Medical Nutrition Therapy
Enteral nutrition is administration of a specialized liquid food mixture that contains proteins, carbohydrates, lipids, vitamins, and minerals into the stomach or small bowel through tube-feeding. Although enteral nutrition may be administered orally, enteral nutrition in hospitalized patients generally refers to products administered through a nasoenteric tube that delivers the enteral nutrition product directly to the stomach, duodenum or jejunum. Alternatively, enteral nutrition may be delivered via a surgically implanted tube, such as a gastrostomy tube or a jejunostomy tube, with the rate of administration controlled using an infusion pump, gravity drip system, or as boluses via a syringe. For short-term enteral nutrition, a nasogastric or orogastric tube may be used to administer formula. However, long-term enteral nutrition is generally administered through a surgically placed gastrostomy or jejunostomy tube.
What is a Feeding tube?
A feeding tube is a medical device used to provide nutrition to people who cannot obtain nutrition by mouth, are unable to swallow safely, or need nutritional supplementation. The state of being fed by a feeding tube is called gavage, enteral feeding or tube feeding. Placement may be temporary for the treatment of acute conditions or lifelong in the case of chronic disabilities. A variety of feeding tubes are used in medical practice. They are usually made of polyurethane or silicone. They are classified by the site of insertion and intended use.
Medical Causes for the of Tube feeding
There are dozens of conditions that may require tube feeding. The more common conditions that necessitate feeding tubes include prematurity, failure to thrive (or malnutrition), neurologic and neuromuscular disorders, inability to swallow, anatomical and post-surgical malformations of the mouth and esophagus, cancer, Sanfilippo syndrome, and digestive disorders.
People with advanced dementia who get feeding assistance rather than feeding tubes have better outcomes. Feeding tubes do not increase life expectancy for such people, or protect them from aspiration pneumonia. Feeding tubes can also increase the risk of pressure ulcers, require pharmacological or physical restraints, and lead to distress. In the final stages of dementia, assisted feeding may still be preferred over a feeding tube to bring benefits of palliative care and human interaction even when nutritional goals are not being met.
Feeding tubes are often used in the intensive care unit (ICU) to provide nutrition to people who are critically ill while their medical conditions are addressed; as of 2016 there was no consensus as to whether nasogastric or gastric tubes led to better outcomes.
Mechanical obstruction and dysmotility
There is at least moderate evidence for feeding tubes improving outcomes for chronic malnutrition in people with cancers of the head and neck that obstruct the esophagus and would limit oral intake, people with advanced gastroparesis, and ALS. For long term use, gastric tubes appear to have better outcomes than nasogastric tubes.
People who have surgery on their throat or stomach often have a feeding tube while recovering from surgery; a tube leading through the nose and down to the middle part of the small intestine is used, or a tube is directly placed through the abdomen to the small intestine. As of 2017 it appeared that people with a tube through the nose were able to start eating normally sooner.
In case of Children
Feeding tubes are used widely in children with excellent success for a wide variety of conditions. Some children use them temporarily until they are able to eat on their own, while other children require them long-term. Some children only use feeding tubes to supplement their oral diet, while others rely on them exclusively.
Types of Tube Feedings
The most common types of tubes include those placed through the nose, including nasogastric, nasoduodenal, and nasojejunal tubes, and those placed directly into the abdomen, such as a gastrostomy, gastrojejunostomy, or jejunostomy feeding tube.
Nasogastric feeding tube
A nasogastric feeding tube or NG-tube is passed through the nares (nostril), down the esophagus and into the stomach. This type of feeding tube is generally used for short term feeding, usually less than a month, though some infants and children may use an NG-tube longterm. Individuals who need tube feeding for a longer period of time are typically transitioned to a more permanent gastric feeding tube. The primary advantage of the NG-tube is that it is temporary and relatively non-invasive to place, meaning it can be removed or replaced at any time without surgery. NG-tubes can have complications, particularly related to accidental removal of the tube and nasal irritation.
Nasojejunal feeding tube
A nasojejunal or NJ-tube is similar to an NG-tube except that it is threaded through the stomach and into the jejunum, the middle section of the small intestine. In some cases, a nasoduodenal or ND-tube may be placed into the duodenum, the first part of the small intestine. These types of tubes are used for individuals who are unable to tolerate feeding into the stomach, due to dysfunction of the stomach, impaired gastric motility, severe reflux or vomiting. These types of tubes must be placed in a hospital setting.
