Enteral Nutrition in ICU

Enteral Nutrition in ICU

• Every critically ill patient staying for more than 48 h in the ICU should be considered at risk for malnutrition.

Initiation of Nutrition Therapy in Critically Ill Patients (ESPEN 2023)

In non-intubated patients 

• Not reaching the energy target with an oral diet, oral nutritional supplements should be considered first and then EN.
• patients with dysphagia, texture-adapted food can be considered. If swallowing is proven unsafe, EN should be administered.
• patients with dysphagia and a very high aspiration risk, postpyloric EN or, if not possible, temporary PN during swallowing training with removed nasoenteral tube can be performed.

Oral Nutritional Supplements (ONS) are commercially prepared, nutrient-rich drinks, puddings, or powdersdesigned to provide extra calories, protein, vitamins, and minerals when a patient can eat by mouth but cannot meet nutritional requirements with a regular diet alone.

They are not a replacement for normal food; they supplement the patient’s oral intake.

Common Types

• High-protein (preferred for most ICU survivors and hospitalized patients).
• High-calorie (energy-dense; usually 1.5–2 kcal/mL).
• High-protein + high-calorie (most commonly used).

Typical Nutritional Content

A 200–250 mL bottle usually provides:

• 200–400 kcal
• 18–30 g protein
• Vitamins and trace elements

(Composition varies by product.)

Examples—Ensure®,Fresubin®,Resource®,Nutren®,Fortisip®

Obese patients

• An iso-caloric high protein diet can be administered to obese patients, preferentially guided by indirect calorimetry measurements and urinary nitrogen losses.
• Protein delivery should be guided by urinary nitrogen losses or lean body mass determination (using computerized tomography or other tools).
• If indirect calorimetry is not available, energy intake can be based on“adjusted body weight”If urinary nitrogen losses or lean body mass determination are not available, protein intake can be 1.3 g/kg“adjusted body weight”/d.

Early EN Indication

• Patients receiving extracorporeal membrane oxygenation (ECMO).
• Patients with traumatic brain injury (TBI).
• Patients with acute stroke (ischemic or hemorrhagic).
• Patients with spinal cord injury.
• Patients with severe acute pancreatitis.
• Patients after gastrointestinal surgery (once hemodynamically stable and the GI tract is functional).
• Patients after abdominal aortic surgery.
• Patients with abdominal trauma, after gastrointestinal continuity has been confirmed or restored.
• Patients receiving continuous neuromuscular blocking agents.
• Patients managed in the prone position (feeding can usually be continued safely with appropriate precautions).
• Patients with an open abdomen, if there is no bowel injury preventing feeding.

Delayed  Enteral Nutrition indications

• Uncontrolled shock with ongoing hemodynamic instability and inadequate tissue perfusion.
• Start low-dose EN only after shock is controlled with adequate fluids and vasopressors/inotropes, while closely monitoring for bowel ischemia.
• Enteral nutrition is contraindicated among patients with refractory shock or patients on high doses of vasopressors (e.g., greater than ~0.3-0.5 mcg/kg/min norepinephrine).
• Uncontrolled life-threatening hypoxemia, severe hypercapnia, or severe metabolic/respiratory acidosis.
• EN can be started once the patient has stable oxygenation and compensated or permissive hypercapnia/acidosis.
• Active upper gastrointestinal bleeding.
• Begin EN after bleeding has stopped and there is no evidence of rebleeding.
• Suspected or confirmed bowel (mesenteric) ischemia.
• This is an absolute contraindication to EN until the condition is treated.
• High-output intestinal fistula when feeding access distal to the fistula is not possible.
• In such cases, consider parenteral nutrition (PN).
• Abdominal compartment syndrome (ACS).
• Delay EN until abdominal perfusion and GI function improve.intra-abdominal hypertension give low dose EN
• if gastric aspirate volume is above 500ml/6h delay feed (ESPEN) BUT ASPEN—Tube feeds shouldn’t be held based on high gastric residual volumes unless there is additional evidence of feeding intolerance (e.g., distension, nausea, vomiting).If there is distention/tenderness, obtain an abdominal radiograph to exclude obstruction or ileus.Obtain a gastric residual volume.Either patient have Ileus or Gastroparesis so treat them accordingly.

Contraindications to enteral nutrition

• Obstruction.
• Severe ileus.
• Perforation.
• Mesenteric ischemia.
• Active, severe gastrointestinal bleeding.
• Abdominal compartment syndrome.
• High output fistula (with inability to access the gut beyond the fistula).
• Acute liver failure with uncontrolled hyperammonemia.
• High doses of vasopressors:greater than ~0.3-0.5 mcg/kg/min norepinephrine).

