Overview
Definition:
Enteral feeding, also known as tube feeding, is the administration of specialized liquid nutrition directly into the gastrointestinal tract via a tube
It is the preferred route of nutritional support when the GI tract is functional, aiming to maintain gut integrity, prevent bacterial translocation, and reduce complications compared to parenteral nutrition
This is crucial for surgical patients who may have increased nutritional demands and impaired oral intake.
Epidemiology:
Malnutrition affects a significant proportion of hospitalized surgical patients, with reported rates ranging from 20% to over 50% depending on the surgical specialty and patient population
Early initiation of enteral feeding is associated with improved outcomes, reduced infection rates, and shorter hospital stays, making its judicious use a cornerstone of surgical critical care.
Clinical Significance:
For surgical residents and DNB/NEET SS aspirants, understanding enteral feeding is paramount
Proper nutritional support accelerates wound healing, preserves muscle mass, enhances immune function, and reduces the risk of anastomotic leaks and surgical site infections
Inadequate or delayed nutrition can significantly impair recovery and lead to worse patient outcomes, impacting surgical performance metrics and patient safety.
Indications
Indications:
Enteral feeding is indicated in surgical patients who are unable to meet their nutritional requirements orally for more than 3-5 days, or who are at risk of malnutrition
This includes patients with altered consciousness (e.g., intubated patients, severe sepsis), significant head and neck trauma, esophageal or gastric surgery, severe pancreatitis, short bowel syndrome, inflammatory bowel disease flares, or generalized critical illness where oral intake is insufficient or impossible
It is also beneficial in hypermetabolic states like burns or major trauma.
Contraindications:
Absolute contraindications are rare but include complete bowel obstruction or ileus, severe intractable vomiting or diarrhea, significant malabsorption refractory to medical management, and hemodynamic instability where gut perfusion is compromised
Relative contraindications may include ischemic bowel disease where the risk of further compromise outweighs benefits, or when parenteral nutrition is more appropriate due to specific GI tract pathologies.
Access Routes
Nasogastric Nasoduodenal Tubes:
These are the most common and easily placed tubes, suitable for short-term feeding (up to 4-6 weeks)
Nasogastric tubes are inserted through the nose into the stomach, while nasoduodenal tubes bypass the stomach and enter the duodenum
They are ideal for patients with intact gag reflexes and normal gastric emptying.
Orogastric Tubes:
Similar to nasogastric tubes but inserted via the mouth
Primarily used in infants or when nasal passage is obstructed
Generally less comfortable and can interfere with oral hygiene.
Percutaneous Endoscopic Gastrostomy Peg:
A gastrostomy tube placed endoscopically directly into the stomach through the anterior abdominal wall
Suitable for long-term feeding (months to years) in patients requiring nutritional support beyond 4-6 weeks who have a functional GI tract but cannot tolerate nasogastric tubes
Requires intact gastric anatomy and no contraindications for endoscopy.
Surgical Gastrostomy Jejunostomy:
Gastrostomy tubes placed surgically, often during laparotomy for other indications
Jejunostomy tubes bypass the stomach entirely and are placed into the jejunum, often used in patients with gastroparesis, gastric outlet obstruction, or prior gastric surgery
These are also for long-term use.
Initiation And Advancement
Initiation Timing:
Enteral feeding should ideally be initiated within 24-48 hours of ICU admission or post-operatively for critically ill surgical patients if oral intake is not anticipated
For elective surgeries, it can be initiated pre-operatively to optimize nutritional status.
Initial Feed Rate:
Start with a low rate, typically 10-20 mL/hour, using a polymeric formula
This allows the gut to adapt to the feeding and minimizes the risk of feeding intolerance
Monitor for abdominal distension, pain, nausea, or vomiting.
