatal d 30 and 31, pigs received an equal amount of primed continuous or bolus feeding of a cow's milk formula in a randomized, crossover design. During a 6-h period, portal blood flow and arterial and portal concentrations of glucagon-like peptide-2 (GLP-2), peptide YY (PYY) and gastric inhibitory polypeptide (GIP) were measured. All hormone levels were significantly increased within 1 h of the start of the experiment, independent of the feeding modality. There were no differences between bolus and continuous feeding in either the arterial concentrations or secretion rates of GLP-2, PYY and GIP. In both treatment groups, the increases in the plasma concentrations of GLP-2 and GIP after feeding were substantially greater than those for PYY. We conclude that the production or circulating concentrations of GLP-2, PYY and GIP are not significantly different in bolus- and primed continuously fed piglets.

Limited approach to the right flank for placement of a duodenostomy tube.

A new enterostomy tube placement technique is described for provision of nutrients into the duodenum. Placement of the duodenostomy tube (d-tube) is performed through a limited right flank approach under sedation and local anesthesia. Seven client-owned animals (three dogs and four cats) requiring enteral nutritional support were selected for d-tube placement. Patients were fed via the d-tube for two to 28 days. Complications included discomfort when manipulating and exteriorizing the duodenum, discomfort with bolus feedings, local cellulitis, and tube site infection. All complications resolved without further incident. This technique should be considered in patients that are not good candidates for prolonged general anesthesia or esophageal or gastric feeding, or patients being mechanically ventilated.

Feeding Tolerance in Preterm Infants: Randomized Trial of Bolus and Continuous Feeding

Objective: To test the hypothesis that continuous gastric infusion (CGI) is better tolerated than intermittent gastric bolus (IGB) in small very low birth weight (VLBW) infants.Design: Two-center, prospective, randomized, unmasked clinical trial.Patients: 28 VLBW infants (birth weight <1250 g). A strict feeding protocol was followed.Intervention: Patients were randomized to IGB or CGI.Main outcome measures: Time to reach full feeds (160 cc/kg/d)(by design and real), daily weight, caloric intake, residual gastric volume and type of feeding (formula vs. human milk vs. both).Results: Five infants failed to complete the study because of death (n = 4) or protocol violation (n = 1). The two groups did not differ by birth weight or gestational age; infants fed via IGB reached full feeds earlier (p = 0.03) and had less delay in reaching full feeds than infants fed via CGI.Conclusion: Contrary to our hypothesis, gravity IGB is more effective than CGI in improving feeding tolerance in small VLBW infants.

Bolus ornithine and arginine-ketoglutarate supplementation in distal intestine after 65% resection in rats

Introduction: Enteral feeding has been reported to increase intestinal mucosa proliferation after resection. Dietary components influence the intestinal adaptive response. The purpose of this study was to evaluate the effect of ornithine- (OKG) or arginine-ketoglutarate (AKG) bolus supplementation on intestinal postresectional adaptation in the rat. Methods: Male Wistar rats underwent 65% small-bowel resection and received either OKG 3 g/kg/day, isonitrogenous AKG or saline by gavage once daily. The animals had free access to rat chow. Sampling was done 10 days after resection. Fed animals without surgery or specific treatment served as controls. Results: Mucosal wet weight, DNA, RNA, protein content and sucrose activity of the mucosa, as well as villus height were significantly increased in all resected animals compared to controls. No significant differences in body weight or intestinal adaptation could be found between the three dietary groups. Conclusion: Postoperative enteral bolus feeding supplemented with OKG or AKG did not significantly enhance the adaptation of the remnant small bowel 10 days after massive intestinal resection when rats had free access to rat chow.

Microbial contamination of enteral feeding formulas and diarrhea

Twenty-five medical and surgical patients receiving liquid ready-to-use sterile enteral formulas were evaluated prospectively to investigate the relation of diarrhea to serum albumin level, total lymphocyte count, delayed hypersensitivity to purified protein derivative, antibiotic therapy, administration rate and site of enteral formula, and microbial contamination of enteral feeds. Formulas were administered to 6 patients with hang times of up to 6 h by pump-assisted continuous drip and to 19 patients with hang times of up to 3 h as a bolus feeding. Samples of formulas for microbial culture were obtained aseptically before and after feeding on the first and eighth day of the study period. The incidence of microbial contamination of the formula before and after feeding was 1 of 49 samples (2.0%) and 10 of 48 samples (20.8%), respectively. There were 2 patients with diarrhea, which occurred on the second day. Formula samples from 2 patients (100%) with diarrhea and 2 samples from 23 patients (8.7%) without diarrhea were contaminated with 10 4 cfu/mL or more, respectively. A significant difference ( P = 0.04) was detected between the two groups. The other factors studied showed no significant association with the incidence of diarrhea. In conclusion, contaminated formula appears to play a significant role in the etiology of diarrhea in patients receiving enteral feeding.

Clinical Observations: Orogastric Enteral Feeding: An Alternative Feeding Access

In patients who are unable to consume adequate nutrients orally, enteral feeding is the preferred route of nutrition support. This may include nasogastric, gastrostomy, and, less commonly, the jejunostomy routes. The former may be difficult for those patients with rhino‐sinusitis problems and for those with an aversion to tube passage via the nostril, and the latter two are surgically invasive. At our Cystic Fibrosis Center, the orogastric route has also been used for nocturnal nutrition support. To date, the orogastric feeding route has been beneficial and well received by 15 patients whose age at the initiation of feedings ranged between 11 and 24 years. The actual technique of tube placement is simple and similar to that of nasogastric tube insertion. A French silastic feeding tube is inserted nightly into the stomach via the mouth in a manner similar to that of nasogastric tube insertion. It can be used for both continuous and intermittent bolus feedings. In our experience, orogastric feedings allow for successful nutrition intervention in those who are unsuccessful with oral supplements. In addition, this method helps to avoid the problems that are frequently associated with nasogastric and other invasive tube feeding maneuvers.

