Chapter 14: Overview of PN Flashcards
What are ILEs?
Lipid injectable emulsions
What determines osmolarity of PN formulation?
Dextrose, AA, and electrolyte content
How much osmolarity does dextrose contribute to PN formulations?
5 mOsm/g
How much osmolarity does AA contribute to PN formulations?
10 mOsm/g
How much osmolarity do electrolytes contribute to PN formulations?
1 mOsm/g of individual electrolyte additive
What is the maximum osmolarity tolerated by a peripheral vein?
900 mOsm/g; anything higher requires CPN
What does CPN stand for?
Central PN, aka TPN
How is CPN safe?
The glucose, AA and electrolyte content provides a hyperosmolar formulation (1300 to 1800 mOsm/g) that must be delivered into a large-diameter vein, such as the superior vena cava adjacent to the right atrium. The rate of blood flow in these large veins rapidly dilutes the hypertonic parenteral feeding formulation to that of body fluids, maximizing the risk of complications associated with an IV infusion of hypertonic solutions.
How long can central venous access be maintained?
weeks to years
(TRUE/FALSE)
Large fluid volumes must be administered with PPN to provide energy and protein doses comparable to those of CPN.
TRUE.
Thus, making it an undesirable option for those with fluid restriction because concentrating the solution to meet their fluid requirements frequently results in a hyperosmolar solution that is NOT suitable for peripheral administration. Use CPN in this situation.
(TRUE/FALSE)
PPN is an undesirable option for patients with fluid restriction.
TRUE.
Concentrating the solution to meet their fluid requirements frequently results in a hyperosmolar solution that is not suitable for peripheral administration.
(TRUE/FALSE)
PPN may be used in patients to provide partial or total nutrition support.
TRUE
How long is PPN typically used for?
Short periods (up to 2 weeks) because patients’ tolerance is limited and because there are few suitable peripheral veins.
(TRUE/FALSE)
PPN is generally indicated in malnourished patients requiring longer period of nutrition support.
FALSE.
PPN is NOT generally indicated… Only short periods (up to 2 weeks).
What are the two criteria, that must be met, for PPN.
- Must have good peripheral venous access AND 2. Should be able to tolerate large volumes of fluid (2.5 to 3.0 L/day). Also, they should require at least 5 days but no more than 2 weeks of partial or total pN.
(T/F) ILE may be used to increase the energy density of the peripheral parenteral feeding formulation without increasing the osmolarity, and it has been reported to improve peripheral vein tolerance of PPN.
TRUE
Name some contraindications for PPN (6).
-Significant malnutrition -Severe metabolic stress -Large nutrient or electrolyte needs (potassium is a strong vascular irritant) -Fluid restriction -Need for prolonged PN (> 2 weeks) -Renal or liver compromise
Define permissive underfeeding.
A concept relevant to critically ill patients who do not tolerate nutrition, especially PN, well. This approach is intended to minimize complications of PN delivery by providing only 80% of estimated energy requirements until the patient’s condition improves.
Define hypocaloric feeding.
Used in both EN and PN therapy for obese patients to meet protein requirements but provide less energy than the estimated requirement. This approach is also designed to minimize the metabolic complications of PN while improving N balance. It is used for patients with a BMI greater than 30, unless weight loss is not intended. Note very little research is available for long-term (greater than 30 days) use of this approach.
Define supplemental feeding.
An approach designed to minimize the energy deficit that accumulates during periods of no nutrition or undernutrition. It is used in those circumstances where EN is insufficient to meet energy needs.
(TRUE/FALSE)
PN has been shown to benefit patients with moderate-to-severe malnutrition who have no or inadequate oral or EN for prolonged periods.
TRUE.
This is particularly relevant to the following populations: -Patients receiving perioperative support -Patients with acute exacerbations of Crohn’s disease, GI fistulas, or extreme short bowel syndrome -Critical care -Cancer patients
**What are the indications for PN use:
**ASPEN Recommendation:**
-PN may be appropriate for patients who are unable to meet nutrition requirements with EN. These patients are already or have the potential to become malnourished.
- PPN may be used in selected patients to provide partial or total nutrition support for up to 2 weeks when those patients cannot ingest or absorb oral or enteral tube-delivered nutrients, OR when CPN is not feasible.
- CPN support is necessary when PN is indicated for longer than 2 weeks, peripheral venous access is limited, nutrient needs are large, or FR is required, and the benefits of PN outweigh the risks.
**What are the indications for CPN use:
**ASPEN Recommendation:**
- The patient has failed the EN trial with appropriate tube placement (post-pyloric)
- EN is contraindicated or the GI tract has a severely diminished function because of the underlying disease or treatment. Specific applicable conditions are as follows:
- Paralytic ileus
- Mesenteric ischemia
- SBO
- GI fistula, except when enteral access may be placed posterior to the fistula or volume of output (less than 200 ml/day), support a trial of EN.
- The exact duration of starvation that can be tolerated without increased morbidity is unknown, as can occur in postoperative nutrition support. Expert opinion suggests that wound healing will be impaired if PN is not started within 5 to 10 days postoperatively for patients who cannot eat/tolerate EN.
- The patient’s clinical condition is considered in the decision to withhold or withdraw therapy. Conditions where nutrition support is poorly tolerated and should be withheld until the condition improves are:
- Severe hyperglycemia
- Azotemia (elevation in BUN > 100 mg/dL and [Cr] levels)
- Encephalopathy and Hyperosmolarity
- Severe fluid and electrolyte disturbances
**What is the recommendation for initiating PN in critically ill patients with normal nutrition risk or no malnutrition?
**Initiate PN when patient has been NPO/Inadequate intake x 7 days, with normal nutrition risk.