What are the recommended strategies for supplemental nutrition in adult patients with inadequate dietary intake, including oral, enteral, and parenteral options?

Supplemental Nutrition: A Hierarchical Approach

Start with oral nutritional supplements (ONS) as first-line therapy, escalate to enteral tube feeding if oral intake remains inadequate, and reserve parenteral nutrition only when the gastrointestinal tract is non-functional or inaccessible. 1

When to Initiate Nutritional Support

Begin artificial nutrition support when oral intake is absent or likely to be absent for 5-7 days in normally nourished patients. 2 In malnourished patients, start earlier—within 1-2 days for severely malnourished, 3-5 days for moderately malnourished patients. 2

• Patients anticipated to be unable to ingest or absorb adequate nutrients for more than 1-2 weeks are candidates for artificial nutrition. 2
• If patients are consuming less than 60% of estimated energy requirements for more than 10 days, nutritional support should be initiated. 2
• Delay intervention if patients are taking 50% or more of estimated nutritional requirements. 2

Step 1: Oral Nutritional Supplements (ONS)

ONS are mandatory as the first step when artificial nutrition is indicated, providing up to 600 kcal/day without compromising normal food intake. 1

• Start ONS when patients cannot meet energy needs from normal food alone. 1
• Continue ONS as long as oral intake remains possible, even if inadequate. 1
• In cancer patients, personalized dietetic counseling combined with ONS improves nutritional intake, quality of life, and stabilizes body weight. 2
• ONS may reduce post-operative complications and weight loss in patients undergoing chemotherapy. 2

Step 2: Enteral Tube Feeding

Initiate tube feeding only when oral feeding (including ONS) is insufficient to meet nutritional requirements. 1

• Enteral feeding should always take preference over parenteral feeding unless completely contraindicated. 1
• If intestinal functions are preserved, enteral feeding is as efficient as parenteral feeding with lower complication rates. 2
• Early post-pyloric enteral feeding is safe and effective even in the presence of apparent ileus. 2
• In head and neck cancer patients, nasogastric tubes may have lower complication rates than PEG tubes while maintaining high success rates. 2

Specific Indications for Enteral Feeding:

• Unconscious patients, those with swallowing disorders, and those with partial intestinal failure. 2
• Patients with tumors impairing oral intake or food transport in the upper gastrointestinal tract. 2
• Early enteral feeding after major gastrointestinal surgery reduces infections and shortens hospital stay. 2

Step 3: Parenteral Nutrition (PN)

Reserve parenteral nutrition for situations where the gastrointestinal tract is non-functional, inaccessible, or when enteral routes have failed. 1

Absolute Indications:

• Gastrointestinal tract dysfunction or short bowel syndrome. 1
• Obstructed bowel or surgical complications. 1
• Severe intestinal insufficiency due to radiation enteritis, chronic bowel obstruction, peritoneal carcinosis, or chylothorax. 2
• Severe malnutrition requiring preoperative support when enteral routes are inadequate. 1

Critical Timing for PN:

• In severely malnourished surgical patients, administer PN for 7-14 days preoperatively, which reduces complications from 45% to 28%. 1
• Do not use PN in well-nourished patients preoperatively—it provides no benefit. 1
• In geriatric patients, offer PN only to those with reasonable prognosis when oral and enteral intake are impossible for more than 3 days or below half requirements for more than 1 week. 1

Common Pitfalls and How to Avoid Them

Refeeding Syndrome Prevention:

In severely malnourished patients requiring PN, increase feeding gradually over the first 3 days with laboratory and cardiac monitoring. 1

• Monitor and replace potassium, magnesium, phosphate, and thiamine even with mild deficiency. 1, 3
• Administer vitamin B1 (thiamine) prior to starting glucose infusion to reduce risk of Wernicke's encephalopathy. 3, 4
• Regular blood glucose monitoring is essential to detect hypoglycemia and avoid hyperglycemia. 3

Avoiding Inappropriate PN Use:

• Never use PN as first-line therapy when the GI tract is functional. 1
• Routine PN in cancer patients during chemotherapy shows no survival benefit and increases complications by 40%, infections by 16%, and decreases tumor response. 2
• There is no place for indiscriminate use of artificial nutrition in all cancer patients as a "routine" adjunct to cytotoxic therapy. 2

Proper PN Composition:

• Complete nutritional support requires balanced energy (1.3x Resting Energy Expenditure), with glucose covering 50-60% of non-protein energy. 3
• Amino acids should be provided at 1.2-1.5 g/kg/day. 3
• Water-soluble vitamins and trace elements should be given daily from the first day. 3
• Using D50 alone without addressing protein, lipid, and micronutrient needs is harmful. 3

Special Populations

Cancer Patients:

• In patients undergoing curative anticancer treatment, if oral intake is inadequate despite counseling and ONS, use supplemental enteral or parenteral nutrition. 2
• Weight stabilization in gastro-intestinal and lung cancer patients correlates with significant improvements in survival. 2
• An individualized nutrition intervention program escalated from counseling to ONS to enteral tube feeding to PN as required to avoid caloric deficit was associated with improved body weight and survival in malignancy-related cachexia. 2

Dialysis Patients:

• If enteral feedings are not used, consider intradialytic parenteral nutrition (IDPN) for hemodialysis or intraperitoneal amino acids (IPAA) for peritoneal dialysis if either approach in conjunction with existing oral intake meets protein and energy requirements. 2
• If the combination of oral intake and IDPN or IPAA does not meet requirements, daily total or partial parenteral nutrition should be considered. 2