Synopsis  

Enteral access provides the platform for physiological nutritional therapy. Enteral feeding improves epithelial structure and function, enhances mucosal immunity, and allows rapid advancement of feeding. Considering the available data and our clinical experience, enteral nutrition should be used instead of parenteral nutrition whenever possible, since it is more cost-effective and likely safer. This contribution reviews the currently available endoscopic techniques for enteral access, their indications and contraindications. Details of postprocedure management and feeding regimes are discussed. Further studies will refine precise indications and methods.

 Introduction   

The past forty years have shown tremendous improvement in the ability to deliver nutrition to patients at risk. Parenteral nutrition was introduced in the 1960s and has continued to be an important tool in patients with gastrointestinal impairment [1]. However, enteral feeding, as opposed to parenteral nutrition, improves epithelial structure and function, enhances mucosal immunity, and allows rapid advancement of feeds [2,3]. Considering the available data, enteral nutrition should be used whenever possible as it is proven to be more cost-effective and likely safer [3,4].

Benefits of nutrition support   

Nutritional support is widely used for several reasons. There is a definite association between malnutrition, common in hospitalized patients, and increased morbidity and mortality. Intuitively, well-nourished patients will respond favourably to treatment. In some situations, however, weight gain, survival, or improvement in functional status may be unrealistic goals. In patients with terminal diseases, maintaining or improving a patient's health-related quality of life, reducing pain and suffering, and providing an access for hydration or medication may be obtainable, reasonable short-term goals. However, the plethora of relatively small, retrospective, uncontrolled trials focusing on various patient populations have made it difficult to develop guidelines based on solid evidence. These guidelines will need to incorporate reasonable goals and objectives [4].

Enteral access   

Enteral feeding can be provided by transnasal tubes, or by direct percutaneous access into the stomach or jejunum.

Surgical gastrostomies and jejunostomies have now largely been replaced by percutaneous endoscopic approaches since the initial description by Gauderer and Ponsky in 1980. Endoscopic techniques have been shown to be cheaper than the surgical approach. Since that time, a multitude of commercial kits, techniques, and advances in the development of specialized enteral nutrition feeding products have created interest in the development of disease-specific nutritional management [5,6].

It is our objective to review the various methods of enteral access by considering each of their indications and contraindications, any technical variations, and postprocedural management and complications. With this approach, the correct method of enteral access may be chosen on an individualistic basis.

 Gastric or enteric feeding?   

Bedside placement of a nasoenteric tube is the most common enteral access technique used in hospital and long-term care settings [7]. Nasoenteric tubes are designed to deliver nutrition into the stomach or into the jejunum. The choice should be determined by patient comorbidities, anticipated tolerance of tube feedings, and the risk for aspiration.

 Nasogastric (NG) feeding   

Nasogastric tubes are generally placed when enteral nutrition is anticipated for 30 days or less [7]. Nasogastric tubes are best avoided if the patient has gastric outlet obstruction, gastroparesis, prior surgery of the foregut, GERD, and a risk to aspirate [8,9]. In these cases, a nasojejunal tube should be placed.

NG tube placement   

Typically, an 8-12 French nasogastric tube is passed into the stomach after the tube has been lubricated, the head has been flexed, and the patient ingests sips of water to assist the passage of the tube into the stomach [10]. Beside auscultation can be misleading as inappropriate tube locations, such as in the lung, pleural cavity, or esophagus may be misinterpreted to be in the proper position. Therefore, every patient should have a radiograph confirming proper tube position prior to initiation of tube feeds [11].

For patients who are comatose and cannot cooperate by swallowing, the tube is passed directly after lubrication, and head flexion. Its position is checked by auscultation and a radiograph [1].

NG tube management   

Nasogastric feeding tubes should not be maintained for more than 30 days because of their inherent associated complications. They can be used for feeding, administering medications, and for gastric decompression. When these tubes are being used for feedings and medication administration, the patient should be elevated in bed at an angle of greater than 30 degrees to avoid the risk of aspiration.

NG tube complications   

Because NG tubes have to be relatively small (to be tolerated), they are prone to displacement, kinking, clogging, and early removal [7]. The most common mechanical complications are nasopharyngitis, sinusitis, and otitis.

