Editing Nutrition (section)

== Parenteral Nutrition ==

Parenteral nutrition delivers nutrients intravenously, bypassing the gastrointestinal tract entirely. It is indicated when the gut is nonfunctional or inaccessible: short bowel syndrome, bowel obstruction, high-output enterocutaneous fistula, severe malabsorption, prolonged ileus, or intractable vomiting.

=== TPN Versus PPN ===

* '''Total parenteral nutrition''' is hypertonic, commonly greater than 10 percent dextrose and above roughly 900 mOsm/L, so it '''requires a central venous access device''' with the tip in the superior vena cava. Peripheral administration of TPN causes severe phlebitis and vein destruction.
* '''Peripheral parenteral nutrition''' uses lower dextrose concentrations and lower osmolarity for short-term partial support through a peripheral line.
* Solutions contain dextrose, crystalline amino acids, electrolytes, vitamins, and trace elements. Lipid emulsions supply essential fatty acids and calorie density and may be piggybacked or included in a three-in-one admixture.

=== Nursing Management of TPN ===

# '''Confirm central line tip placement by X-ray''' before the first infusion of a newly placed central catheter.
# '''Use a dedicated lumen.''' Do not infuse other medications, blood products, or draw blood from the TPN lumen unless policy explicitly permits it.
# '''Use an infusion pump and an in-line filter''' (typically 0.22 micron for lipid-free solutions and 1.2 micron for lipid-containing admixtures).
# '''Change the bag and tubing every 24 hours''' using strict aseptic technique. Refrigerate solution until use and remove it about 30 to 60 minutes before hanging.
# '''Inspect the bag''' before hanging. Discard if cloudy, discolored, or containing precipitate, and never add anything to the bag on the unit.
# '''Monitor capillary glucose every 4 to 6 hours''', at least initially. Hyperglycemia is the most common metabolic complication, and sliding-scale insulin is frequently required.
# '''Start slowly and taper off slowly.''' Initiate at a reduced rate and titrate up over 24 to 48 hours. '''Never abruptly discontinue TPN''', because the sustained endogenous insulin response causes rebound hypoglycemia. Taper the rate down, and if the bag runs out or the line fails, hang 10 percent dextrose in water at the same rate and notify the provider.
# '''Never "catch up"''' a TPN infusion that has fallen behind by increasing the rate, and never slow it abruptly. Both destabilize glucose.
# '''Monitor''' daily weight, strict intake and output, electrolytes, BUN and creatinine, liver function tests, triglycerides, and complete blood count.
# '''Assess the insertion site''' every shift for redness, drainage, tenderness, and swelling. TPN is an excellent bacterial growth medium and catheter-related bloodstream infection is the most common serious complication. A new fever in a patient on TPN is a catheter-related bloodstream infection until proven otherwise.

=== Key Complications ===

* '''Catheter-related bloodstream infection:''' fever, chills, elevated white blood cell count, site erythema. Obtain blood cultures from the catheter and a peripheral site, and notify the provider.
* '''Hyperglycemia''' from excessive dextrose delivery, and '''rebound hypoglycemia''' from abrupt cessation.
* '''Air embolism''' during tubing or cap changes. Signs are sudden dyspnea, chest pain, hypotension, and tachycardia. Immediately clamp the catheter, place the patient in '''left lateral Trendelenburg''' position, administer 100 percent oxygen, and call for help.
* '''Pneumothorax''' during subclavian insertion. Assess for sudden dyspnea, chest pain, and diminished unilateral breath sounds.
* '''Fluid overload''' from too-rapid infusion, particularly in heart failure and kidney disease.
* '''Hepatic complications''' including steatosis and cholestasis with prolonged use.

=== Refeeding Syndrome ===

Refeeding syndrome is a potentially fatal shift of fluid and electrolytes when nutrition is reintroduced to a severely malnourished patient. Insulin surges in response to the carbohydrate load and drives phosphate, potassium, and magnesium intracellularly.

* '''Hallmark finding: hypophosphatemia.''' Also hypokalemia, hypomagnesemia, thiamine depletion, and sodium and fluid retention.
* '''Consequences:''' cardiac dysrhythmias, heart failure, respiratory muscle failure, rhabdomyolysis, seizures, and death.
* '''At-risk patients:''' anorexia nervosa, chronic alcohol use disorder, prolonged fasting or nothing-by-mouth status, cancer cachexia, malabsorption, and the older adult with prolonged poor intake.
* '''Prevention:''' start feeding at low calorie loads and advance slowly over days, supplement thiamine before feeding begins, correct electrolytes before and during initiation, and monitor phosphorus, potassium, and magnesium closely along with cardiac rhythm and fluid status.