The following conditions are not contraindications to enteral nutrition:

• Absence of bowel sounds: This may simply indicate a lack of air in the intestines rather than dysfunction. The clinical significance of bowel sounds in decision-making has never been validated.(normal bowel sounds 5-30/min)
• Therapeutic paralysis: Paralytic agents only affect skeletal muscles, not smooth muscles like those in the intestines or pupils, meaning gut motility remains intact.
• Requirement to lie flat: While a semi-recumbent position is preferable to reduce aspiration risk, the evidence supporting this practice is weak, and feeding can still be initiated if the patient must remain supine.
• Use of low-moderate vasopressors: Concerns about intestinal ischemia during shock have not been substantiated. Enteral feeding may actually enhance gut perfusion and maintain intestinal integrity. Once fluid resuscitation is complete and the patient is stable on vasopressors, enteral nutrition can be cautiously initiated at low rates.
• Open abdomen: If no bowel injury is present, enteral feeding is recommended, even in patients with an open abdomen.
• Pancreatitis: Early enteral nutrition is beneficial in severe pancreatitis, similar to its role in other critically ill patients, as supported by current evidence.
• Procedures—There is little justification for stopping tube feeds before most procedures (e.g., interventional radiology), as proper sedation and analgesia minimize the risk of vomiting. Additionally, intubated patients have a protected airway, further reducing aspiration risk.
• Extubation—A common practice is to discontinue tube feeds at midnight if extubation is anticipated the next morning. However, in the absence of strong evidence, it may be preferable to continue feeding until a definite extubation decision is made. Before extubation, if the patient is receiving nasogastric or orogastric feeds, the stomach should be suctioned empty to minimize aspiration risk.
• Diarrhea-Tube feeding should NOT be held due to diarrhea(Treat the cause-evaluate for Cl.difficle,stop Magnesium based drug,Stop Hyperosmolar feed,Giver soluble fibre, stool cutter not helpful)

Methods Of Enteral feeding

Continuous vs. Bolus Feeding 

• Neither bolus nor continuous feeding has proven superiority for mortality, ICU length of stay, or infectious complications.
• Continuous feeding remains the standard initial strategy in most critically ill ICU patients because it is easier to tolerate.
• Bolus feeding may be considered in stable patients, particularly during recovery or rehabilitation, when a more physiological feeding pattern is desired.

Bolus Feeding 

1. Improved insulin sensitivity – Periodic fasting may enhance insulin sensitivity, thereby reducing insulin requirements
2. May increase superior mesenteric artery blood flow, mimicking normal meal physiology. 
3. Enhanced muscle protein synthesis – The pulsatile release of insulin and amino acids following meals stimulates muscle growth and repair.
4. Better achievement of nutritional targets – Even if a patient is NPO for part of the day, intermittent feeding allows for flexible meal rescheduling, making it easier to meet daily caloric and protein goals.
5. Higher success in reaching nutritional targets – RCTs have demonstrated that intermittent feeding is more effective than continuous feeding in achieving prescribed nutritional targets .

Implementing Bolus Feeding 

1. Determine Total Volume:
• Calculate the total daily volume of tube feeding needed.
• Divide it into 4-6 meals, with each meal typically 240-720 mL 

2. Optimize Meal Timing:

• Spacing meals during daylight hours may help maintain circadian rhythm and improve metabolic regulation.

3. Routes Suitable for Bolus Feeding

Continous Feeding(Preffered)

Despite being aphysiological(Delivers nutrition slowly over 16–24 hours.), continuous feeding has benefits in specific ICU scenarios:

• Hemodynamically unstable or critically ill patients (reduces metabolic stress).
• Patients with poor gastric emptying, severe gastroparesis, or high aspiration risk (gentler on the stomach).
• Early enteral nutrition in sepsis or shock (better tolerated at slow infusion rates).

Water Flushes

Purpose

• Prevent clogging
• Maintain hydration

Typical Flush Volumes

Medication Administration During Enteral Feeding

• Stop feed temporarily if needed
• Flush tube before and after medications
• Avoid crushing:
• Extended-release drugs
• Enteric-coated tablets

ENTERAL FEEDING ROUTES

│

├── 1. Oral Feeding

│      ├── Normal oral diet

│      └── Oral nutritional supplements

│

├── 2. Gastric Feeding

│      ├── Nasogastric tube (NGT)

│      ├── Orogastric tube (OGT)

│      ├── Percutaneous endoscopic gastrostomy (PEG)

│      └── Surgical gastrostomy

│

└── 3. Post-Pyloric Feeding

       ├── Nasoduodenal tube (NDT)

       ├── Nasojejunal tube (NJT)

       ├── PEG-J

       ├── Direct jejunostomy

       └── Surgical jejunostomy

NASOGASTRIC TUBE (NGT)

Salem Sump Tube

A Salem sump tube is a large-bore, double-lumen nasogastric (NG) tube primarily used for gastric decompression, aspiration, and lavage, not for routine enteral nutrition.