 Nasojejunal (NJ) feeding   

Nasojeunal tube feeding is preferred over nasogastric feeding in patients with gastroparesis, and those who have undergone gastric surgery. Nasojejunal feeding has been shown to reduce the risk of pulmonary aspiration.

Technique   

A number of techniques have been employed for bedside placement of a nasojejunal tube.

Different tubes   

Thurlow et al. used a stylet-filled tube with a corkscrew motion [13]. This technique was confirmed by Zaloga who achieved greater than 90% success in tube passage [14]. Lord et al. promoted the use of unweighted feeding tubes as their success rate was 92% compared to 56% for weighted tubes [15]. Ugo et al. placed the patient in the right lateral decubitus position and tracked the nasojejunal tube into proper position by auscultation [16]. Most clinicians have not experienced the success rates for adequate passage of nasojejunal tubes given in the reported literature.

Prokinetics   

Results have been mixed when attempting to position a tube beyond the pylorus with the use of prokinetic agents. For example, Selfert et al. and Kittinger et al. reported no benefit with the assistance of metoclopramide for nasojejunal tube placement (17,18). However, Whatley et al. and Kalafarentzos et al. did note a 90% success rate with the use of metoclopramide [19].

Fluoroscopy or endoscopic assistance   

Failure to pass a nasoenteric tube at the bedside requires the use of fluoroscopy or endoscopy. Success of nasojejunal tubes with fluoroscopic guidance can approach 100% [5]. However, endoscopy is preferred in those centres without bedside fluoroscopic capabilities as transport of critically ill patients may be time-consuming, expensive, and dangerous.

The drag technique   

The most common technique for endoscopic passage is the 'drag' technique. This is performed when a feeding tube is pulled into the jejunum by grasping a suture tied to the end of the tube with alligator forceps. More successful techniques involve the use of a guidewire. After the tube is placed into the stomach under direct visualization with the endoscope, a guidewire is passed through the distal end of the feeding tube and grasped with a snare or forceps. The guidewire is dragged into the small bowel with the endoscope and grasping device. By maintaining tension on the guidewire, the feeding tube is pushed into position [1]. Patrick et al. reported a 94% success rate using this technique [20].

Through the scope passage   

Finally, large channel endoscopes allow passage of an 8 Fr or 10 Fr jejunal tube directly through the biopsy channel [21]. The proximal end of the tube is backloaded from the oral cavity into the nasal cavity using a nasal transfer tube

NJ tube management   

Nasojejunal tubes are smaller than nasogastric tubes and are therefore more prone to kinking and clogging. Ten to 12 French gauge tubes should be used when possible [21]. The tubes should be flushed after every feeding or instillation of medication. Only liquid preparations of medications should be placed through these tubes. The use of supplemental protein in a tube feeding or an immune-enhancing formula can promote obstruction [1]. Also, certain medications such as theophylline or potassium chloride may coagulate the tube feedings and obstruct the nasojejunal tube [1].

NJ tube feeding complications   

The complications for nasojejunal tube placement are similar to those for nasogastric tubes. All transnasal placements carry a risk of sinusitis and nasopharyngeal lesions [1].

Bronchial misplacement   

The risk of inadvertent tube misplacement in the lung is greatest in comatose patients who can not assist in the placement, and who may not cough with bronchial insertion of a nasoenteric tube. Some have suggested measuring the tube's length from the earlobe to the aphoid process prior to insertion. An anterior–posterior radiograph is obtained once the tube is passed to this predetermined length to determine that the tube is in the esophagus prior to further passage [13]. A radiograph must be obtained to document tube location prior to starting feeding.

 Percutaneous endoscopic gastrostomy (PEG)   

The development of the PEG procedure by Ponsky and Gauderer in the early 1980s was an important technological advance in the field of enteral access [22]. Over the ensuing twenty years or so, many commercial kits and variations in technique for PEG placement have been introduced.

Indications   

PEG tubes are indicated for those unable to consume sufficient nutrition over a period of greater than 30 days despite a functional gastrointestinal tract. Patients requiring PEG placement are often elderly, with comorbid diseases. Elderly patients referred for PEG placement had a 48% mortality at 7 days if they had prior aspiration, a urinary tract infection, and were older than 75 years. This was compared to a 4% mortality at 7 days if none of the aforementioned risk factors were present [23]. Stellato et al. reported that PEG placement can be safely performed in patients with prior abdominal surgeries [15]. PEG tubes are indicated for administration of hydration and medications as well as for gastric decompression. They are also placed for catabolic states such as burns, cystic fibrosis, and AIDS-related wasting syndrome.

