Enteric Feedings

Indications

Indications for Enteral Feeding

Enteral tube feeding is indicated in patients who cannot maintain adequate oral intake of food or nutrition to meet their metabolic demands. Healthcare professionals commonly use enteral feeding in patients with dysphagia. Patients with dysphagia sometimes cannot meet their daily nutritional needs, even with modification of food texture or consistency.

For enteral feeding to be successful, the GI tract should be accessible and functional. Inaccessible GI tracts, malabsorption, and severe GI losses might challenge enteral feeding. The alternative is parenteral feeding.

Indications

• Comatose patients on mechanical ventilation or with a severe head injury
• A neuromuscular disorder affecting swallowing reflex: Parkinson's disease, multiple sclerosis, cerebrovascular accident.
• Severe anorexia from chemotherapy, HIV, sepsis
• Upper GI obstruction esophageal stricture or tumor
• Conditions associated with increased metabolic and nutritional demands include sepsis, cystic fibrosis, and burns [2]
• Mental illness like dementia [3][4][5][6][7][8]

Enteral Nutrition in Critical Illness

There is overwhelming evidence that enteral feeding is the best approach for nutrition in critically ill patients. The GRADE system working group came up with the following recommendation.

• Enteral nutrition has been associated with an improvement in nutrition variables, a reduction in the length of hospital stay, and a lower incidence of infection.
• Critically ill patients who cannot tolerate oral feeding for greater than 72 hours should receive specialized nutritional support.
• Enteral nutrition is the preferred mode of feeding when compared to parenteral nutrition.
• Enteral nutrition should be started within 48 hours of admission.
• It should provide between 25 to 30 kcal/kg per day.
• The goal caloric intake should be achieved within 48 to 72 hours.
• Enteral nutrition should be deferred until the patient is stable hemodynamically.
• The presence of flatus, stool passage, or bowel sounds should not be a prerequisite for starting enteral nutrition.[8]

Caloric Consideration

Resting energy expenditure can be calculated using indirect calorimetry. This method calculates the caloric requirements in patients requiring enteral feeding. When indirect calorimetry is unavailable, approximately 25 kcal/kg per day is the approximate energy requirement. Clinicians can calculate caloric intake for patients on mechanical ventilation using the Penn State equation.[9]

Carbohydrate intake should be approximately 4 gm/kg daily with a target glucose level below 180 mg/dl. Lipid intake should be between 0.7 to 1.5 gm/kg per day. Amino acid should be adjusted to 1 to 1.8 g/kg per day with an adequate supply of micronutrients.[10]

It is highly recommended that enteral feeding be started as early as possible in critically ill patients.[10][11][12]

Hypocaloric enteral intake is beneficial at the initial stage of critical illness as it can help prevent hyperglycemia, which is linked to a higher risk of mortality. Some authorities recommend around 80% of nutritional needs in the first 7 to 8 days of illness, which can gradually increase during recovery.

Contraindications

Absolute Contraindications

• Hemodynamic instability with poor end-organ perfusion. Enteral feeding in patients with bowel ischemia or necrosis can make a bad situation worse
• Active GI bleeding
• Small or large bowel obstruction
• Paralytic ileus secondary to electrolyte abnormalities, peritonitis

 Relative Contraindications

• Moderate to severe malabsorption
• Diverticular disease
• Fistula in the small bowel
• Short bowel disease in the early stages.

Special Cases

Acute Kidney Injury

In acute kidney injury (AKI), nutritional support conserves lean body mass and energy reserve and prevents malnutrition.

Patients with AKI and renal failure might be in a non-hypercatabolic or hypercatabolic state with excessive sodium, potassium, and phosphate load. In a non-hypercatabolic state, high-energy enteral nutrition with normal protein content and low sodium, potassium, and phosphate load are recommended.[13][14] In AKI with a hypercatabolic phase, a low protein (2 to 2.5g/kg per day) and low electrolyte enteral nutrition are recommended. Besides monitoring electrolytes like sodium, potassium, phosphorus, and calcium, clinicians should pay special attention to micronutrients like zinc, selenium, thiamin, folic acid, and vitamins A, C, and D.

