Specialized nutrition support

Specialized nutrition support (SNS) is required when oral intake is either limited or not possible for a prolonged period of time. Common indications for SNS include patients in critical care, those with dysphagia, unconscious patients who cannot be fed, severely malnourished patients, and those with intestinal malabsorption. The two forms of SNS are enteral nutrition and parenteral nutrition. Enteral feeding is always preferred whenever possible, but parenteral feeding may be instituted if the patient has a nonfunctional GI tract (e.g., gastroschisis, short bowel syndromes), and/or if enteral feeding is contraindicated. Patients who are on SNS may develop several complications related to feeding tubes or intravenous catheters, as well as additional metabolic complications such as electrolyte imbalances, hyperglycemia, refeeding syndrome, gallstone disease, and nonalcoholic fatty liver disease.

• Dysphagia; (e.g., post-stroke state; , multiple sclerosis, esophageal carcinoma)
• Patients with a low GCS who cannot be fed
• Difficulty with oral intake in the early postoperative state
• Severe anorexia (e.g., terminally ill cancer patients, anorexia nervosa)
• Severe malnutrition
• Critically-ill patients
• Intestinal malabsorption

References: ^[1]

• First-line: enteral feeding
  • Advantages
    • Easier to perform
    • Metabolic complications occur less often
    • Intestinal motility is stimulated, preventing mucosal atrophy
    • Lower risk of blood stream infection
• Second-line: parenteral feeding

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

Definition

Administration of nutrients directly into the stomach, duodenum, or jejunum with the help of feeding tubes

Indications ^[2][3]

• Acute respiratory failure requiring intensive care
• Mechanically ventilated patients
• Comatose patients (e.g., due to severe head injury)
• Impaired swallowing (e.g., neuromuscular disorders like multiple sclerosis, cerebral palsy, stroke)
• Anorexia or wasting syndrome (e.g., from chemotherapy, HIV)
• Impaired gastrointestinal absorption or upper gastrointestinal obstructions (e.g., short bowel syndrome, inborn errors of metabolism, esophageal strictures, esophageal tumor)
• Increased metabolic demands (e.g., sepsis, cystic fibrosis, burns, bronchopulmonary dysplasia)

Contraindications

• Mechanical ileus, bowel obstruction
• Acute abdomen (e.g., severe pancreatitis, peritonitis)
• Upper GI bleeding
• Intractable vomiting or diarrhea
• Mucositis, radiation enteritis
• Severe substrate malabsorption
• Congenital GI anomalies
• High-output fistulas
• Nonfunctional GI tract (e.g., gastroschisis, short bowel syndromes)

Routes ^[2]

• Short-term: nasogastric tube , nasoduodenal, nasojejunal, orogastric, oroduodenal, or orojejunal
• Long-term (> 2–3 weeks):
  • Gastrostomy tube: gastric feeding tube inserted endoscopically through a small incision through the abdomen into the stomach (e.g., percutaneous endoscopic gastrostomy, percutaneous radiologic gastrostomy, surgically placed gastrostomy)
  • Jejunostomy tube: feeding tube inserted through a small incision through the abdomen into the jejunum to bypass the distal small bowel and/or colon (e.g., percutaneous endoscopic jejunostomy, percutaneous radiologic jejunostomy)

Composition of enteral feeding solutions

• Protein supply: amino acids/peptides / high-molecular-weight proteins
• Carbohydrate supply: mono-, oligo- or polysaccharides
• Fat supply: medium or long-chain fatty acids.
• Osmolality of enteral feeds: approximately 300 mOsmol/L
• Electrolytes, trace elements, and vitamins are added according to the recommended daily intake (see “Nutritional requirements during SNS” below).

Complications

Enteral nutrition-associated respiratory failure ^[1][4][5]

• Definition: a complication of enteral feeding resulting in respiratory failure due to aspiration and increased carbon dioxide production
• Pathophysiology
  • Aspiration → nosocomial pneumonia (small-volume aspirations) or respiratory failure (large-volume aspirations)
  • Increased carbon dioxide production associated with nutrition; → hypercapnia → respiratory distress and acute respiratory failure (especially in patients with COPD)
• Prevention
  • Correct patient positioning (semirecumbent position, Fowler position, semi-Fowler position).
  • Ensure adequate tube type and placement.
  • Use formulations with an adequate carbohydrate:fat ratio to avoid excessive total caloric intake.
  • Promote gastric emptying using motility agents (e.g., metoclopramide).

Other complications ^[1][5]

• Diarrhea
• Metabolic complications of specialized nutrition support
• Feeding tube-related
  • Blockage of the feeding tube
  • Nasogastric tube
    • Accidental placement of the tube inside the trachea
    • Injury to or perforation of the stomach wall
  • Gastrostomy or jejunostomy
    • Peristomal infection
    • High-output fistulas
• Gastroesophageal reflux

Definition ^[1]

• Intravenous administration of nutrients that bypasses the gastrointestinal tract
• Total parenteral nutrition: provision of all nutritional requirements intravenously without using the gastrointestinal tract

Indications for total parenteral nutrition ^[6]

Total parenteral nutrition should only be considered in patients without a functioning GI tract or when complete bowel rest is indicated.

• GI anomalies
  • Severe bowel obstruction (e.g., achalasia, esophageal strictures)
  • Short bowel syndrome
  • Internal or external enteric fistulae
• Severe malabsorption due to chronic inflammatory bowel diseases (e.g., Crohn disease, ulcerative colitis)
• Malignancies associated with severe malnutrition
• Congenital GI anomalies (e.g., gastroschisis, tracheoesophageal fistula, severe intestinal atresia)
• Necrotizing enterocolitis

Contraindications

• Enteral nutrition is feasible
• Serum hyperosmolality
• Severe hyperglycemia
• Severe electrolyte abnormalities
• Volume overload

Routes

• Parenteral nutrition is required for < 2 weeks: peripheral venous line, or peripherally inserted central catheter
• Parenteral nutrition is required for > 2 weeks: tunneled central venous catheter or a port

Regimens

• Continuous parenteral nutrition
  • Most commonly used, especially in hospital settings
  • Slower infusion rate
  • Higher risk of fatty liver
• Cyclical parenteral nutrition
  • TPN is given mostly at night
  • Faster infusion rates
  • Advantage: allows TPN in an outpatient setting
  • Disadvantage: higher risk of fluid overload, electrolyte imbalances, and unstable glucose levels
• Composition of parenteral feeding solutions
  • Protein supply: amino acids
  • Carbohydrate supply: mostly glucose
  • Fat supply: medium-chain fatty acids in a fat emulsion
  • Osmolality of parenteral feeds: 1000–2000 mOsmol/L
  • Electrolytes, trace elements, and vitamins are added according to the recommended daily intake.

Complications

Intestinal failure-associated liver disease (IFALD) ^[7]

• 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, GGTP
• Treatment ^[8]
  • 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

Other complications

• Venous catheter-related:
  • Catheter displacement
  • Thrombosis and/or embolism
  • Catheter-related bloodstream infection
• Fluid overload
• Metabolic complications of specialized nutrition support

• Severe electrolyte imbalances (e.g., hypocalcemia, hypomagnesemia, hypophosphatemia)
• Hyperglycemia
• Refeeding syndrome
• Bone demineralization
• Acalculous cholecystitis
• Gallstone disease
• Non-alcoholic fatty liver disease
• Renal damage
• Hyperlipidemia

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