Structure

It has two lumens:

1. Main (Large) Lumen

• Used for:
• Gastric aspiration
• Decompression
• Gastric lavage
• Administration of medications (occasionally)

2. Vent (Blue Pigtail) Lumen

• Small blue tube (“pigtail”)
• Opens above the stomach
• Allows air to enter the stomach
• Prevents the tube from adhering to the gastric mucosa during suction
• Maintains continuous suction without damaging the stomach wall

Remember:

Blue pigtail = Air vent only
Never use it for feeding, flushing, or medication administration.

Principle

When continuous suction is applied through the main lumen:

• Negative pressure tends to pull the stomach wall against the tube.
• The vent lumen admits atmospheric air.
• This prevents mucosal injury and keeps suction effective.

PERCUTANEOUS ENDOSCOPIC GASTROSTOMY (PEG)

Major Indications

Neurological

• Stroke
• Parkinson disease
• MND/ALS
• Cerebral palsy

Head & neck cancer

Persistent dysphagia

Chronic neurological disease

Contraindications

Absolute

• Peritonitis
• Massive ascites
• Hemodynamic instability
• Gastric outlet obstruction
• Severe coagulopathy not corrected

Relative

• Morbid obesity
• Previous gastric surgery
• Portal hypertension
• Abdominal wall infection

Complications

Early—Bleeding—Peritonitis—Perforation

Late—Buried bumper syndrome,Tube blockage,Leakage,Granulation tissue,Infection.

Post-pyloric feeding 

• generally yields similar outcomes to gastric feeding in terms of mortality, ICU length of stay, and duration of mechanical ventilation. Gastric feeding is typically the first-line approach for intubated patients due to its ease of administration. 
• In patients with gastric feeding intolerance not solved with prokinetic agents, postpyloric feeding should be used-if postpyloric fedd also not tolerated then start PN.
• Can be placed at the bedside using electromagnetic guidance (CorTrak system)

ESPEN 2023 

Early postpyloric feeding (duodenal or jejunal tube) should be considered in critically ill patients with a high risk of aspiration.

Use postpyloric EN in patients with:

• High risk of aspiration pneumonia.
• Recurrent aspiration despite gastric feeding.
• Persistent gastric feeding intolerance despite appropriate management (e.g., prokinetics).

Patients at High Risk for Aspiration (ASPEN)

Patients with one or more of the following are at increased risk:

• Impaired airway protection (absent cough/gag reflex).
• Mechanical ventilation.
• Age >70 years.
• Reduced level of consciousness (sedation, coma).
• Neurological disorders (stroke, traumatic brain injury, neuromuscular disease).
• Gastroesophageal reflux (GERD).
• Supine positioning, especially prolonged.
• Poor oral hygiene.
• Frequent transport outside the ICU.
• Inadequate nurse-to-patient ratio, limiting close monitoring.
• Bolus/intermittent enteral feeding (higher aspiration risk than continuous feeding).

Classification of Enteral Feeds

ENTERAL FEEDS

│

├── 1. Blenderized (Kitchen/Hospital Prepared)

│      ├── Homemade blenderized diet

│      ├── Hospital kitchen churned feed

│      └── Commercial blenderized tube feed

│

├── 2. Commercial Sterile Formula

│      ├── Polymeric

│      ├── Oligomeric / Semi-elemental

│      ├── Elemental (Monomeric)

│      └── Disease-specific formulas

│

├── 3. Modular Formulas

│      ├── Protein modules

│      ├── Carbohydrate modules

│      ├── Fat modules

│      └── Fiber modules

│

└── 4. Specialized Immunonutrition

       ├── High-protein

       ├── Immune-enhancing

       ├── High omega-3

       ├── High EPA/DHA

       └── High MCT

1. BLENDERIZED (HOSPITAL-CHURNED OR HOMEMADE) FEED

• Prepared by blending ordinary cooked foods into a liquid consistency suitable for tube feeding.
• Typical ingredients:Rice,Dal,Milk,Egg,Chicken,Vegetables,Fruits
• Disadvantages—Non-sterile(Food poisoning),Nutrient inconsistency,High viscosity

ESPEN

Hospital-prepared blenderized feeds should not be routinely used in critically ill patients when commercial sterile formulas are available.

2. POLYMERIC FORMULA (STANDARD FORMULA)

• Contains nutrients in their intact (whole) form.
• Requires normal digestion. 
• ASPEN/ESPEN: Standard polymeric formulas are recommended as the first-line enteral formula for the majority of critically ill adults.