Cancer patients   

One area of oncology in which PEG tubes are proven is in patients with head and neck cancer. The benefit of PEG tubes in this setting was illustrated in a retrospective study that had 40% (32/88) of patients receiving a PEG tube prior to chemotherapy and radiotherapy. Those who received a PEG lost an average of 3.1 kg compared to 7 kg of weight loss for those without a PEG. The same PEG group had significantly fewer hospitalizations for dehydration and malnutrition and had no interruption in treatment of their cancer [25].

Stroke   

Data also support the use of PEG tubes in those with dysphagia-associated central nervous system disorders. In one study, the authors reported a 1, 8, and 48 month survival of 78, 35, and 27%, respectively, when the most common indication was a hemispheric stroke [26].

Dementia   

Dementia is a frequent disorder of the elderly and indication for referral for PEG. Approximately 36 000 elderly patients with dementia receive a PEG each year [27]. However, the benefit of providing enteral nutrition in these patients is less clear [28]. No large randomized trials have demonstrated a difference in survival in demented patients with or without a PEG, although these trials are very difficult to construct ethically.

Contraindications   

Relative contraindications for PEG placement include the presence of gastric varices, obesity, prior gastric surgery, disease of the gastric or abdominal wall, ascites, and a coagulopathy. Absolute contraindications include the inability to transilluminate the anterior abdominal wall and an ineffective digital intrusion of the abdominal wall [29].

PEG technique   

Prophylactic antibiotics are given to reduce the risk of wound infections [30]. Any percutaneous enteral access procedure requires the combination of an adequate finger palpation on the anterior abdominal wall in combination with satisfactory endoscope transillumination. During instances where one of the above two requirements are unsatisfactory, a safe track maneuver may be performed to confirm that no loops of bowel are present between the anterior abdominal and gastric walls. In this situation, an 18 or 20 gauge can be passed through the same tract previously identified as gastric lumen with the anaesthesia needle. By applying back pressure with the syringe while withdrawing the needle, one will look for the appearance of stool or a sudden bolus of air within the syringe which would confirm passage through the colon [31].

The procedure is initiated with a lidocaine syringe advanced into the stomach while retracting the plunger. After air is noted in the syringe as the needle simultaneously punctures the gastric lumen, a small incision is made and a trocar is passed into the stomach along the same tract. A snare grasps the trocar as a guidewire is fed through it. The snare grasps the guidewire which is then pulled out of the mouth (Fig. 1). A PEG tube is either fastened to the guidewire and pulled into position (Ponsky) or is pushed over the guidewire (Sachs-Vine). Once the PEG tube is in proper position, the external bolster is pushed over the PEG towards the exterior abdominal wall [32].

The two most common methods, the Sachs–Vine (push) or Ponsky (pull) techniques, have been compared in a controlled trial. This trial did not show a significant difference in procedural-related success rate or overall outcome between the two techniques [32].

PEG tube management   

The external bolster is maintained 1–2 cm from the anterior abdominal wall. The wound should be cleaned twice daily with hydrogen peroxide, and a clean dressing should be applied over the external bolster. Caregivers must raise the head of the patient's bed 30–45 degrees during and for one hour after feeding.

Feeding   

An intermittent or continuous feeding regimen rather than the rapid bolus method may also be used to limit the risk of tube feed aspiration. Gastric residuals should be checked regularly and feeding intolerance should be monitored in all cases. Any gastric residual greater than 200 ml should be of concern [4].

Because of the hypotheses that a patient develops transient gastroparesis or the potential for intraabdominal PEG tube leakage after placement, there is no good consensus on when to feed a patient following PEG placement. Brown et al. randomized patients to begin feedings either 3 h or 24 h after PEG placement. Though there were no reported differences in tolerance or complications requiring discontinuation of tube feedings, wound infections were more common in the delayed feeding group [33].

