What are the possible causes of persistent vomiting in a patient receiving tube feeds?

Persistent Vomiting in Tube-Fed Patients: Causes and Management

The most common causes of persistent vomiting in tube-fed patients are gastrointestinal intolerance (occurring in 10-20% of patients), gastroesophageal reflux, tube malposition or displacement, delayed gastric emptying, and feeding-related factors such as excessive rate or volume. 1

Primary Gastrointestinal Causes

GI Intolerance and Delayed Gastric Emptying

• Nausea and vomiting occur in 10-20% of enterally fed patients, with abdominal bloating and cramps from delayed gastric emptying being particularly common. 1
• These symptoms represent the most frequent gastrointestinal complications across all tube feeding routes. 2
• Feeding rate, formula osmolality, and portion size directly influence tolerance and should be systematically evaluated. 2

Gastroesophageal Reflux

• Reflux occurs frequently with enteral tube feeding, especially when patients are fed in the supine position. 1
• The combination of gravitational backflow and impairment of the gastroesophageal sphincter (induced by pharyngeal stimulation and tube presence across the cardia) drives this complication. 1
• Reflux is particularly common in patients with impaired consciousness or poor gag reflexes, occurring in up to 30% of those with tracheostomies. 1

Mechanical Complications

Tube Malposition and Displacement

• Approximately 25% of nasogastric tubes fall out or are pulled out by patients soon after insertion, and tubes can be displaced by coughing or vomiting. 1
• A feeding tube with ports in the esophagus significantly increases aspiration risk and can cause vomiting. 3
• For gastrojejunal tubes specifically, retrograde migration of the jejunal extension back into the stomach occurs in 27-42% of cases, causing feeding intolerance with nausea, bloating, and vomiting. 4
• Displacement of a small bowel tube into the stomach of a patient with significantly slowed gastric motility creates particular problems. 3

Tube Obstruction

• Feeding tubes block easily, especially if not flushed with water before and after every feed or medication. 1
• Hyperosmolar drugs, crushed tablets, potassium, iron supplements, and sucralfate are particularly likely to cause blockage. 1
• Tube blockage can lead to feeding intolerance and vomiting when feeds cannot be properly delivered. 4

Metabolic and Infectious Causes

Refeeding Syndrome

• When commencing feeds in recently starved patients, refeeding syndrome can develop, causing multiple metabolic derangements that may present with gastrointestinal symptoms. 1
• This represents a serious metabolic complication requiring careful monitoring. 1

Infectious Contamination

• Enteral feed is an ideal culture medium; once contaminated, bacteria rapidly multiply and can cause gastrointestinal problems including vomiting. 1
• Stool samples must be checked whenever tube-fed patients develop new gastrointestinal symptoms. 1

Systematic Evaluation Algorithm

Immediate Assessment Steps

1. Verify tube position first - confirm placement radiographically if there is any doubt, as malpositioned tubes are a common and dangerous cause of feeding intolerance. 3, 5
2. Check gastric residual volumes - elevated residuals indicate delayed emptying or obstruction. 6
3. Assess patient positioning - patients should be at ≥30° angle during and for at least 30 minutes after feeding to reduce reflux and aspiration risk. 7, 4

Feeding-Related Factors to Modify

• Reduce feeding rate - rapid administration commonly causes intolerance. 2
• Evaluate formula osmolality - hyperosmolar formulas increase gastrointestinal symptoms. 1, 2
• Review medication administration - H2 blockers, proton pump inhibitors, antibiotics, and drugs containing sorbitol can cause gastrointestinal symptoms. 1
• Assess for tube blockage - attempt flushing with warm water; resistance indicates developing obstruction. 7

Special Considerations for GJ Tubes

• Stop feeding immediately and check both ports if a gastrojejunal tube is in place, as jejunal extension migration back to the stomach is extremely common (27-42% of cases) and defeats the purpose of post-pyloric feeding. 4
• Radiographic confirmation may be needed to verify jejunal tube position. 4
• The average functional duration of a jejunostomy extension is only 39 days, with most patients requiring multiple replacements (average 2.2 per patient). 4

Critical Pitfalls to Avoid

• Never assume the tube is correctly positioned without verification - blind placement complications continue to occur frequently, and malpositioned tubes are not routinely recorded in risk management databases. 3
• Do not force irrigation if resistance is encountered during flushing, as this may indicate obstruction requiring enzymatic intervention. 7
• Avoid carbonated drinks, pineapple juice, and sodium bicarbonate for flushing, as these degrade tube material. 7
• Do not overlook aspiration risk - most critically ill tube-fed patients receiving mechanical ventilation aspirate gastric contents at least once during early feeding, and those who aspirate frequently are 4 times more likely to develop pneumonia. 5