When do you use tpn?

Last resort: Typically TPN is used as a last resort for patients who can get nuturion by no other means. Because there are some risks inherent to this method, doctors typically will only use this when they have no other good alternatives.

Gut doesn't work: Tpn is used when it's not safe to use the GI tract (bowel obstruction, for instance) or when the GI tract isn't functioning properly (e.g. Short-bowel syndrome, high-output fistula, malabsorption problem, etc.).