Acute Liver Failure and Liver Transplantation

Liver failure is associated with the loss of the synthetic function of the liver. Liver failure patients also have an impaired ability to synthesize clotting factors. Enteral feeding should be cautiously approached in patients with liver failure because of the inherent risk of gastrointestinal bleeding from varices and coagulopathy. In acute liver failure, parenteral nutrition might be better if the gut is not viable or if the risk of hepatic encephalopathy is high. A balanced energy supply from carbohydrates and protein is recommended if enteral feeding is used. Caloric intake should be around 25 kcal/kg per day. Enteral feeds should contain adequate potassium, magnesium, and zinc. In liver transplant patients, early enteral feeding via a transpyloric approach is recommended.[15]

Acute Lung Injury (ALI), Acute Respiratory Distress Syndrome (ARDS)

This is 1 of the most common reasons for admission into the intensive care unit (ICU). Daily protein intake should be around 1 to 1.8 g/kg daily. The use of high-fat and low carbohydrate is not indicated. ALI and ARDS require an enteral diet rich in omega-3 fatty acids and antioxidants.[16]

Multiple Trauma

A patient who sustained multiple trauma should be started early enteral feeding. We recommend that trauma patients be started on a total caloric intake of about 25 to 30 kcal/kg daily. We also recommend arginine and omega in patients with multiple traumas.[17][18][19]

Abdominal Surgery

The nutritional needs of patients with abdominal surgery are similar to those of other critically ill patients. Surgery causes both inflammatory and metabolic changes in the body. A post-surgical patient with malnutrition might have delayed wound healing and dehiscence and decreased immunological functions, placing the patient at risk for infectious and cardiopulmonary complications. This can prolong hospital stays and cause a higher rate of mortality.[20]

Acute Pancreatitis

Inflammation of the pancreas can provoke a systemic inflammatory response syndrome. This causes a hypermetabolic, hyperdynamic, and catabolic state. Classically, acute pancreatitis is treated with bowel rest and parenteral nutrition. It has been shown that this approach is associated with high morbidity and mortality. In acute pancreatitis, there is intestinal barrier dysfunction, which is associated with multiple organ failure, pancreatic necrosis, and mortality. Based on these facts, the current recommendation is to start early enteral feeding via the jejunum within 48 hours of hospitalization.[21][22]

Equipment

Types of Enteral Feeding Tubes

There are several types of enteral feeding tubes. They are usually made of polyurethane or silicone. Feeding tube diameters are measured in French units (Fr). Each French unit is equivalent to 0.33 millimeters. Feeding tubes are usually denoted or classified by the site of placement.

• Nasogastric tube
• Nasoduodenal tube
• Nasojejunal tube
• Gastrostomy tube
• Jejunostomy tube
• Gastrojejunal tube

Tubes can be placed:

• Manually
• Endoscopically 
• Surgically
• By interventional radiology[23]

Nasogastric Tube

A nasogastric tube (NG) is mainly utilized for patients with no issues with vomiting, gastroesophageal reflux (GER), poor gastric emptying, and no evidence of ileus or small or large bowel obstruction. NG tube is risky in patients with poor swallowing coordination or reflex. Fine bore 5 to 8 Fr NG is usually recommended. If there is a need for nasogastric decompression, a larger bore NG can be used. For patient safety, the recommendation is that well-trained and qualified medical personnel place the feeding tube. After the placement, the position should be verified by auscultation or x-ray. Although not routinely recommended, an x-ray confirms NG tube placement for high-risk patient populations, specifically intensive care and neonatal patients. The National Patient Safety Agency advocates analyzing gastric aspirate with pH-graded paper to confirm the proper position. The pH should be less than 5.5 before feeding is started.

Nasoduodenal and Nasojejunal Tube

These are enteral feeding tubes with a tip in the duodenum or jejunum. They can be placed at the bedside or with fluoroscopy guidance.