Advancement Protocol:
Advance the feed rate by 10-20 mL/hour every 4-8 hours, provided the patient tolerates the current rate
The goal is to reach the full prescribed caloric and protein targets within 48-72 hours
Monitor bowel sounds, abdominal circumference, and gastric residual volumes (GRVs)
Current guidelines often suggest liberalizing GRV monitoring or using it only in specific situations of suspected intolerance.
Monitoring For Intolerance:
Key signs of intolerance include abdominal distension, tenderness, vomiting, diarrhea (more than 500-1000 mL per 24 hours, or >200 mL per 8-hour period, depending on protocol), high gastric residual volumes (e.g., >500 mL, though this threshold is debated and patient-specific), and absent bowel sounds
If intolerance occurs, consider reducing the feed rate, changing the formula, or assessing for underlying causes like ileus or medication side effects.
Nutritional Assessment And Formulas
Assessment Methods:
Nutritional assessment involves evaluating body mass index (BMI), unintentional weight loss, recent intake, muscle wasting, and subcutaneous fat loss
Subjective Global Assessment (SGA) is a validated clinical tool
Biochemical markers like albumin and prealbumin can be supportive but should be interpreted cautiously in the context of inflammation and fluid status.
Calorie And Protein Requirements:
Caloric needs in surgical patients typically range from 25-30 kcal/kg/day, but can be higher in hypermetabolic states (e.g., burns 30-35 kcal/kg/day)
Protein needs are elevated, often 1.2-2.0 g/kg/day, to support healing and immune function
Resting energy expenditure (REE) can be estimated using predictive equations (e.g., Harris-Benedict) or measured by indirect calorimetry, though the latter is not always practical.
Types Of Formulas:
Formulas can be polymeric (intact proteins, carbohydrates, and fats, suitable for most patients), elemental (amino acids, simple carbohydrates, and medium-chain triglycerides for malabsorption), semi-elemental (short peptides, increased MCTs for impaired digestion), or disease-specific (e.g., high protein, immune-modulating with arginine, glutamine, omega-3 fatty acids for critically ill or septic patients)
Fiber content and osmolality are also important considerations.
Complications
Gastrointestinal Complications:
Common complications include diarrhea, constipation, nausea, vomiting, abdominal distension, and high gastric residual volumes, often indicative of feeding intolerance or underlying ileus
Malabsorption can occur with certain formulas or in patients with compromised gut function.
Mechanical Complications:
Tube displacement, dislodgement, or occlusion are common
Tube-related skin breakdown, sinusitis (with nasogastric tubes), and tracheoesophageal fistula (rare, with prolonged uncuffed tubes in intubated patients) can also occur.
Metabolic Complications:
Refeeding syndrome is a potentially life-threatening complication, characterized by fluid and electrolyte shifts when refeeding malnourished patients too rapidly
Hypophosphatemia, hypokalemia, and hypomagnesemia are key features
Electrolyte imbalances, hyperglycemia, dehydration, and aspiration pneumonia are also risks.
Key Points
Exam Focus:
Understand the indications, contraindications, and preferred routes of enteral access
DNB/NEET SS questions often test knowledge of initiating feeds, advancement protocols, monitoring for intolerance, and managing common complications like diarrhea and refeeding syndrome
Differentiate between polymeric, elemental, and specialized formulas and their uses.
Clinical Pearls:
Always start feeds slowly and advance gradually
Assess gut tolerance subjectively and objectively, not solely relying on arbitrary GRV cutoffs unless specific patient factors warrant it
Consider prokinetic agents if feeding intolerance persists and no mechanical obstruction is present
Document fluid balance and electrolyte status diligently, especially during rapid advancement or in critically ill patients
Collaborate with dietitians for optimal formula selection and titration.
Common Mistakes:
Starting feeds too aggressively, leading to intolerance
Over-reliance on gastric residual volumes as the sole indicator of intolerance
Delaying initiation of enteral feeding in indicated patients
Failing to adequately monitor for and manage complications like diarrhea or refeeding syndrome
Not considering alternative feeding routes when initial methods fail.