Chapter 14: Overview of PN

Question 1

What are ILEs?

Answer 1

Lipid injectable emulsions

Question 2

What determines osmolarity of PN formulation?

Answer 2

Dextrose, AA, and electrolyte content

Question 3

How much osmolarity does dextrose contribute to PN formulations?

Answer 3

5 mOsm/g

Question 4

How much osmolarity does AA contribute to PN formulations?

Answer 4

10 mOsm/g

Question 5

How much osmolarity do electrolytes contribute to PN formulations?

Answer 5

1 mOsm/g of individual electrolyte additive

Question 6

What is the maximum osmolarity tolerated by a peripheral vein?

Answer 6

900 mOsm/g; anything higher requires CPN

Question 7

What does CPN stand for?

Answer 7

Central PN, aka TPN

Question 8

How is CPN safe?

Answer 8

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.

Question 9

How long can central venous access be maintained?

Answer 9

weeks to years

Question 10

(TRUE/FALSE)

Large fluid volumes must be administered with PPN to provide energy and protein doses comparable to those of CPN.

Answer 10

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.

Question 11

(TRUE/FALSE)

PPN is an undesirable option for patients with fluid restriction.

Answer 11

TRUE.

Concentrating the solution to meet their fluid requirements frequently results in a hyperosmolar solution that is not suitable for peripheral administration.

Question 12

(TRUE/FALSE)

PPN may be used in patients to provide partial or total nutrition support.

Answer 12

TRUE

Question 13

How long is PPN typically used for?

Answer 13

Short periods (up to 2 weeks) because patients’ tolerance is limited and because there are few suitable peripheral veins.

Question 14

(TRUE/FALSE)

PPN is generally indicated in malnourished patients requiring longer period of nutrition support.

Answer 14

FALSE.

PPN is NOT generally indicated… Only short periods (up to 2 weeks).

Question 15

What are the two criteria, that must be met, for PPN.

Answer 15

1. 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.

Question 16

(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.

Answer 16

TRUE

Question 17

Name some contraindications for PPN (6).

Answer 17

-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

Question 18

Define permissive underfeeding.

Answer 18

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.

Question 19

Define hypocaloric feeding.

Answer 19

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.

Question 20

Define supplemental feeding.

Answer 20

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.

Question 21

(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.

Answer 21

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

Question 22

**What are the indications for PN use:

Answer 22

**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.

Question 23

**What are the indications for CPN use:

Answer 23

**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

Question 24

**What is the recommendation for initiating PN in critically ill patients with normal nutrition risk or no malnutrition?

Answer 24

**Initiate PN when patient has been NPO/Inadequate intake x 7 days, with normal nutrition risk.

Question 25

**What is the recommendation for initiating PN when patients are malnourished or have high nutrition risk?

Answer 25

**PN is indicated when EN is not feasible.

Question 26

**What is the recommendation for initiating PN in other conditions that preclude the use of the GI tract?

Answer 26

**More than 7 to 10 days.

Question 27

(TRUE/FALSE)

Bowel rest is no necessary to achieve remission in Crohn’s disease.

Answer 27

TRUE.

Question 28

(TRUE/FALSE)

GI or bowel rest and PN no longer have a role in pancreatitis.

Answer 28

TRUE.

Recent reviews highlight the importance of maintaining GI integrity with EN as a means to avoid complications from pancreatitis and improve outcomes from the disease.

PN is unlikely to benefit patients with mild, acute or chronic relapsing pancreatitiswhen the conditions last for less than 1 week.

PN should be avoided unless EN is not feasible because of GI ileus, SBO, or the inability to properly place an enteral feeding tube.

Question 29

What are the recommendations for initiating PN when needed in treatment of pancreatitis?

Answer 29

PN energy administration should not exceed 25 to 35 kcal/kg/d and glucose be adequately maintained.

Consider glutamine supplementation to minimize the effect of being NPO on GI integrity.

Question 30

Define perioperative PN.

Answer 30

Reserved for patients with severe malnutrition at baseline, in whom the risk of surgery would outweight any benefit because of the high risk of postoperative complications.

Maximal benefit is derived in severly malnourished patients who receive PN for more than 7 to 10 days.

PN is still reserved for when other nutrition options (GI feeding) is not feasible.

Question 31

Define critical illness.

Answer 31

Characterized by a catabolic state that is generally the result of systemic inflammatory response to infectious or traumatic result.

Gut failure is common because of preferential blood supply to vital organs

Question 32

Define mesenteric ischemia.

Answer 32

It is poor circulation in the vessels supplying blood flow to your mesenteric organs: your stomach, liver, colon and intestine. With poor circulation, blockages can form and compromise the function of these organs.

Results from hemodynamic compromise and the use of vasopressors

Question 33

**ASPEN/SCCM Recommendation**

What are the recommendations for nutrition support in the ICU?

Answer 33

**ASPEN/SCCM Recommendation**

Recommend the enteral route as the preferred means of nutrition support in the critically ill. The greatest benefit derived in patients started on enteral feedings within 24 to 48 hours of ICU admission.

Question 34

**ASPEN Recommendation**

What are the recommendations for the provision of nutrition support in adult patients receiving anticancer therapy?

Answer 34

**ASPEN Recommendation**

Recommends a thorough assessment of the patient’s nutrition status and the use of PN ONLY in those who are malnourished and likely to be unable to ingest and absorb adequate nutrients for a period of 7 to 14 days.

EN always preferred with functional GI tract. Also, preferred in patients undergoing hematopoietic cell transplant because glycemic control is better during EN than PN.

Consider immune-enhancing EN formulas.

Question 35

What are the indications for home PN?

Answer 35

• Duration of PN is prolonged (more than 2 weeks)
• Medicare requires documentation that:
  
  • The patient’s GI tract is nonfunctional (“artificial gut”), AND
  • The condition is permanent (at least 90 days of therapy is needed), AND
  • Must have documented evidence of inability to tolerate EN (malabsorption, obstruction)