Gastrostomy Tube

The feeding tube passes through the anterior abdominal wall into the gastric cavity. A gastrostomy tube is utilized for patients who require long-term feeding. It can be placed via endoscopy percutaneous endoscopic gastrostomy (PEG).[24][25] PEG tubes are for patients who require long-term nutritional support. PEG tube with jejunal extension is associated with tube dislocation and dysfunction.[25] A gastrostomy feeding tube can also be placed radiologically, surgically, or via endoscopy.[26]

Jejunostomy Tube

This feeding tube passes through the anterior abdominal wall into the jejunum. It can be placed surgically or radiologically by extending through the pylorus into the jejunum. Endoscopically, a percutaneous endoscopic gastrojejunostomy (PEGJ) can be performed. Direct percutaneous endoscopic jejunostomy tube placement is less commonly performed, but PEGJs are more robust and less likely to be dislocated.[25]

Personnel

Nutritional Support Team

Using the current protocol and guidelines, an interprofessional approach is the best way to manage patients who require enteral feeding. A nutrition support team comprises the physician, nurse, clinical pharmacist, and nutritionist.[27] Provision of optimal enteral nutrition can be achieved by:

• Identification of patients at risk for malnutrition
• Performance of a comprehensive assessment of the patient's nutritional status
• Provision of a safe, adequate, and effective nutritional support

 Services that the nutrition support team can offer include:

• Consultation service for nutritional support
• Development of nutrition protocol for both medical and nursing staff
• Research and quality improvement projects in nutrition
• Staff education and development

Technique or Treatment

Delivery Techniques

There are several modalities of delivering enteral feeds. Traditionally, enteral feeding should be started about 12 to 24 hours after the placement of PEG. This allows for a better seal to develop at the site of insertion of the PEG tube.[27][28] More recent studies have shown that enteral feeding can be initiated from 3 to 4 hours after the insertion of the PEG.

Bolus Intermittent Feeding with a Bulb or Syringe

Enteral feeding delivers about 100 to 400 ml over 5 to 10 minutes. It is mostly used in ambulatory settings, and the risk of aspiration is high.

Cyclic Intermittent Feeding

This method is used for patients in a semi-recumbent position. Enteral feeding is delivered via a pump or gravity and lasts 8- 16 hours.

Intermittent Drip

This is popular for home enteral feeding. Approximately 1.5 to 2 liters of feeding can be delivered overnight over an 8 to 16-hour period. Feeding is delivered via gravity or pump.

Constant Infusion

This method is used for bedridden patients. Feeding is usually delivered via gravity or pump. The head is inclined at 45% to reduce aspiration or regurgitation.

There are 4 techniques for jejunostomy placement: open surgical technique (longitudinal or transverse Witzel), laparoscopic technique, needle catheter technique, and percutaneous technique. Although the preferred technique depends on the type of patient and the surgeon's expertise, minimally invasive techniques are the standard of care.

Open Surgical Technique

The patient is prepped and draped with sterility. An exit site is chosen in the LUQ, preferably a few centimeters away from the midline. A stab incision is made and dissected with tonsil forceps. A loop of proximal jejunum is delivered into the wound. A diamond-shaped purse-string suture is tied to the antimesenteric border of the jejunal loop, and a small incision is given in the center of the suture, large enough to accommodate the jejunostomy tube. The tube is inserted into the jejunum with care to ensure enough tube length to prevent the backflow of tube feeds. The purse-string suture is secured tightly without kinking the tube.

The Witzel technique is used to prevent extravasation of enteric contents at the exit site of the jejunostomy tube. This involves placing the tube along the length of the bowel for about 5 cm proximally and creating a serosal tunnel to imbricate the tube into position. The serosal tunnel is created by taking perpendicular Lambert sutures with 3-0 silk on either side of the tube. Once the tube is delivered through the abdominal wall, the jejunal loop with seromuscular sutures is attached to the abdominal wall. This is done to prevent bowel obstruction or volvulus.[10]

Laparoscopic Technique 

It is a minimally invasive approach and is the preferred modality with the current advancement of technology. The patient is placed in a supine position initially. After creating the pneumoperitoneum and visual entry into the abdomen, the ligament of Treitz is visualized by upward retraction of the bowel and removal of the omentum. The patient is kept in a reverse Trendelenburg position to allow the bowel to be traced. The jejunum is traced from the ligament of Treitz for 1-2 ft, and a site is chosen, which may be adhered to the abdominal wall. Four seromuscular sutures in the shape of a diamond are placed on the antimesenteric border of the jejunum. The loose ends of the sutures are used to pull the jejunum to the corresponding site over the abdominal wall. A percutaneous needle enters the jejunum, and a guidewire is passed into the jejunum. The opposite side of the abdominal wall is inspected to ensure the guidewire has not passed through. Using serial dilators, the skin, and subcutaneous tissue are dilated to make a track for the passage of the jejunostomy tube with a stent. Once the tube is in position, the stent is removed, and the balloon is inflated. The tube is secured, and laparoscopic incisions are closed with sutures and glue.[11][12]