Gastrostomy or gastric feeding tube
A gastric feeding tube (G-tube or “button”) is a tube inserted through a small incision in the abdomen into the stomach and is used for long-term enteral nutrition. One type is the percutaneous endoscopic gastrostomy (PEG) tube which is placed endoscopically. The position of the endoscope can be visualized on the outside of the person’s abdomen because it contains a powerful light source. A needle is inserted through the abdomen, visualized within the stomach by the endoscope, and a suture passed through the needle is grasped by the endoscope and pulled up through the esophagus. The suture is then tied to the end of the PEG tubes that will be external, and pulled back down through the esophagus, stomach, and out through the abdominal wall. The insertion takes about 20 minutes. The tube is kept within the stomach either by a balloon on its tip (which can be deflated) or by a retention dome which is wider than the tract of the tube. G-tubes may also be placed surgically, using either an open or laparoscopic technique.
Gastric feeding tubes are suitable for long-term use, though they sometimes need to be replaced if used long-term. The G-tube can be useful where there is difficulty with swallowing because of neurologic or anatomic disorders (stroke, esophageal atresia, tracheoesophageal fistula, radiotherapy for head and neck cancer), and to decrease the risk of aspiration pneumonia. However, in people with advanced dementia or adult failure to thrive it does not decrease the risk of pneumonia. There is moderate quality evidence suggesting that the risk of aspiration pneumonia may be reduced by inserting the feeding tube into the duodenum or the jejunum (post-pyloric feeding), when compared to inserting the feeding tube into the stomach. People with dementia may attempt to remove the PEG, which causes complications.
What types of enteral feeding formula are there?
- Standard Formulas (whole protein formulas)
- Peptide Formulas (semi-elemental formulas)
- Specialised Formulas
Standard Formulas (whole protein formulas)
A standard tube-feeding formula is a formula that is designed for adults or children who have normal digestion. Standard formulas include all of the nutrients required to maintain health. Some standard formulas can be used for both enteral feeding and as an oral supplement. They can contain added ingredients, such as fibre, for digestive health and bowel management.
Peptide Formulas (semi-elemental formulas)
Like standard formulas, peptide formulas are nutritionally complete, which means they contain all the essential nutrients needed. However, unlike standard formulas, some of the components, such as protein are “broken down” into smaller components to make them easier to digest.
Peptide formulas are easier for the digestive system to digest and absorb, making them better suited for adults and children with digestive problems, including malabsorption, short bowel syndrome, inflammatory bowel disease, cystic fibrosis and other conditions that can cause problems with absorbing nutrients.
Specialised enteral formulas are available for adults and children with special nutritional needs, such as diabetes, kidney failure, respiratory disease, or liver disorders. The enteral formula should be selected by a doctor or a dietitian who is familiar with the various formulas.
Key Components of Enteral Nutrition Formulas
As with any food source, the key components of enteral nutrition include proteins, carbohydrates, and fats. The characteristics of these macronutrient components vary, however. For example, nutrient components may be hydrolyzed or broken down to varying degrees to aid in digestion. The protein component of enteral nutrition may be composed of polypeptides, oligopeptides (partially hydrolyzed), or free amino acids (fully hydrolyzed). Although short-chain polypeptides and oligopeptides are easily absorbed, free amino acids may not be absorbed efficiently.
The carbohydrate components of enteral nutrition may include polysaccharides, oligosaccharides, and fiber. Of these components, oligosaccharides can be absorbed. Carbohydrate polysaccharides, such as starch, may be broken down into simple sugars through enzymatic processes, while fiber may be fermented by gut bacteria to form short-chain fatty acids.
Isotonic formula is standard for enteral nutrition of critically ill patients, but nutrient dense formulas are preferred in some ICU settings to facilitate nutrient delivery using smaller fluid volumes. In the current study, the hospital formula that constitutes the most of patient’s feeding formula was low in density about half of density of ideal isotonic formula that made the patients away from the target calories and proteins as compared to ready-made formulas. This may be attributed to the lack of knowledge of the staff responsible for formula preparation about formula density and it’s relation with adequacy
Complications of tube feedings
Nasogastric and nasojejeunal tubes are meant to convey liquid food to the stomach or intestines. When inserted incorrectly, the tip may rest in the respiratory system instead of the stomach or intestines; in this case, the liquid food will enter the lungs, resulting in pneumonia and can, in rare cases, lead to death.