Composition

Typical Macronutrient Distribution

Contraindications

• Severe malabsorption
• Short bowel syndrome
• Pancreatic insufficiency (if unresponsive to enzyme therapy)
• High-output fistula with poor absorption

3. SEMI-ELEMENTAL (OLIGOMERIC) FORMULA

Also called

• Peptide Formula
• Hydrolyzed Formula
• Oligomeric Formula

Contains nutrients that are partially digested.

Composition

Indications

• Pancreatitis with malabsorption
• Crohn disease
• Short bowel syndrome
• Mild malabsorption
• Pancreatic insufficiency
• Persistent diarrhea thought to be related to maldigestion

Disadvantages

• Expensive
• Higher osmolality
• No consistent mortality benefit over polymeric formulas in unselected ICU patients

Guideline Recommendation

Not recommended routinely. Reserve for patients with documented or suspected malabsorption or intolerance to polymeric feeds.

4. ELEMENTAL (MONOMERIC) FORMULA

Contains nutrients requiring almost no digestion.

Composition

Indications

• Severe short bowel syndrome
• Severe malabsorption
• Extensive mucosal disease
• Rare cases of severe pancreatic insufficiency when other formulas fail

Disadvantages

Guideline Position

Reserved for selected patients; not recommended routinely in the ICU.

5. DISEASE-SPECIFIC FORMULAS

6. MODULAR FEEDS

Used to supplement, not replace, a complete formula.

ENERGY DENSITY OF COMMERCIAL FORMULAS

Fiber Content

The older practice of providing zero-fiber diets to all ICU patients is no longer supported. Modern ESPEN and ASPEN guidance favors selective use of soluble fiber in hemodynamically stable patients receiving enteral nutrition, while avoiding fiber in patients with gut hypoperfusion, bowel ischemia, severe ileus, or obstruction.

Monitoring of nutrition

Blood Glucose Monitoring

• Measure blood glucose:
• At ICU admission or when artificial nutrition (EN/PN) is started.
• Then at least every 4 hours for the first 48 hours.
• After stabilization, adjust monitoring frequency according to glycemic control and insulin requirements.

When to Start Insulin

• Start intravenous insulin therapy when blood glucose is persistently >150–180 mg/dL (8.3–10 mmol/L), according to the unit’s glucose control protocol.
• Avoid both severe hyperglycemia and hypoglycemia.

Electrolyte Monitoring During Nutrition Therapy

• Measure serum potassium, magnesium, and phosphate at least once daily during the first week after starting enteral nutrition (EN) or parenteral nutrition (PN).
• More frequent monitoring (e.g., every 6–12 hours) may be required in patients at high risk of refeeding syndrome, severe malnutrition, or with significant electrolyte abnormalities.

Management of Gastric Feeding Intolerance

First-line Prokinetic

• Intravenous erythromycin is the preferred first-line prokinetic for critically ill patients with gastric feeding intolerance.
• Dose: 100–250 mg IV every 8 hours (three times daily).

Important Points

• The prokinetic effect of erythromycin declines markedly after 72 hours (tachyphylaxis).
• Therefore, discontinue erythromycin after 3 days whenever possible.
• If prolonged therapy is needed, consider switching to or combining with metoclopramide.

Gastric Residual Volume (GRV) Monitoring

• GRV measurement may be useful during initiation and advancement of enteral nutrition (EN) to detect feeding intolerance.
• Routine GRV monitoring is not required once EN is well established and tolerated.

When to Delay Enteral Feeding

• Delay or temporarily hold EN if:
• GRV >500 mL over 6 hours, especially if associated with vomiting, regurgitation, or abdominal distension.
• Before stopping feeds, perform a clinical abdominal examination to exclude acute abdominal pathology (e.g., bowel ischemia, obstruction, perforation).

If GRV is High

• If there is no evidence of an acute abdominal complication:
• Start a prokinetic agent rather than immediately discontinuing EN.
• Continue close clinical monitoring.

Recommended Prokinetics

• Metoclopramide: 10 mg IV every 8 hours.
• Erythromycin: 3–7 mg/kg/day IV (or 100–250 mg IV every 8 hours).

High-Yield ICU Pearls

• Do not rely on GRV alone to diagnose feeding intolerance; always assess the overall clinical picture (vomiting, abdominal distension, pain, bowel function, rising lactate, hemodynamic status).
• Routine GRV monitoring is unnecessary in patients tolerating established EN.
• Persistent feeding intolerance despite prokinetics should prompt consideration of postpyloric feeding and evaluation for reversible causes (electrolyte abnormalities, opioid use, ileus, bowel ischemia).
• Erythromycin is more potent than metoclopramide for improving gastric emptying but is limited by rapid tachyphylaxis (≈72 hours).