How should I prescribe nutrition through a nasogastric (NG) tube?

Prescribing Nutrition Through a Nasogastric Tube in the ICU

Start enteral nutrition within 24 hours of NG tube placement at a low rate of 10-20 mL/hour using a standard whole protein formula, then increase by 20 mL/hour increments every 24 hours based on tolerance, targeting full nutritional requirements by day 5-7. 1, 2

Timing of Initiation

• Begin enteral nutrition within 24-48 hours of ICU admission once NG tube position is radiographically confirmed 1, 2, 3
• Early feeding (within 24 hours) is mandatory in patients who cannot eat orally and will have inadequate oral intake (<50%) for more than 7 days 1
• Do not delay feeding for hemodynamic stability unless the patient has escalating vasopressor requirements or uncontrolled shock 2, 3
• Feeding can be safely initiated even during treatment with small to moderate doses of vasopressor agents 3

Starting Rate and Advancement Protocol

Initial Rate:

• Start at 10-20 mL/hour with a standard polymeric formula 1, 2, 4
• Use full-strength formula immediately—do not dilute feeds or use starter regimens in patients with recent adequate nutritional intake 2

Advancement Schedule:

• Increase by 20 mL/hour increments every 24 hours based on individual tolerance 1, 4
• Expect to reach target intake in 5-7 days, though this varies significantly between patients 1, 4
• Monitor closely for signs of intolerance (nausea, vomiting, abdominal distension, diarrhea) before each rate increase 2, 3

Formula Selection

• Use a standard whole protein polymeric formula for most ICU patients 1
• No evidence supports routine use of elemental, semi-elemental, or immune-modulating formulas over standard formulas 1
• Avoid home-made or blenderized diets due to tube clogging risk, infection risk, and nutritional inconsistency 1, 4

Energy and Protein Targets

Energy Prescription:

• During the acute phase (days 1-3): Provide less than 18 kcal/kg/day or approximately 50-70% of estimated requirements in patients with low nutritional risk 2, 5
• After day 4-7: Calculate energy delivery to match expenditure, using 25-30 kcal/kg/day as a reasonable target 2, 5
• A starting point of 30 mL/kg/day of standard 1 kcal/mL feed is reasonable, though may be excessive in severely malnourished patients 2

Protein Prescription:

• Provide maximum 0.8 g/kg/day during the early acute phase 3
• During the rehabilitation phase: Target >1.2 g/kg/day 3

Critical Safety Considerations

Position Verification:

• Radiographic confirmation is mandatory before initiating any feeding 2
• Bedside auscultation is unreliable (sensitivity 79%, specificity 61%) and dangerous 2
• Tubes can enter the lung, pleural cavity, or coil in the esophagus if position is not confirmed 2

Patient Positioning:

• Maintain head of bed at ≥30 degrees during feeding and for 30 minutes after bolus feeds to minimize aspiration risk 2

Refeeding Syndrome Prevention:

• Assess refeeding risk in all malnourished patients 2
• Measure plasma phosphate daily during the first week 3
• If phosphate drops by 30%, reduce feeding rate and administer high-dose thiamine 3
• In severely malnourished patients, start at 50-70% of target and advance gradually over 3-5 days 2

Monitoring for Intolerance

Gastric Intolerance:

• Vomiting and increased gastric residual volume indicate gastric intolerance 3
• If intolerance develops, use prokinetic agents (erythromycin or metoclopramide) before considering post-pyloric feeding 6, 7

Lower GI Intolerance:

• Sudden abdominal pain, distension, gastrointestinal paralysis, or rising abdominal pressure indicate lower GI intolerance 3
• These signs may warrant temporary cessation of feeds and clinical reassessment 3

Common Pitfalls and How to Avoid Them

Pitfall #1: Delaying feeds unnecessarily

• Do not wait for bowel sounds or passage of flatus before starting feeds 3
• Do not delay for stable low-dose vasopressor use 3

Pitfall #2: Advancing too rapidly

• Avoid rapid administration—anecdotal reports document small bowel ischemia with high mortality from too-rapid advancement 4
• Respect the 5-7 day timeline to reach target 1, 4

Pitfall #3: Relying on auscultation for tube position

• Always obtain radiographic confirmation before first feed 2
• Tubes malpositioned in the lung have caused deaths 2

Pitfall #4: Overfeeding in the acute phase

• Providing full caloric requirements in days 1-3 may be harmful 2, 5
• Use a "defense" strategy early, transitioning to "offense" after day 4-7 5

Tube Maintenance

• Flush tube with 30-50 mL water after each medication or feeding 2
• Secure tube properly—dislodgement occurs in 40-80% of NG tubes without proper securement 2
• Consider nasal bridles for high-risk patients (reduces dislodgement from 36% to 10%) 2

When to Consider Alternatives

• If feeding needs exceed 4 weeks, consider percutaneous endoscopic gastrostomy (PEG) 2, 4
• In mechanically ventilated patients requiring prolonged nutrition (>14 days), early PEG may be preferred due to lower rates of ventilator-associated pneumonia 2
• If gastric feeding fails despite prokinetics, consider nasojejunal tube placement 1, 6

Special Populations

Post-Surgical Patients:

• In severely malnourished surgical patients, initiate feeding within 1-2 days post-operatively 2
• For major upper GI and pancreatic surgery in malnourished patients, consider nasojejunal tube or needle catheter jejunostomy placement at time of surgery 1

Pancreatitis:

• Use nasogastric route first; switch to nasojejunal only if digestive intolerance occurs 1
• Both polymeric and semi-elemental formulas are safe and well-tolerated 1