Needle Catheter Technique

This technique is often used as part of laparotomy with major gastrointestinal resection. A submucosal tunnel is created through the anti-mesenteric well of the jejunum with a needle catheter after its introduction into the abdominal cavity. The tunnel should be about 4-5 cm. This prevents the development of a fistula after the placement of the tube. The catheter is introduced through the needle and sutured to the jejunal wall with a purse-string suture. Finally, the jejunum is attached to the peritoneal lining with sutures. Tube feeds can be started soon after surgery, within 6-12 hours.

Percutaneous Technique (Direct Percutaneous Endoscopic Jejunostomy) 

Percutaneous insertion is done with the help of endoscopy. An enteroscope or colonoscope is passed into the jejunum. Transillumination of the tip of the scope is used to identify the position of the endoscope over the abdominal wall. A trocar is inserted through the abdominal wall into the jejunum, and a guidewire is passed distally into the jejunum. The tips of an awaiting snare or forceps are used to grasp the wire. A dilator is subsequently passed to create the track for the tube, and the tube is secured similarly to a 'pull-PEG' technique.[13][14]

Complications

Tube-Related

Mechanical Complication

Tube placement for enteral feeding might cause mechanical complications. Some mechanical complications from tube feeding are listed below.

• Tube malposition
• Tube obstruction
• Accidental dislodgment of tube
• Breakage of the feeding tube
• Leakage of the feeding tube
• Erosion and ulceration near the site of insertion
• Intestinal obstruction
• Bleeding

Tube for enteral feeding can be inserted nasally through the guided percutaneous application or surgical technique.

Nasoenteral insertion is mostly done blindly by the bedside, with about 0.5% to 16% mispositioning in the pleura, trachea, or bronchial trees. This can cause the infusion of enteral feeds in the tracheobronchial tree, causing a pulmonary abscess or pneumothorax.[29] Installing air or auscultation is not an accurate method for determining proper tube placement. The best confirmation is with radiography.[30][30] The failure of bedside nasoenteral tube placement indicates fluoroscopy or endoscopy-guided tube insertion.

Infectious Complications

• Infection at the site of tube insertion
• Aspiration pneumonia
• Ear and nasopharyngeal infection
• Infective gastroenteritis with diarrhea
• Peritonitis

Tube placement in enteral feeding is sometimes associated with the abovementioned infectious processes. Aspiration pneumonia is reported in 89% of patients on enteral feeding with no clear benefit of gastroenteric feeding over nasogastric. Distal duodenal or jejunal feeding might prevent the regurgitation of enteral feeds.[30]

Complications from the enteral feeding tube also depend on the following:

1. The size of the tube
2. The tube material
3. The diameter of the tube

Spark et al. critically reviewed pulmonary complications from gastroenteric tube placement. In 9931 cases of tube placement, there was 1.9% (187) malposition in the tracheobronchial tree. The 187 misplaced tubes resulted in 35 pneumothoraxes (18.7%) with at least 5 mortalities.[31]

Gastrointestinal Complications

Enteral feeding is associated with several GI complications

• Nausea and vomiting
• Diarrhea
• Constipation
• Cramps and bloating
• Regurgitation and aspiration 

Nausea

Nausea and vomiting are common after the initiation of enteral feeding, about 20% to 30%. Non-occlusive bowel necrosis and aspiration can also occur. This is associated with high mortality.[32][33]

Diarrhea

This is the most gastrointestinal complication seen in enteral feeding. Diarrhea occurs in about 30% of patients admitted to the medical or surgical wards and about 80% of patients in the ICU.[28][34][35]

Diarrhea in enteral feeding is a result of many factors. Using antibiotics and other medications in enteral feeding is a common cause of diarrhea—medications like antacids, oral magnesium or phosphate, antacids, and prokinetic agents. Oral and intravenous antibiotics can also favor the growth of Clostridium difficile, Escherichia coli, and Klebsiella. The sorbitol-containing solution can also trigger profuse diarrhea in patients on enteral feeding. Using fiber based on the meta-analysis result can significantly reduce the incidence of enteral feeding-associated diarrhea, especially in high-risk, post-surgically, and critically ill patients.

