Specialized nutrition support

Specialized nutrition support comprises the administration of enteral nutrition (bypassing the oropharynx) and/or parenteral nutrition (bypassing the GI tract). Specialized nutrition support is primarily indicated in patients with malnutrition and those at high nutritional risk. Enteral nutrition is preferred over parenteral nutrition unless contraindications to enteral nutrition are present (e.g., mechanical bowel obstruction). Nutrition support is associated with various complications such as injury during feeding tube placement, IV catheter-related infection, and metabolic complications. There is a higher risk of metabolic complications with parenteral nutrition than with enteral nutrition.

General principles ^[1][2]

• Consult a nutritionist if available. ^[3]
• Consider specialized nutrition support in:
  • Hospitalized patients who are both: ^[2]
    • At high nutritional risk or diagnosed with malnutrition
    • Unable to maintain nutritional status with oral intake
  • Critically ill patients unable to maintain oral intake ^[4]
• Specialized nutrition support is usually not indicated in well-nourished adults who are both: ^[3]
  • At low nutritional risk
  • Expected to resume oral intake within 5–7 days
• Use clinical judgment and follow local protocols.

Nutritional risk assessment ^[2]

• Nutritional risk is based on both:
  • Nutritional status
  • Disease severity
• Consider the use of validated screening tools, e.g.:
  • Nutrition Risk Screening 2002 score (NRS-2002 score)
  • Nutrition Risk in the Critically Ill score (NUTRIC score)

Common causes of malnutrition in adults ^[5]

Conditions that may lead to malnutrition include:

• Restricted oral intake
  • Mechanical ventilation
  • Coma or altered mental status
  • Early postoperative state ^[6]
  • Dysphagia (e.g., secondary to stroke or esophageal carcinoma)
• Severe anorexia
  • Malignancy or chemotherapy-associated
  • Anorexia nervosa
• Increased metabolic demands
  • Advanced chronic illness (e.g., cystic fibrosis, COPD)
  • Acute critical illness
  • Enterocutaneous fistula
• Severe malabsorption
  • Chronic inflammatory bowel diseases
  • Short bowel syndrome

Considerations for enteral vs. parenteral nutrition ^[3][7][8]

• Enteral nutrition: first choice for most patients
  • Lower risk of metabolic complications and bloodstream infection than with parenteral nutrition
  • Intestinal motility is stimulated, preventing mucosal atrophy.
• Parenteral nutrition: second line if enteral nutrition is contraindicated, not tolerated, or insufficient to meet metabolic needs
• Use shared decision-making and consider:
  • Goals of care (e.g., patient preference for minimal interventions)
  • Impact on quality of life, especially in patients with a limited life expectancy

Enteral feeding has not been shown to increase survival or improve quality of life in patients with dementia. ^[3]

The following principle applies to most situations: oral before enteral, enteral before parenteral!

Enteral feeding is first choice for most patients with indications for specialized nutrition support.

Definition

Enteral nutrition is the administration of nutrients via a feeding tube placed directly into the stomach, duodenum, or jejunum.

Routes ^[2]

Nasal or oral access

• Gastric feeding: preferred initial route
  • Nasogastric tube
  • Orogastric tube
• Postpyloric feeding, e.g., nasojejunal tube, nasoduodenal tube

Percutaneous access

Percutaneous access is indicated if nutritional support is anticipated for approx. > 4 weeks and inserted surgically, fluoroscopically, or endoscopically.

• Gastrostomy tube (G tube) ^[9][10]
  • Inserted into the stomach through an incision in the abdominal wall
  • Example: endoscopically inserted percutaneous endoscopic gastrostomy (PEG) tube
• Jejunostomy tube (J tube)
  • Inserted into the jejunum through an incision in the abdominal wall
  • Used if gastric enteral feeding is contraindicated
• Gastrojejunostomy tube (GJ tube)
  • Inserted into the stomach through an incision in the abdominal wall, with an additional tube threaded into the jejunum
  • Used to provide postpyloric feeding and to vent the stomach

Contraindications ^[7][11]

• Acute abdomen (e.g., peritonitis)
• GI tract dysfunction, e.g.:
  • Mechanical bowel obstruction or paralytic ileus
  • Internal or external intestinal fistulae
  • Upper GI bleeding
  • Intractable vomiting or diarrhea
• Pediatric conditions
  • Congenital visceral anomalies (e.g., gastroschisis)
  • Necrotizing enterocolitis
• Radiation enteritis