Complications associated with gastrostomy tubes (inserted through the abdomen and into the stomach or intestines) include leakage of gastric contents (containing hydrochloric acid) around the tube into the abdominal (peritoneal) cavity resulting in peritonitis, a serious complication which will cause death if it is not properly treated. Septic shock is another possible complication. Minor leakage may cause irritation of the skin around the gastrostomy site or stoma. Barrier creams, to protect the skin from the corrosive acid, are used to manage this.
A phenomenon called “tube dependency” has been discussed in the medical literature, in which a child refuses to eat after being on a feeding tube.
Parenteral nutrition (PN) is intravenous administration of nutrition, which may include protein, carbohydrate, fat, minerals and electrolytes, vitamins and other trace elements for patients who cannot eat or absorb enough food through tube feeding formula or by mouth to maintain good nutrition status. Achieving the right nutritional intake in a timely manner can help combat complications and be an important part of a patient’s recovery. Parenteral nutrition is sometimes called Total Parenteral Nutrition (TPN).
Parenteral feeding refers to giving nutrition through a person’s veins. You’ll have a type of venous access device, such as a port or a peripherally inserted central catheter (PICC or PIC line), inserted so you can receive liquid nutrition.
If this is your supplementary nutrition, it’s called peripheral parenteral nutrition (PPN). PN should only be initiated in patients who are hemodynamically stable and who are able to tolerate the fluid volume, protein, carbohydrate, and lipid doses necessary to provide adequate nutrients.When you’re getting all of your nutritional requirements through an IV, it’s often called total parenteral nutrition (TPN).
Parenteral feeding can be a life-saving option in many circumstances. However, it’s preferable to use enteral nutrition if at all possible. Enteral nutrition most closely mimics regular eating and can help with immune system function.
Who Receives Parenteral Nutrition?
The principal indication for TPN is a seriously ill patient where enteral feeding is not possible. It may also be used to supplement inadequate oral intake. The successful use of TPN requires proper selection of patients, adequate experience with the technique, and awareness of its complications. Some of the more important indications of TPN are listed below:
- Newborns with gastrointestinal anomalies such as tracheoesophageal fistula, massive intestinal atresia, complicated meconium ileus, massive diaphragmatic hernia, gastroschisis, omphalocele or cloacalexostrophy, and neglected pyloric stenosis.
- Failure to thrive in infants with short bowel syndrome, malabsorption, inflammatory bowel disease, enzyme deficiencies and chronic idiopathic diarrhea.
- Other paediatric indications include necrotizing enterocolitis, intestinal fistulae, severe trauma, burns, postoperative infections and malignancies.
- Adults with short bowel syndrome secondary to massive small-bowel resection or internal or external enteric fistulae.
- Malnutrition secondary to high intestinal obstruction for example achalasia, oesophageal strictures and neoplasms, pyloric obstruction and gastric neoplasms.
- Prolonged ileus due to medical or surgical causes (for example post-operative, following abdominal trauma or polytrauma).
- Malabsorption secondary to sprue, enzyme & pancreatic deficiencies, regional enteritis, ulcerative colitis, granulomatous colitis, and tuberculous enteritis.
- Functional gastrointestinal disorders like idiopathic diarrhoea, psychogenic vomiting, anorexia nervosa.
- Patients with depressed sensorium (for example following head injury or intracranial surgery) in whom tube feeding is not possible.
- Hypercatabolic states secondary to severe sepsis, extensive full thickness burns, major fractures, polytrauma, major abdominal operations etc.
- Patients with malignancies in whom malnutrition may jeopardize successful delivery of a therapeutic option (surgery, chemo- or radiotherapy).
- Paraplegics/quadriplegics with pressure sores in pelvic or perineal regions where fecal soiling is a problem.
