parenteral nutrition

Question 1

what are the characteristics of a parenteral lipid emulsion?

Answer 1

• Oil in water system   
• Similar to chylomicron
• Typically 0.2 ‐0.6m; 90% < 1m
• Thermodynamically unstable
• Shelf life:  typically 18‐24 months in room 
temperature

Question 2

what is the main content of a LE?

Answer 2

aq phase
triglicerides
emulsifier

Question 3

what makes up triglycerides?

Answer 3

• Oil core
• Calories and essential fatty acid (EFA) source (e.g.
linoleic acid)
• Long Chain TG (LCTG) e.g. Soybean oil, safflower oil
• Medium Chain TG (MCTG)
• Mixtures of LCTG and MCTG
• Structured lipid: esterification of Medium Chain FA &
Long Chain FA to form mixed TG by heat

Question 4

what are the properties of an emulsifier?

Answer 4

• Phospholipid from egg or soya lecithin
• Acyl chains, typically C16‐C18
• Phospholipid head group
• Charged stabilisation
• Ionisation behaviour
• Quantity depends on amount of oil
• E.g. Lipoid E100 or Ovothin 200, Lipoid® E80 and Ovothin® 180

Question 5

what are variables that affect a lipid emulsion?

Answer 5

Process parameters:
• Temperature
• Pressure
• Homogeniser passes

Formulation considerations:
• oil concentration
• emulsifier concentration 
• salt or electrolyte concentration
• pH 
• Drug concentration and properties

Question 6

what are the fate of lipid emulsions?

Answer 6

-dietary fat
peripheral tissue
liver parenchymal cells

Question 7

what nutritional support/ clinical nutrition is availible?

Answer 7

external nutrition- functional GI tract, good tolerance to external nutrition, sufficient enteral nutrient absorption

• sup feeding/ oral naturitional supplements
• yube feeding

parenteral nutrition: non-functional GI tract
poor tolerance ti enternal nutrition
total parenterak nutrition

Question 8

how would you define well nourished?

Answer 8

weight loss < 5% in 6 months
no/ small loss of percutaneous fat
appetite satisfactour
s-albumin>35g/l

Question 9

how would you estimate if someone was malnourished?

Answer 9

weight loss > 5% in 6 months
moderate loss of percutaneous fat
reduced intake food
s-albumin < 35g/l

Question 10

how would you estimate risk for malnutrition?

Answer 10

weight loss > 10% in 6 months
severe loss of percutaneous fat
severe loss of muscle mass
s- albumin < 30g.k , oedema

Question 11

what other reason can albumin be low?

Answer 11

due to inflamatory influence, burn injury after fluid resusitation

Question 12

what is PPN?

Answer 12

Peripheral parenteral nutrition’
• Supplement diet for patients who take food orally
• Peripheral intravenous catheter

Question 13

what are the two types of PPN?

Answer 13

– Lipid emulsion*

– Amino acid‐dextrose solution

Question 14

what is the osmolarity of a PPN? what is the ph?

Answer 14

• Osmolarity <900mosmo/L

* pH ~7.2

Question 15

give an example of a PPN?

Answer 15

• e.g. Nutriflex® Peri

Question 16

what is complete parenteral nutrition?

Answer 16

Extended period of intensive nutritional support

Question 17

give examples of TPN solutions?

Answer 17

– ↑[proteins and dextrose]
– Electrolytes, minerals, trace elements, insulin
– Admix with Lipid emulsion*
– Central venous catheter with infusion pump (subclavian or jugular )
– e.g. Nutriflex® Plus (all in one system)

Question 18

how do you compound and dispense parenteral nutrition?

Answer 18

• Review the appropriateness of PN prescription
• Risk assessment – Microbial contamination & other errors during compounding– Calculation or transcribing errors including unit conversion, tonicity issue
• Ready mix vs. Manual vs. Automated system
• Mixing sequence
• Base solutions (AA, dextrose and LE)
label

Question 19

how do you estimate tonicity?

Answer 19

final concentrations of dextrose or amino acid in PN admixture

Question 20

what is the purpose of amino acid supplements?

Answer 20

• Self buffered
• Standard and Special 
formulations (for 
renal or hepatic 
compromised or 
hypermetabolic
conditions & 
children]

Question 21

what is the mixing sequence for LE?

Answer 21

Particularly for 3 in 1 system with lipid emulsion
• High concentration of polyvalent ions, e.g. calcium
and phosphate supplements
• Vitamins added last

Question 22

what occurs when calcium phosphate occurs during mixing?

Answer 22

Precipitation occurs during mixing (related to order of
adding ingredients or on storage (slow crystallization)
• Adjust pH to favour formation of monobasic phosphate
salt
• Concentration of free calcium ions (depend on calcium &
AA sources, temperature etc.)

Question 23

what are the least stable ingredients in parenteral nutrition mixtures?

Answer 23

vitamins

usually added to pn immediately before infusion

Question 24

how are vitamins broken down in PN solutions?

Answer 24

• Breakdown by light and dissolved oxygen

Question 25

what vitamins are most sensitive to UV light?

Answer 25

retinol, vitamin A
– Use overwrap or administration at night or away from
daylight
– Use palmitate rather than acetate forms to avoid
sorption loss through infusion set

Question 26

how does the stability of water soluble vitamins differ?

Answer 26

• Vitamin C is most unstable of all the 
vitamins
• Conversion of Vitamin C to DHA via 
oxidation is a reversible reaction
• Oxalic acid can be toxic to body
• Sources of oxygen: dissolved air in 
the infusion bag; aeration of 
infusion during material transfers; 
residual air in compounded bag 
after sealing; air transmission 
through bag wall
• Oxidation is accelerated by trace 
elements, esp. copper, but is 
reduced by cysteine

Question 27

how do you define a parenteral nutrition?

Answer 27

• [amino acid] ≥ 2.5%
• pH ≥5.0
• [dextrose] ≥3.3%
• Add lipid emulsion last

Question 28

how do you prevent precipitation ?

Answer 28

– [amino acid] ≥ 2.5% plus cysteine
– pH 5.0 ‐6.0
– Infuse solution within 24 hours of preparation
– Use calcium gluconate instead of calcium chloride
– Avoid mixing Ca and P in close sequence during
preparation
– Total amount < 45 mEq/L