Clinical meaning
Total parenteral nutrition (TPN) delivers complete nutrition intravenously when the gastrointestinal tract cannot be used. TPN solutions contain dextrose (carbohydrate source), amino acids (protein source), lipid emulsions (fat source), electrolytes, vitamins, and trace elements. The high osmolarity of TPN (typically >900 mOsm/L) requires administration through a central venous access device to prevent phlebitis and vessel damage. Peripheral parenteral nutrition (PPN) can be used short-term but provides fewer calories due to osmolarity limitations. Hyperglycemia is the most common metabolic complication because of high dextrose concentration. The liver metabolizes TPN components, and hepatic steatosis can develop with prolonged use. Abrupt discontinuation can cause rebound hypoglycemia due to elevated endogenous insulin levels.
Exam relevance
Risk factors: - Non-functional GI tract (bowel obstruction, ileus, severe pancreatitis) - Short bowel syndrome with insufficient absorptive surface - High-output enterocutaneous fistula - Severe mucositis from chemotherapy preventing enteral intake - Prolonged postoperative ileus beyond 7 days