Comprehensive notes for Clinical Nutrition 2 class. Topic: Parenteral nutrition. Based on class notes, teacher's slides and textbook readings. Content clearly summarized in bullet points but with enough details. Relevant charts and diagrams included. Ended up doing very well in the class.
What is PN?
o The infusion of drugs or nutrients intravenously
o Also called TPN (total parenteral nutrition) or CVN (ventral venous
nutrition)
o Formula contains dextrose, AAs, ILEs, electrolytes (K, Mg, P), vitamins
and trace elements (zinc, copper, manganese, selenium, chromium)
Osmolarity of PN
o Dextrose, AAs and electrolytes determine the formula’s osmolarity
o Dextrose: 5 mOsm/g
o AAs: 10 mOsm/g
o Electrolytes: 1mOsm/mEq
o ILE doesn’t affect osmolarity
Central parenteral nutrition
o Also called TPN (all nutrient reqt’s provided to pt. via a central vein)
o Formula delivered into a larger vein. Subclavian or jugular vein is
catheterized. 2-3 cm diameter, 7 cm long, 2L/min flow rate.
o Rate of blood flow in large veins quickly dilutes the hyperosmolar
formula to blood osmolarity levels
o Used for long term PN (more than 7-14 days). Can be maintained for a
long time (weeks to years)
o Requires surgery to be installed
o Provides complete nutrition in a reasonable fluid volume; can be
concentrated to provide sufficient energy and protein
o CPN formulas have high osmolarities (1300-1800 mOsm/L)
o Glucose content: 150 to 600 g/day
o Complications: sepsis, pneumothorax, embolism
Peripheral parenteral nutrition
o Lower osmolarity (600-900 mOsmo/L)
o Maximum osmolarity tolerated by a peripheral vein is 900 mOsm/L
o Dextrose: 150-300 g/day (5-10% of final concentration)
o Amino acids: 50-100 g/day (3% of final concentration)
o Provided with a large volume of fluids; cannot to concentrated to
maintain a lower osmolarity
o ILE can be used to increase energy density w/o increasing osmolarity
o Therefore, not to be used for fluid restricted patients.
o Can be used to provide partial or total nutrition support
o Used for short periods (aspen: up to 2 weeks; slides: 72-96 hours)
o May require site rotations to prevent phlebitis (at least q48-72 hrs)
, o Pts considered for PPN must:
Have good peripheral venous access AND
Have good tolerance for fluids (2.5-3 L/day)
o Contraindications: significant malnutrition, severe metabolic stress,
fluid restriction, large nutrient or electrolyte needs (K is a strong
vascular irritant), need for prolonged PN (>2weeks), renal or liver
compromise (unless well-managed)
New PN Concepts
o Permissive underfeeding: minimizing PN complications in critically ill
pts by providing only 80% of needs until pt improves
o Hypocaloric feeding: used in EN and PN with obese pts (BMI > 30) to
meet protein reqt’s but provide less energy than EER
o Supplemental PN: minimizing energy deficit that accumulates during
NPO periods or undernutrition. Used where EN is insufficient to meet
energy needs
Indications of PN
o Pt failed EN with appropriate tube placement
o Severe acute pancreatitis
o Inaccessible GI tract: paralytic ileus, mesenteric ischemia, small bowel
obstruction, GI fistulas that cannot be bypassed, short bowel
syndrome
o PN is indicated in cancer treatment that prevents adequate nutrtion
for more than 1 week
o PN is indicated in critically ill patients that are severely malnourished
if EN is not feasible
o PN is indicated in severely malnourished pts when a GI impairment
occurs
o PN is indicated in conditions that prevent the use of the GI tract for
more than 7-10 days
o For critically ill pts with normal nutrition risk or no malnutrition, PN
should be avoided for up to 7 days
o PN can only be used for pts who are hemodynamically stable and are
able to tolerate fluid volumes and CHO, AAs and ILE doses needed to
meet reqt’s
Conditions requiring caution when using PN
o Hyperglycemia
o Hypokalemia
o Azotemia
o Hyperosmolarity
o Hypernatremia
o Hypophosphatemia
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