Diarrhea   

Though universal recommendations are not available for preventing or eliminating diarrhea, it is possible to pay careful attention to fluid and electrolyte management in order to minimize any metabolic complications. In instances where an infectious source is suspected, the presence of fecal leucocytes is helpful. Obtaining a Clostridium difficile toxin, enteric stool pathogens, stool osmolality, and various medications should be ordered in the proper clinical context. An abdominal radiograph and a digital rectal exam will help rule out a stool obstruction with leakage of liquid stool [34].

Complications of PEG   

Most postprocedural complications arise from a patient's comorbidities, such as poor wound-healing, aspiration, or coagulopathy [35,36,37]. The most common complication is peristomal wound infection [35,38]. Excessive tightening of the bolster can cause tissue ischemia, wound leakage, and necrotizing fasciitis [39]. Peristomal wound infections are often treated for 7 days with an oral antibiotic such as cephalexin in order to cover skin-related microorganisms. The infected area should also have twice-daily topical cleansing with or without bactroban ointment. However, the tube needs to be removed in cases of worsening infection.

Major reported complications are rare and include haematoma, peritonitis, necrotizing fasciitis, gastric or colonic perforation, and gastrocolic or colocutaneous fistula [36–38,40]. In cases of colocutaneous fistula, the tube should be removed and the patient's condition should be monitored for appropriate closure of the fistulous tract. If the tract does not heal, however, surgery is warranted to repair the fistula.

Minor reported complications include peristomal leakage, pneumoperitoneum, fever, ileus, volvulus, cutaneous or gastric ulceration, and tube extrusion or migration [36,38,40–42].

Tube dislodgement   

In cases of tube extrusion within 4 weeks of tube placement, fluoroscopy can be used to replace the tube at the bedside or endoscopy may be repeated. If the tube is extruded after 4 weeks of placement, the tract may be mature enough to replace the tube at the bedside as long as gastric juices are aspirated. It should also be noted that tubes are not routinely replaced except in circumstances where the tube becomes dysfunctional or degraded.

 Percutaneous endoscopy gastrostomy/jejunostomy (PEG/J)   

Percutaneous endoscopic gastrostomy/jejunostomy (PEG/J) uses a two-tube system in which a jejunal feeding tube is passed through a gastrostomy tube to allow concurrent jejunal feeding and gastric decompression. Early designs of PEG/J systems were crude, which made the placement of the J-tubes difficult. An over-the-guidewire technique has been recently employed to overcome this difficulty [43].

Indications/contraindications   

A PEG/J is performed for patients who are eligible for a PEG tube (Fig. 1), but who cannot tolerate the gastric feedings and/or are at a risk for aspiration. Typical patients in which a PEG/J should be performed are those with aspiration, gastroparesis, severe GERD, prior gastric surgery, and with gastric outlet obstruction.

J tube placement through a PEG (PEG/J)   

Original PEG/J placement techniques relied on dragging the J-tube through the G-tube into the small bowel via an attached suture (Fig. 2). This technique resulted in poor initial outcomes as there were multiple difficulties including pulling the J-tube out of position with removal of the endoscope [44–46]. Recent techniques have emphasized placement of a guidewire through the PEG tube with subsequent passing of the jejunal tube over the guidewire. DeLegge et al. reported placing a guidewire into the proximal jejunum using a standard upper endoscope and grasping forceps [43]. After the guidewire is placed in the proximal jejunum by the grasping forceps (Fig. 3), the J-tube is passed over the guidewire. The endoscope is subsequently withdrawn to the stomach using the 'exchange technique' to maintain the J-tube in the jejunum (Fig. 4). Insufflation of the stomach is maintained by use of an air plug in the distal end of the PEG [47].

Adler et al. described a separate technique for placing a jejunal tube through a PEG that uses endoscopy of the existing PEG with a neonatal endoscope or bronchoscope placed into the jejunum. A guidewire is placed through the biopsy channel into the jejunum and the endoscope is removed. The J-tube is then placed blindly or with fluoroscopic guidance [48].

PEG/J tube management   

The management of PEG/J tubes is similar to that of PEG tubes. J-tubes need to be flushed aggressively so as to avoid clogging. Clogging rates of J-tubes have ranged from 3.5 to 35% [49,50]. Semi-dissolved medications, bulking medications such as Metamucil, and checking residuals all lead to an increased incidence for tube occlusion [51]. Medication administration may be through the gastrostomy tube, which may also be used for decompression in those with gastroparesis or gastric outlet obstruction.