Respiratory sinus arrhythmia during feeding: a measure of vagal regulation of metabolism, ingestion, and digestion in preterm infants.

Respiratory sinus arrhythmia (RSA), a non-invasive indicator of vagal regulation of the heart, and heart period (HP) were monitored before, during, and after oral or gastric-tube bolus feedings in 32 preterm infants. Group 1 infants (n=15) were < or =30 weeks gestational age (GA) at birth (mean 28.3 weeks) and group 2 infants (n=17) were > or =31 weeks GA at birth (mean=33.2 weeks). Mean postmenstrual ages at the time of study were 33.5 +/- 2.3 (SD) weeks in group 1 and 33.9 +/- 1.6 (SD) weeks in group 2. RSA and HP decreased in both groups during feeding. However, postfeeding RSA and HP increased toward prefeed levels only for group 2 infants. In addition, RSA and HP changes during feeding were correlated only for group 2 infants. The results suggest that the preterm infant may experience a maturational lag in vagal function and in the influence of vagal activity on metabolic mechanisms (i.e. heart rate) related to ingestive needs. This maturational lag may contribute to continued feeding difficulties and may be a measurable marker of subtle neurodevelopmental problems.

Neonatal Necrotizing Enterocolitis: Possible Role of Probiotic Supplementation

Neonatal Necrotizing Enterocolitis: Possible Role of Probiotic Supplementation

Esophagogastric disconnection for gastroesophageal reflux in children with severe neurological impairment

Purpose: Fundoplication has been used successfully to treat gastroesophageal reflux in the pediatric population; however, the results are poorer in those children with neurological impairment. We propose an alternative approach to the needs of these special patients and report the use of esophagogastric disconnection to control reflux in children with profound neurological impairment. Methods: Between 1991 and 1997, 27 esohagogastric disconnections were performed. All patients were severely neurologically impaired with symptomatic gastroesophageal reflux confirmed by an upper gastrointestinal radiographic study. There were 16 boys and 11 girls with ages ranging from 6 months to 40 years. Three had undergone previous fundoplications that failed, whereas the remaining underwent esophagogastric disconnection as a primary antireflux procedure. Follow-up ranged from 1 month to 6.3 years (average, 2.8 years). The operative approach used a midline incision. The gastroesophageal junction was divided, and the gastric side was closed. A 30- to 40-cm jejunal limb was prepared for Roux-en-Y reconstruction and brought up to the esophagus in a retrocolic manner. Esophagojejunal and jejunojejunal anastomoses were then performed. A Stamm tube gastrostomy was placed, and the appendix was removed. A pyloroplasty and tube jejunostomy were performed when felt to be clinically indicated. Results: Gastroesophageal reflux symptoms resolved, and bolus feedings were tolerated by all patients. Oral feedings were tolerated except in those children limited by their swallowing abilities. Early postoperative complications occurred in eight patients (30%) with two (7%) requiring reoperation (esophageal leak and enterocolitis). Late reoperation was necessary in four patients (15%) for small bowel obstruction, paraesophagcal hernia, gastrostomy revision, and enterocolitis. There were no perioperative deaths, but three patients (11%) died of late surgical complications (two of small bowel obstructions, and one of improper reinsertion of a gastrostomy tube). Three other children died of unrelated causes. Conclusions: Esophagogastric disconnection effectively eliminates gastroesophageal reflux while allowing both bolus tube feedings and oral supplementation. This operation provides an alternative method of controlling gastroesophageal reflux in children with profound neurological impairment.

O.09Impact of bolus feeding via nasogastric tube onappetite and food intake in humans

O.09Impact of bolus feeding via nasogastric tube onappetite and food intake in humans

Slow infusion feedings enhance duodenal motor responses and gastric emptying in preterm infants

It is unknown whether it is better to feed preterm infants intragastrically by bolus or continuous infusion. This study compared the effect of 2 feeding rates on antral and duodenal motor responses and gastric emptying. Continuous perfusion manometry with a low-compliance machine was performed in 22 infants given feedings at 2 infusion rates. Gastric emptying was also assessed by using a dye-dilution technique to determine whether changes in motor response were reflected by changes in function. The number of antral contractions with both feeding rates decreased from that seen during fasting. Duodenal motor responses increased when infants were fed by slow infusion and decreased when they were fed by rapid infusion. Infants emptied 12 mL/kg of a 20-mL/kg feeding by 20 min after completion of the feeding given by slow infusion concomitantly with the increase in duodenal motor activity but only 8 mL/kg by 20 min after completion of the bolus feeding, when duodenal motor activity decreased (P < 0.01). Two hours after completion of the feeding, volumes remaining in the stomach after slow infusion were one-ninth those remaining after bolus feeding. When preterm infants are fed by slow infusion over 120 min, their duodenal motor responses are more like those observed in adults and their gastric contents are emptied faster and more completely than when they are fed with a rapid bolus. Am J Clin Nutr 1998;68:103–8.

Effect of feed interval and feed type on splanchnic haemodynamics

AIMTo study the effect of enteral feeding on splanchnic blood flow velocity in preterm infants.METHODCoeliac axis and superior mesenteric artery (SMA) blood flow velocity were measured longitudinally in a cohort...