Side Effects of Enteral Feeding  Though effective in delivering enough nutrition, feedings through nasogastric tubes can produce some side effects.
• You may suffer some throat irritation, nausea or vomiting.
• Some formulas, including cold or concentrated formulas, may cause diarrhea. The formula may have to be
  changed to lactose-free isotonic solutions at room temperature.
• Impaction and constipation can occasionally develop, possibly leading to an obstruction in the intestine.

Parenteral Nutrition  When neither oral nor enteral nutrition methods are appropriate, you can still get all the nutrients you need through a process called total parenteral nutrition (TPN), formerly called hyperalimentation . What it means is that you get all the proteins, carbohydrates, fats, vitamins and minerals you need intravenously.
    While you are receiving TPN, you may also eat solids and drink fluids, although TPN sometimes decreases the appetite.