Enteral and Parenteral Nutrition Support
Core concepts
Decide if, when, and how to feed. The gastrointestinal tract is preferred when functional: "if the gut works, use it." Enteral feeding preserves mucosal integrity, reduces bacterial translocation, and is cheaper and safer than parenteral routes.
Route selection follows duration and tolerance: nasoesophageal/nasogastric tubes for short-term (days) in anorectic but vomiting patients; esophagostomy for longer-term feeding with a functional stomach; gastrostomy (PEG) for long-term use and when the esophagus must be bypassed; jejunostomy when the stomach or proximal tract must be bypassed or the patient vomits despite gastric feeding.
Parenteral nutrition is reserved for patients that cannot use the gut (severe pancreatitis with intractable vomiting, prolonged ileus, massive bowel resection). Central lines allow hypertonic solutions; peripheral lines require dilute formulas.
Traps
- Refeeding syndrome: start at a fraction of RER (often one-third to one-half) and advance over 3-4 days, especially in chronically starved or very underweight patients. Monitor phosphorus, potassium, and magnesium.
- Do not overestimate energy needs in critically ill patients; illness factors are modest.
- Tube placement confirmation: radiograph after placement; check for aspiration risk and residual volume per protocol.
- Complications include diarrhea (often from too-fast advancement or hyperosmolar formula), aspiration, tube dislodgement, and metabolic derangements.
Worked example
A 4 kg cat with hepatic lipidosis: RER = 70 x 4^0.75 = 70 x 2.83 = 198 kcal/day. Start at one-third (66 kcal) and increase by ~25% every 24-48 hours while monitoring electrolytes.