TPN Learning Questions
Name: Hilary Rowe
Date: April 20, 2010
1. What are the contraindications for parenteral nutrition?
-Normal functioning GI tract
-If required for < 5 days and patient is not severely malnourished
-No venous access
-Diagnosis that does not need aggressive nutritional support
-When risks outweigh benefits
2. What is the range of basic maintenance requirement for protein in adults and
in what circumstances would you adjust.
-Basic maintenance requirements for protein in adults is 0.8-1g/kg/day in acute
care (typically 1.5-2.2 g/kg/day in critical care) based on stress and catabolism
-Would adjust protein if:
- Patient critically ill 1.5-2.2g/kg/day
- If catabolism 1.2-2g/kg/day (post-surgery, burn, dialysis)
- Severe catabolism 2-2.5g/kg/day
-Acute renal failure-1.5-1.6g/kg/day
-?Renal failure not yet dialyzed 0.8g/kg to avoid uremia
3. What is the maintenance requirement for energy in an adult (Total including
protein calories) and, of the non-protein calories, what percent is
carbohydrate and what percent is fat?
-Total energy: 25-30kcal/kg/day
-70-85% carbohydrates
-15-30% fat
4. What is the maintenance fluid requirement for adults per kg (per kg of actual
body weight)?
-30-40mL/kg
5. Identify potential sources of incompatibility and instability in TPN.
Instability
-order of mixing
-mixing technique
-pH
-Buffering capacity of the amino acid
-ratio of amino acids vs dextrose vs lipid
-concentration of cations
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Created by DBuna February 09; Updated by KRowat March 09, August 7, & Oct 30, 2009
TPN Learning Questions
-addition of medications
-age of lipid
-storage
6. Why are calcium and phosphate concentrations important in TPN?
-Calcium and phosphate concentrations depend on: pH, temp, aa solution,
concentration of aa/dextrose/length of storage
-The concentration of calcium and phosphate needs to be checked to rule out
emulsion destabilization and precipitation
7. Explain the concept of TPN “cracking”.
-An emulsion goes through a number of stages as it destabilizes, the last one
is “cracking” or “oiling out”. Normally an emulsion has particle sizes of 0.350.5 microns and is a uniform liquid. When “cracking” occurs the oil and water
completely separate and the oily layer floats to the top (looks like yellow
droplets or streaks). This TPN should not be used as it can be toxic to the
patient and is not a reversible phase of destabilization.
8. Why are divalent cations (e.g. Mg and Ca) concentrations important in 3-in-1
TPN?
-Cations have a greater valency and therefore, a greater attraction to the
negatively charged lipid droplets
-Divalent cations (Ca2+ & Mg2+) and trivalent cations (Zn3+ & Fe3+) are more
destabilizing than monovalent cations (Na+ & K+)
- Divalent cations bind “specifically” which can result in a positive charge
developing on the lipid droplet if the concentration is large enough
-This neutralizing or reversal of the negative charge on the lipid reduces the
negative electrostatic repulsion between the droplets = so lipid “fuses” or
“coalesces” into larger globules
-Results in destabilization and cracking
9. Compare and contrast 3-in-1 vs 2-in-1 TPN solutions in terms of contents and
when you would use these solutions. (IVFE = IV Fat Emulsion = lipid)
Solution
2-in-1
3-in-1
Core components
 Amino acid +
Dextrose in one bag
 Iipid separate bag

Amino acid,
dextrose and lipid
all in one bag
When to use
 Not enough lipid
to maintain
stability