Nutritional Requirements and Delivery of TPN
The delivery of TPN is via a large bore central venous catheter placed in the superior vena cava through the subclavian or the internal jugular vein. This can be done by a “cut-down”, but it is much better to use one of the modern percutaneous catheter-systems, as the incidence of infection is much lower by the use of the latter technique. Strict asepsis is to be observed during the placement of the catheter. A chest radiograph should be taken prior to the commencement of feeding to confirm the position of the catheter-tip and to exclude traumatic pneumothorax, the commonest complication related to catheter placement. The catheter should be flushed with dilute heparin daily, to avoid catheter thrombosis. With proper care, a central catheter can be maintained for several days or even weeks for the delivery of TPN.
While energy requirements can be calculated by the Harris-Benedict equation or the Long’s modification of the same , in practice the institution of TPN is not so complicated. The therapy is now well standardized, yet it allows a fair deal of freedom to the treating physician. However, certain basic principles must be adhered to. The ratio of calories to nitrogen must be adequate (at least 100 to 150 kcal/g nitrogen) and the two materials must be infused simultaneously as there is significant decrease in nitrogen utilization if they are infused at different times. The entire TPN requirement for the day should be constituted in the hospital pharmacy under strict aseptic conditions. The basic solution should contain 20% to 25% dextrose and 3% to 5% crystalline amino acids from the commercially available kits/solutions. Lipid emulsions are not only an important source of energy, but also prevent development of essential fatty acid deficiency. While there are several special formulations available for specific clinical situations, an outline of basic TPN solution is given below.
Fluid requirements : 100 mL/kg body weight for the first 10 kg, 50 mL/kg for next 10 kg and 20 mL/kg for each additional kg of body weight. Compensations should be made for additional losses e.g., from a fistula.
Calories: Glucose is the major carbohydrate which supplies calories, and this is administered in the form of 25% or 50% solution. Total energy requirement may vary considerably between 2000 to 4500 or more calories daily.
Fats: In order to avoid essential fatty acid deficiency at least 4% of calories should be supplied as fats.
Proteins: Protein requirement varies from 1.5 to 2.5 g/kg of body weight per day. The ratio of nitrogen to calories should be 1: 100–150. Branched-chain amino acids have been recommended as an integral part of TPN. However their benefits have so far not been conclusively proved.
Electrolytes: Daily maintenance requirements of sodium are 1–1.5 mEq/kg; potassium 1 mEq/kg; chloride 1.5–2 mEq/kg; calcium 0.2 mEq/kg and magnesium 0.35 – 0.45 mEq/kg.
Micronutrients: Trace elements are an important component of TPN. Zinc 5 mg, copper 1 mg, chromium 10 mcg, manganese 0.5 mg and iron 1–2 mg are required daily.
Vitamins: Vit K-1 10 mg and folic acid 5 mg should be administered intramuscularly once a week. Vit B-12 1 mg is given once a month. Water soluble vitamins should be given daily.
Nutritional monitoring: It is recommended that the following parameters be measured daily during TPN: Body weight estimation; 12-hourly intake-output chart; 8-hourly urine-sugar estimation; serum sodium, potassium, bicarbonate, calcium and chloride; blood urea and serum creatinine. Liver function tests and serum proteins should be measured twice daily.
Enteral Nutrition v/s Parenteral Nutrition
Enteral nutrition is preferred over parenteral nutrition, as use of total parenteral nutrition (TPN) therapy is complex and has been associated with increased complications and higher costs.Complications associated with TPN include line-associated infections, vascular thrombosis, cholestastic liver disease, metabolic bone disease, and cholelithiasis.Additionally, close and frequent monitoring of patients on TPN is required due to the possibility of electrolyte imbalances and fluid overload. Depsite these risks for certain patient groups, including patients with intestinal failure, short bowel syndrome, severe fixed intestinal obstructions, or fistulas not amenable to enteral nutrition, parenteral nutrition may be necessary to achieve adequate nutritional status. Finally, TPN does not promote restoration of normal gastrointestinal digestive functions.
In general, enteral nutrition is preferred to parenteral nutrition as it is more physiological, simpler, cheaper and less complicated. However even nasogastric feeding needs care and the more complex types of enteral nutrition such as gastrostomy and jejunostomy need significant interventions. It is therefore important that any institution using artificial nutrition follows strict protocols and procedures for its use.
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