Complications of PEG/J tubes   

Complications of PEG/J tubes include those for a PEG and a nasojejunal tube, in addition to retrograde migration of the J-tube and its dysfunction owing to kinking or clogging. The average longevity of the J-tube within the PEG/J system is 3–6 months [47,52].

 Direct percutaneous endoscopic jejunostomy (DPEJ)   

Indications/contraindications   

The indications and contraindications for a DPEJ are similar to those for a PEG/J with the exception of the lack of need for gastric decompression. As with a PEG/J, infusion of tube feedings distal to the ligament of Treitz may be indicated while resting pancreatic exocrine function after acute pancreatitis, symptomatic pseudocysts, and pancreatic ductal disruptions.

DPEJ technique   

Obtaining jejunal access with direct percutaneous puncture of the jejunum under endoscopic guidance requires the use of an enteroscope or pediatric colonoscope to obtain proper position. Glucagon may be given to decrease small bowel motility during puncture to avoid losing small bowel access [53,54]. A standard PEG-type procedure is performed after transillumination of the jejunum. A 21-gauge 1.5 inch long anesthesia needle is used for the initial puncture of the jejunum. A purposeful stabbing motion should be used so as to avoid the bowel wall being pushed away from the needle. Maintaining this needle in place by grasping it with a snare stabilizes the jejunum (Fig. 5) and allows insertion of the larger trocar assembly alongside of the indwelling anaesthesia needle (Fig. 6). A guidewire is inserted through the trocar assembly and the remainder of the procedure is performed as a standard pull PEG would be performed (Fig. 7) [7,53,54].

Mellert et al. reported successful DPEJ tube placement in 39 of 44 patients, with local complications requiring only conservative management in 5 patients [53]. Shike et al. reported success in 39 of 42 patients with three local skin infections reported that responded to antibiotics [54].

DPEJ tube management   

Immediately after DPEJ placement, it may be helpful to leave the tube unclamped so as to decompress the small bowel from the substantial amount of air that is insufflated during the procedure. Otherwise, the management is similar to that of PEGJ tubes.

DPEJ tube complications   

Complications and technical failures have been presented in 3 retrospective series on DPEJ outcomes. Technical failure rates ranged from 12 to 28%. Complications included bleeding, abdominal wall abscesses, colonic perforations, peristomal infections, enteric ulcers, and enteric leakage. Tube-related malfunctions similar to PEG tubes also occurred [53,55,56].

 Enteral formulations   

Many formulations for enteral feeding are available; they include blenderized, lactose-containing, lactose-free, elemental, specialty, modular, and supplemental regimes.

Blenderized formulations   

Blenderized formulations are combinations of vitamins and minerals added to table foods. Because of this, they have more fiber and high viscosity and osmolarity. They require a functional gastrointestinal tract but are not recommended for jejunal feeding or in small-caliber tubes because of their propensity for clogging.

Lactose-containing formulations   

Lactose-containing formulations are rarely used today.

Lactose-free formulations   

Lactose-free formulations are the basic feeding formulations and are designed for long-term use. Standard formulations have 15–20% calories from proteins, 45–60% calories from carbohydrates, and 30–40% calories from fats. Generally, these formulations provide 1 kcal/ml, although they may be concentrated to 1.5–2 kcal/ml.

Elemental formulations   

Elemental formulations are designed for patients with limited digestive capacity. They are delivered as free amino acids, dipeptides, or tripeptides. They are highly osmotic because of the presence of multiple small-size particles.

Specialty formulations   

Specialty formulations are designed for patients with special nutritional requirements based on specific disease processes. Various specialty formulations have been devised for those with renal failure, hepatic failure, those severely stressed or traumatized, and pulmonary patients. There are no data to show that these specialty formulations improve survival for their intended disease state.

Modular feedings   

Modular feedings consist of individual nutritional components that are mixed to create a custom enteral formulation. They exist as carbohydrates, proteins, or fats.

Supplemental regimes   

Specific supplements are taken with or between meals for those who cannot meet all of their caloric needs otherwise [57].

