Premixed formulas vary from those with standard ingredients to those with defined chemical composition tailored to a specific metabolic disorder. Although no formulas have been developed specifically for elderly people, special formulas are given for patients with kidney, liver or respiratory diseases. Rapid infusion of enteral formulas into the gastrointestinal tract can cause regurgitation, aspiration, vomiting, or diarrhea. Conversely, very slow infusion can result in inadequate nutrition and hydration. The patient's experience of tube feeding varies depending on whether conscious, unconscious, or confused.
Tubes can cause irritation of the nose and throat and difficulty swallowing.
For some, insertion of the tube can be frightening, and cause gaging. Others, learn to insert and remove the tubes themselves. TPN formulas are concentrated and can cause inflammation, occlusion, or clotting in small veins with low blood flow. In high-flow, central veins, the TPN formula is rapidly diluted. However, a constant and accurate infusion rate is critical.