Constipation

This is a less common complication associated with enteral feeding. Constipation is more common in patients on long-term enteral feeds. Some studies suggest that fiber supplementation might help reduce the percentage of patients reporting constipation in enteral feeding.

Aspiration Pneumonia

This is a potentially life-threatening complication from enteral feeding. It occurs because of the aspiration of oral secretion or gastric secretions with enteric secretions. Aspiration is more common when patients are fed via a nasogastric tube in a supine position.[36][37] The cause of aspiration pneumonia in enteral feeding is multifactorial.

• Gravitational backflow
• Lower esophageal sphincter impairment
• Infrequent contract of the esophagus
• The presence of a tube near the gastric cardia
• Impaired level of consciousness
• Poor gag and cough reflexes are seen in neurologically impaired patients with stroke or dementia [38]

To prevent aspiration, place the enteral feeding tube about 40 cm distal to the ligament of Treitz. This applies to patients with a higher risk of aspiration.[39][40]

Metabolic Complications

Enteral feeding is associated with metabolic complications. A common complication seen in malnourished patients is refeeding syndrome. This phenomenon was first described in Far East prisoners during the Second World War.[41][42][43]

Patients with anorexia nervosa, hyperemesis, alcoholism, and malabsorption syndrome like short bowel syndrome who are started on enteral feeding are prone to refeeding syndrome.

The pathophysiology of the refeeding syndrome is still poorly understood. In starvation, the cellular membrane system downregulates with the loss of intracellular potassium, phosphorus, magnesium, and calcium. The total body content of these ions is depleted. The cell's intake of sodium and water is also increased. The sudden reversal of malnutrition with enteral feeding is due to the cell's uptake of potassium, phosphorus, magnesium, and calcium back with the simultaneous movement of water and sodium out of the cells. The undernourished kidney is also impaired and cannot handle the sodium and water load.

Hypophosphataemia is the hallmark of refeeding syndrome. Hypophosphatemia can cause rhabdomyolysis, cardiac failure, arrhythmia, muscular weakness, leukocyte dysfunction, seizure, coma, and sudden death.[44]

The phenomenon is more common in enteral than parenteral feeding.[45]

Awareness of the syndrome is the key to treatment and prevention.

Patients at Risk for Re-feeding Syndrome

• Chronic alcoholism
• Anorexia nervosa
• Postoperative patients
• Elderly patients
• Prolonged fasting
• Morbid obesity associated with profound weight loss
• Malabsorption syndrome: Cystic fibrosis, inflammatory bowel disease, and short bowel syndrome[46]

To manage refeeding syndrome, the patient's cardiovascular status should be monitored closely, preferably in the ICU. Judicious monitoring of electrolytes and micronutrients should also be implemented.

Goal caloric intake should target about 50% to 75% of daily requirements.

Body Weight

• Less than 7 years: 80 to 100kcal/kg body weight per day
• Seven to 10 years: 80 to 100kcal/kg body weight per day
• Eleven to 14 years: 60 kcal/kg body weight per day
• Fifteen to 18 years: 50kcal/kg body weight per day
• Older than 18 years: 25 kcal/kg body weight per day, an average of 1000 kcal per day initially
• Thiamine, riboflavin, folic acid, and pyridoxine should be supplemented, including fat-soluble vitamins A, D, E, and K.

Minerals

• Sodium should be restricted, I mmol/kg of body weight per day or 1.5 g per day, but an adequate amount of phosphorus, magnesium, and potassium should be given.
• Magnesium (0.8 to 1.6mmol/L)
• For hypomagnesemia, start at 0.5 mmol/kg per day over 24 hours, then 0.25 mmol/kg of body weight per day for 5 days
• Maintenance 0.2 mmol/kg per day intravenous or 0.5 mmol/kg per day oral
• Hypophosphatemia
• A normal range is 0.85 per 1.40mmol/L
• For mild hypophosphatemia (0.6 to 0.85 mmol/L), start at 0.3 to 0.6 mmol/kg of body weight per day
• For moderate hypophosphatemia (0.3 to 0.6 mmol/L), start at 0.3 to 0.6 mmol/kg of body weight per day
• In less than 0.3 mmol/L of severe hypophosphatemia, give IV sodium or potassium phosphate 0.8 mmol/kg of body weight in half normal saline over 12 to 24 hours.[47][48]

