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 
- Consult a nutritionist if available. 
- Consider specialized nutrition support in:
- Specialized nutrition support is usually not indicated in well-nourished adults who are both: 
- At low nutritional risk
- Expected to resume oral intake within 5–7 days
- Use clinical judgment and follow local protocols.
Nutritional risk assessment 
- Nutritional risk is based on both:
- Nutritional status
- Disease severity
- Consider the use of validated screening tools, e.g.:
Common causes of malnutrition in adults 
Conditions that may lead to malnutrition include:
- Restricted oral intake
- Severe anorexia
- Increased metabolic demands
- Severe malabsorption
Considerations for enteral vs. parenteral nutrition 
- Enteral nutrition: first choice for most patients
- Parenteral nutrition: second line if enteral nutrition is contraindicated, not tolerated, or insufficient to meet metabolic needs
- Use and consider:
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.
Nasal or oral access
- Gastric feeding: preferred initial route
- Postpyloric feeding, e.g., nasojejunal tube, nasoduodenal tube
Percutaneous access is indicated if nutritional support is anticipated for approx. > 4 weeks and inserted surgically, fluoroscopically, or endoscopically.
- Gastrostomy tube (G tube) 
- Jejunostomy tube (J tube)
- Gastrojejunostomy tube (GJ tube)
- (e.g., peritonitis)
- GI tract dysfunction, e.g.:
- Pediatric conditions
- Radiation enteritis
Absolute contraindications for enteral nutrition include and severe . 
Aspiration prevention 
- Ensure adequate tube type and placement.
- 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 to promote gastric emptying.
Tube feeding regimens 
- 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 4 hours after the previous bolus.
Composition of enteral feeding solutions 
Solution compositions vary based on individual patient needs and should be selected in consultation with a nutritionist.
- Feeding solutions typically include:
- Osmolality of enteral feeds: ∼ 300 mOsmol/L
Enteral nutrition-specific complications 
- Gastrointestinal complications
- Respiratory complications
- Tube blockage or dislodgement
- NG tube-specific 
- G tube-specific 
Management of G tube complications 
All patients with complications
- Stop tube feed.
- Consult specialty service, e.g., surgery, interventional radiology.
Tube blockage 
- Instill warm water with a 30–60 mL syringe and apply gentle back-and-forth pressure on the plunger. 
- 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: 
- Local peristomal infection: 
Early dislodgement (< 4 weeks after placement)
- Endoscopic replacement is usually required.
- Do not attempt blind reinsertion.
- Admit for specialist consult and monitor for .
- Late dislodgement (> 4 weeks after placement)
- 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
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
- Central venous access
- parenteral nutrition is expected to be required for ≤ 2 weeks: may be considered if and the patient can tolerate large volumes of low osmolarity formula (e.g., 600–900 mOsm/L) 
- Enteral nutrition is feasible and can meet metabolic demands
- Severe electrolyte abnormalities
- Volume overload
- Hyperglycemia: serum glucose > 300 mg/dL (> 16.65 mmol/L) 
Infusion regimens 
Continuous parenteral nutrition
- Set rate over 24 hours
- Commonly used in acute care settings
- Higher risk of hepatic steatosis than cyclic
- Cyclic parenteral nutrition
Composition of parenteral feeding solutions 
- 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 
- Hyperglycemia during enteral or parenteral nutrition
- with associated electrolyte imbalances, e.g.:
- Hepatic and biliary dysfunction
- Epidemiology: common in neonates, especially preterm infants
- Parenteral nutrition: inappropriate use of lipid emulsions, lack of antioxidants, aluminum toxicity, prolonged infusion periods (> 2 weeks)
- 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
- Medical treatment
- Surgical treatment