Absolute contraindications for enteral nutrition include mechanical bowel obstruction and severe bowel ischemia. ^[1][2]

Aspiration prevention ^[3][11][12]

• Ensure adequate tube type and placement.
  • Use chest x-ray or ultrasound to verify correct gastric or postpyloric tube position.
  • Air insufflation followed by epigastric auscultation can be used if access to radiography is limited.
• Consider postpyloric feeding if patients experience adverse effects (e.g., recurrent emesis, gastroparesis).
• Ensure correct patient positioning: Elevate the head of the bed to > 30°.
• Consider prokinetic agents to promote gastric emptying.

Tube feeding regimens ^[11]

• Continuous feeding
  • The typical initial infusion rate is 50 mL/hour.
  • Increase the rate of infusion by 25 mL/hour every 4–8 hours until the target rate is reached.
• Bolus feeding (gastric feeding only)
  • 200–400 mL of formula multiple times per day
  • Hold if there is residual tube feed formula in the gastric body 4 hours after the previous bolus.

Composition of enteral feeding solutions ^[3][11][13]

Solution compositions vary based on individual patient needs and should be selected in consultation with a nutritionist.

• Feeding solutions typically include:
  • Proteins: e.g., amino acids, peptides, high-molecular-weight proteins
  • Carbohydrates: e.g., mono-, oligo-, polysaccharides
  • Fats: e.g., medium- or long-chain fatty acids
  • Other: Electrolytes, trace elements, and vitamins are added according to the recommended daily intake.
• Osmolality of enteral feeds: ∼ 300 mOsmol/L

Enteral nutrition-specific complications ^[3][7][11]

Nutrition related

• Gastrointestinal complications
  • Osmotic diarrhea (most common complication)
  • Nausea, vomiting, bloating
  • Gastroesophageal reflux
• Respiratory complications
  • Aspiration pneumonia
  • Aspiration pneumonitis
  • Respiratory failure due to enteral feeding: Aspiration and the increased carbon dioxide production associated with enteral nutrition can lead to hypercapnia and respiratory failure. ^[14][15]
• Other: metabolic complications of specialized nutrition support

Access related

• Tube blockage or dislodgement
• NG tube-specific ^[16]
  • Incorrect placement, e.g., in the trachea
  • Injury to or perforation of the stomach wall
  • Erosion of the nares
• G tube-specific ^[17]
  • Peristomal infection and/or leakage
  • Buried bumper syndrome
  • Bowel perforation
  • Bleeding

Management of G tube complications ^[9][10]

• All patients with complications
  • Stop tube feed.
  • Consult specialty service, e.g., surgery, interventional radiology.
• Tube blockage ^[18]
  • Instill warm water with a 30–60 mL syringe and apply gentle back-and-forth pressure on the plunger. ^[18]
  • If unsuccessful: Instill activated pancreatic enzyme solution, clamp the G tube, and reattempt flushing after 30 minutes.
  • If the obstruction remains, consider using a declogging brush and/or tube replacement.
• Infection: Consider antibiotics.
  • Signs of peritonitis: empiric antibiotics for intraabdominal infections ^[10]
  • Local peristomal infection: empiric antibiotics for SSTIs ^[10]
• Early dislodgement (< 4 weeks after placement)
  • Endoscopic replacement is usually required.
  • Do not attempt blind reinsertion.
  • Admit for specialist consult and monitor for signs of peritonitis.
• Late dislodgement (> 4 weeks after placement)
  • Bedside G tube replacement can be safely attempted for late dislodgement. ^[10]
  • Place a new G tube or, if a new G tube is not immediately available, a foley catheter. ^[10][19]
  • Inflate the gastrostomy tube balloon and confirm correct placement before resuming tube feed. ^[19]

Do not attempt to unclog a G tube with forceful irrigation or carbonated beverages, as this can worsen occlusion and/or lead to tube rupture. ^[19]

For tube dislodgement > 4 weeks after placement, immediately stent the tract with a new G tube or a foley catheter to prevent tract closure. ^[10]

Definition ^[11]

• Parenteral nutrition: the intravenous delivery of nutrition, bypassing the GI tract
• Total parenteral nutrition (TPN): the intravenous provision of all nutritional requirements
• Supplemental parenteral nutrition: the intravenous provision of nutrients to augment oral intake and meet nutritional goals