Complications Associated with PEG Placement

Peristomal Wound Infection

Wound infection occurs after PEG placement with an incidence of about 3 to 70%. The technique of placement, obesity, malnutrition, steroid, or immunosuppressive therapy can cause wound site infection. Prophylactic antimicrobial therapy has been shown to reduce the incidence of wound infection after placement of PEG. First-generation cephalosporins or penicillin give adequate coverage.[49][50][51]

Clogged Feeding Tube

The clogging of feeding tubes can be as high as 25%. Clogging occurs when very thick feeds and medications are delivered through a relatively thin tube. Repeated gastric aspiration is discouraged since the low pH of gastric fluid can promote protein coagulation.[52] After delivering thick feeds or medications, the feeding tube should be flushed with about 40 to 50 mL of water. A clogged feeding tube can also be cleared mechanically using various endoscopic catheters, braided quid wires, or plastic brushes.

Peristomal Leakage

This is also a complication of PEG tube placement for enteral feeding. Several factors can contribute to leakage. Excessive pulling, tugging, and increased gastric secretion inhibit wound healing, like malnutrition, diabetes, and immunodeficiency. This can be prevented using antisecretory agents like proton pump inhibitors (PPI). Skin protectants and barrier creams can also be used.

Bleeding

The incidence of bleeding is about 2.5% after placement of PEG.[53][54] This might be secondary to mucosal tears or damage to a local vessel. Risk factor for bleeding includes the use of antiplatelet or anticoagulation therapy. Based on the current recommendations, aspirin can be continued in high-risk patients. Warfarin is recommended to be discontinued, and unfractionated heparin can be used as a bridge.[54]

Colonic Fistulae

Misplacement of PEG for enteral feeding might lead to the formation of gastrocolic, colocutaneous, and gastro colocutaneous fistulae. A gastrocolic fistula connects the wall of the stomach and the colon. Gastro colocutaneous fistula is an epithelial connection between the wall of the stomach, colon, and skin that can occur because of iatrogenic puncture or direct erosion of the PEG into the colon wall and the skin.[55][32][56][57][58]

The gastroscope should be transilluminated through the anterior abdominal wall to prevent colonic misplacement. The endoscopically visible imprint of a finger or needle is considered a “condition sine qua non” before introducing the needle through the stomach.[59] Clinically, a fistula is associated with watery diarrhea around the site of the PEG or stool around the site of insertion of the PEG. In rare instances, fistulae formation can cause peritonitis, infection, or fasciitis. Injection of contrast into the PEG can establish the diagnosis. Management can be conservative with removing PEG and awaiting the spontaneous fistulae closure. For more severe cases, endoscopic intervention or invasive laparotomy with colonic exploration might be necessary.

Pneumoperitoneum

This can occur in 8% to 18% of PEG tube placements.[60][61][62][27] This is a relatively benign condition that does not warrant any intervention.

Clinical Significance

Clinical significance cannot be overemphasized. Utilizing the gut to provide nutrients helps maintain gut integrity, stimulation, and modulation of the immunological properties of the GI tract.[63]

Enhancing Healthcare Team Outcomes

Improving the outcome of enteral feeding requires an interprofessional approach. Enteral feeding involves coordination among the nutritional support team. The nutrition support team is made up of the following:

• Clinician
• Nutrition nurse specialist
• Dietician
• Pharmacist

The clinician coordinates and directs the care related to enteral feeding. The clinician determines the optimal feeding regimen for the patient. A nutrition nurse specialist is primarily responsible for educating the patient on using the feeding tube. The nurse also supervises the tube care and notifies the clinician if any complications develop. The dietician manages the evaluation of the nutritional requirements, including the calculation of the daily caloric need and the optimal fluid requirements. The pharmacist provides the enteral feed and can mix and compound parenteral nutrition. The pharmacist advises on the compatibility of nutrients and interaction. Other ancillary staff include the social worker, physical, occupational, and speech therapists, as well as a case manager, who helps arrange home supplies.[64] Care coordination, open communication, and accurate patient record-keeping are all aspects of the interprofessional care model that drive optimal patient outcomes.