Less
administration
handling,
convenient
Less chance of
administration
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Created by DBuna February 09; Updated by KRowat March 09, August 7, & Oct 30, 2009
TPN Learning Questions

error
Central
compounding
10. What is “Fat Overload Syndrome”?
-Symptoms of too much fat supplementation-lipid > 4g/kg/day:
hypertriglyceridemia, fever, hepatosplenomegaly, coagulopathy, organ
dysfunction
11. What sedative drug used in a critical care setting increases the risk of `Fat
Overload Syndrome’ and why?
-Propofol- is in a 10% lipid base and contains lipid calories 1.1kcal/mL and Vit
K
12. What micronutrients will affect the activity of warfarin and how do you adjust
for this?
–Vitamin K-give consistent amount each day and then monitor INR results to
determine if amount is too much
13. How much Vitamin K does lipid 20% emulsion contain?
-Intralipid 20% 67 mcg/dL
-Liposyn II 20% 22mcg/dL
-Liposyn III 20% 62 mcg/dL
-150mcg/day is found in 250ml of lipid
14. Is it necessary to supplement the Vit K in the TPN?
-Patients who are on TPN for < 1 week do not require supplementation but
those who are on TPN for weeks to months require 2-4mg/week or 510mg/week
15. List the potential complications of TPN.
-Hyperglycemia
-Re-feeding syndrome
-Cholestasis
-Fatty Liver
-GI atrophy
-Metabolic bone disease
-malnutrition or toxicity from too much or too little electrolytes, vitamins, minerals,
trace elements
16. When managing hyperglycemia in a TPN patient:
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Created by DBuna February 09; Updated by KRowat March 09, August 7, & Oct 30, 2009
TPN Learning Questions
a) What insulin do you add to the mixture, how much do you add and how
do you adjust?
-Regular insulin
-1unit of regular insulin / 10g of dextrose
-adjust by adding 70-100% of the sliding scale insulin used with previous
TPN
-if patients FBG is > 200mg/dL (11.1mmol/L) start with 1.5-2 units / 10g
dextrose
b) Should all TPN patients with hyperglycemia be given insulin?
-No, only patients who are diabetic
-If not diabetic check the amount of dextrose ordered and determine if the
patient is being overfed
17. What is your target range for blood glucose in a TPN patient?
-80-130mg/dL=4.44-7.22 mmol/L
18. Explain why “refeeding syndrome” occurs and outline the common signs and
symptoms. How would you help to reduce the adverse effects for a patient at
risk of refeeding syndrome?
-Refeeding syndrome is when there is a quick decline in K, Mg, PO4 &
vitamins and glucose intolerance occurs. This is caused by stimulation of
the pancreas and insulin secretion from introducing carbohydrates after
a period of malnourishment.
-When a patient is re-fed to fast their tissues are woken up and quickly
remove the glucose, electrolytes and vitamins from the blood so when
serum blood levels are measured the patient is very deficient. If the
tissue is woken up more slowly the equilibrium between tissue and blood
will be more balanced and the risk of water following the osmotic
gradient and edema occurring is reduced
-Clinical signs of edema from Na and fluid retention lead to cardiac and
respiratory failure. Other organs can be affected such as the kidneys and
GI tract and muscle complications and death can occur.
-Patients with anorexia, alcoholism, HIV, cancer, chronic starvation and
malabsorption issues are at greatest risk.
-In malnourished patients TPN should be started at low “refeeding”
calories of carbohydrates to reduce the chance of this syndrome.
-Patients can be given electrolytes before TPN or feeding is started
-Additional thiamine 100mg/day and folic acid 1mg/day should be added
to the multivitamin
19. Describe when/why you would consider enteral feeding over TPN.
-When the patient has a functioning GI tract-avoid atrophy
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Created by DBuna February 09; Updated by KRowat March 09, August 7, & Oct 30, 2009
TPN Learning Questions
-Expense
-Risk of infection with lines
-When >50% of calories are from enteral or PO intake TPN can be stopped
20.
Why is the following labwork drawn/values measured in TPN patients?
a) RBC folate and serum Vitamin B12
-To make sure patient is receiving enough of these vitamins to continue to
build red blood cells and reduce the risk of anemia
b) Alk Phos (alkaline phosphatase)
-elevated value is a sign of PN-associated cholestasis showing damage to
the biliary-tract
-Can also be elevated in bone disease
c) C-Reactive protein
?inflammation marker to show improvement
d) Pre-albumin
-found to be low in malnourished patients
e) INR
-liver function
-monitored in warfarin patients
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Created by DBuna February 09; Updated by KRowat March 09, August 7, & Oct 30, 2009