Immune enhancing diets (IED)   

Immune enhancing diets (IED) may be useful for patients who are undergoing elective:

• Gastrointestinal surgery

• Blunt and penetrating torso trauma

• Anticipated prolonged need for a mechanical ventilator

• Major head and neck surgery

• Major burns

If possible, administration of an IED should be initiated 5 to 7 days prior to elective surgery. In these cases, feedings should be advanced as tolerated until 1500 ml is administered daily or greater than 50–60% of calculated nutrient goals are met. Current evidence suggests a reduction in later infectious complications and reduced hospital stay, antibiotic needs, ventilator days, and reduced multiple organ dysfunction [58].

 Conclusions   

Enteral access is the foundation of enteral nutritional therapy. The patient's specific disease state, comorbidities, medical therapy, life expectancy, and expected time of need will determine the type of enteral access device [1]. Enteral feeding, as opposed to parenteral nutrition, improves epithelial structure and function, enhances mucosal immunity, and provides rapid advancement of feeds. Considering the available data and our clinical experience, enteral nutrition should be used instead of parenteral nutrition whenever possible as it is proven to be more cost-effective and likely safer [4]. Percutaneous enteral access has become the standard of care for long-term feeding assistance. Intragastric feeds are generally preferable due to a more physiologic nature, but tube feedings administered in the jejunum should be used in patients at risk for aspiration [34,59].

The placement of a PEG, PEG/J, and DPEJ are important tools for the provision of nutritional support. Exciting new techniques have provided the gastroenterologist with time efficient and less invasive tools to ensure proper nutritional management [1]. Recently, there have been technological advances for approaching small bowel access. Over-the-guidewire techniques are effective for placing a J-tube via a PEG [47]. More recently, PEG/J has been associated with limited complications and can remain functional for a longer period of time. Most recently, DPEJ has been shown to be safe and effective. It is imperative that the endoscopist, along with nutritional support teams, becomes familiar with all of these techniques, which can be a valuable adjunct to improve care and decrease enteral-related complications [5]

However, relatively small, retrospective, uncontrolled trials focusing on differing patient populations have limited the development of evidence-based guidelines. When achieved, these guidelines need to incorporate reasonable goals and objectives. Weight gain, survival, or improvement in functional status may be unrealistic goals for certain patient populations. Maintaining or improving a patient's health-related quality of life, reducing pain and suffering, and providing access for hydration and medications may be more reasonable and obtainable goals, even in patients with ultimately terminal diseases [26,60,61].

 Outstanding issues and future trends   

The field of nutrition support is fast becoming part of the accepted practice of many gastroenterologists and surgeons. Developments will be led by those physicians with a special interest in enteral access and nutrition, but all digestive clinicians will need to develop a basic understanding of nutrition support and nutrition intervention. Endoscopists should become more familiar with nutrition therapy, such that we are not regarded simply as only the technologists who put in feeding tubes, but as physicians who provide the continuum of care from nutrition assessment, through tube placement, nutritional therapy plan development, and complication management. Training programs will need to be enhanced to provide a level of intensity of specialist training approximating that of luminal gastroenterology, hepatology, and pancreaticobiliary medicine.

There a relatively few outcomes studies of enteral access techniques, compared to other therapeutic endoscopy procedures. The emphasis on enteral access training and research support by our endoscopy organizations, such as the American Society for Gastrointestinal Endoscopy, will encourage both young and seasoned investigators to evaluate the utility of enteral access and nutritional support. This will be important in disease states such as pancreatitis, gastrointestinal motility disorders, cancer, and dementia.

Enteral access technology, both from the endoscopist's standpoint and the patient's standpoint, will continue to evolve. Device development will allow us to place enteral access devices that are efficient, but not obtrusive to the patients who receive them. These same access devices will serve as drug delivery systems, as drugs are combined with tube feedings, allowing an efficient mechanism for both feeding patients and treating their medical diseases in a concurrent fashion.

Small bowel access will continue to evolve. Access devices will be developed that not only provide routes for enteral nutrition, but also serve as access ports for the endoscopic treatment of other gastrointestinal diseases. Material developments should make these devices more compatible with human tissue, thus allowing access ports to become part of the abdominal wall, rather than a separate tube.

The future of nutrition and enteral access is occurring now. Continued growth and development will be assured as the need for this therapy increases, especially among our ageing population.

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