Indications ^[8]

Enteral nutrition is either:

• Not tolerated
• Contraindicated, e.g., due to mechanical bowel obstruction, intestinal fistula
• Insufficient to meet metabolic needs, e.g., due to short bowel syndrome, severe chronic inflammatory bowel disease

Routes ^[3][8]

• Central venous access
  • Preferred for most patients
  • Options include:
    • Peripherally inserted central catheter (PICC line)
    • Tunneled central venous catheter (e.g., Hickman line)
    • Implanted port
• Peripheral venous access: may be considered if parenteral nutrition is expected to be required for ≤ 2 weeks and the patient can tolerate large volumes of low osmolarity formula (e.g., 600–900 mOsm/L) ^[2][8]

Standard concentrations of total parenteral nutrition formulas (typically > 1800 mOsm/L) are caustic to veins and therefore better tolerated with central venous administration. ^[3]

Contraindications ^[3]

• Enteral nutrition is feasible and can meet metabolic demands
• Severe electrolyte abnormalities
• Volume overload
• Hyperglycemia: serum glucose > 300 mg/dL (> 16.65 mmol/L) ^[3]

Infusion regimens ^[20]

• Continuous parenteral nutrition
  • Set rate over 24 hours
  • Commonly used in acute care settings
  • Higher risk of hepatic steatosis than cyclic
• Cyclic parenteral nutrition
  • Infused over 10–14 hours (as tolerated)
  • Allows for bolus administration at night (e.g., at the patient's home)
  • Higher risk of fluid overload, hyperglycemia, and electrolyte imbalances than continuous

Composition of parenteral feeding solutions ^[11]

• Proteins: amino acids
• Carbohydrates: mostly glucose
• Fats: medium-chain fatty acids in a fat emulsion
• Other: Electrolytes, trace elements, and vitamins are added according to the recommended daily intake.

Parenteral nutrition-specific complications ^[11]

• Nutrition-related
  • Metabolic complications of specialized nutrition support
  • Intestinal failure-associated liver disease
  • Fluid overload
• Access-related
  • Venous thrombus, venous embolism
  • Catheter-related bloodstream infection
  • Catheter displacement
  • Iatrogenic injury, e.g., pneumothorax

• Hyperglycemia during enteral or parenteral nutrition
• Refeeding syndrome with associated electrolyte imbalances, e.g.:
  • Hypophosphatemia
  • Hypomagnesemia
  • Hypokalemia
• Reduced bone mineral density
• Hepatic and biliary dysfunction
  • Nonalcoholic fatty liver disease
  • Gallstone disease, acalculous cholecystitis, cholestasis
• Hyperlipidemia

Metabolic complications are more common with parenteral nutrition than with enteral nutrition!

• Definition
  • Liver dysfunction caused by the medical and surgical treatments for intestinal failure
  • Parenteral nutrition-associated cholestasis (PNAC): intrahepatic cholestasis due to prolonged parenteral nutrition (> 2 weeks)
• Epidemiology: common in neonates, especially preterm infants
• Risk factors
  • Parenteral nutrition: inappropriate use of lipid emulsions, lack of antioxidants, aluminum toxicity, prolonged infusion periods (> 2 weeks)
  • Prematurity
  • Small for gestational age
  • Low birth weight
  • Intestinal malformations (e.g., of the small bowel)
  • Necrotizing enterocolitis
  • Early or recurrent sepsis
  • Intestinal surgery (e.g., prolonged maintenance of stomas)
• Clinical features: jaundice
• Diagnostics
  • Medical history: prolonged parental nutrition, intestinal failure, unexplained cholestasis
  • Elevated serum direct bilirubin
    • ≥ 1 mg/dL: early sign of liver injury
    • ≥ 2.0 mg/dL: indicates cholestatic liver disease
  • Elevated AST, ALT, GGT
• Treatment ^[21]
  • Medical treatment
    • Ursodeoxycholic acid
    • Maximizing enteral feedings: early initiation and progressive increase of feedings
    • Parenteral nutrition management: cyclical infusions, tapering soybean lipid emulsion, light protection for parenteral nutrition bag
    • Antibiotics
  • Surgical treatment
    • Bowel lengthening procedures (if applicable)
    • Transplantation: liver transplantation or liver and intestinal transplantation