Exam 2 - PN Support

Question 1

What does PN stand for? What is it?

Answer 1

parenteral nutrition
- provision of nutrients directly into the bloodstream via an intravenous infusion when pt is unable to take nutrition orally or enterally

Question 2

Types of PN?

Answer 2

• CPN/TPN - delivery of nutrients via large central vein, cannot meet 100% of nutrient needs
• PPN - delivery of nutrients into a peripheral vein, cannot meet all nutrient needs (not ideal, for very very shor terms needs less than 2 weeks)

Question 2

What are some of the access sites for Parenteral nutrition?

Answer 2

Short term
- central venous catheter (CVC)
- peripherally inserted central catherter (PICC)

Long term
- tunneled
- implantable; completely under skin

Question 3

What are some basic compoenents to know when calculating PN nutrient needs?

Answer 3

• < 35 kcals/kg
• obese patients 11-14 kcal/kg bw or 60-70% of kcal requirement
• outcomes are better when patients aren’t overfed
• rule of thumb is recommended by ASPEN

Question 4

PN: Carbs

Answer 4

• in the form of dextrose monohydrate
• 5, 10, 50, or 70% solutions (50% is most common)
• Dextrose is 3.4 kcals/g
• maximum rate should not exceed 5 mg/kg/min

Ex: 50% solution has 50g dextrose in 100 ml solution

Question 5

PN: protein

Answer 5

• contains all essential AA, some nonessential
• concentrations between 3-20%
• maximum rate should be less than 2.5 g/kg/d
• 4 kcal/g protein

EX: 20% solution contains 20g protein in 100 ml

Question 6

PN: lipids

Answer 6

• 10% emulsions (soybean or safflower oil) = 1.1 kcal/ml; 20% emulsions = 2 kcal/ml
• Maximum 30% of kcals or 2.5 g/kg/24 hr
• Propofol – sedative agent; provides fat kcal (10%)

Question 7

PN: other components

Answer 7

• Electrolytes - Use of acetate or chloride forms affects acid-base balance
• Vitamins/mineral- usually as multiple infusion product
• Iron – not added to admixture, causes precipitation of lipid
• Fluid - Typical prescriptions 1.5 to 3 L/day

Question 8

What is the maximum glucose infusion rate and how is it calculated?

Answer 8

• Max: 5 mg/kg/minute
• (Grams dextrose x 1000 mg/g dextrose) ÷ (kg body weight) ÷ (1440 min/day)
• Example: 350g dextrose x 1000 = 350,000 mg dextrose; 350,000 mg dextrose ÷ 66kg = 5303; 5303mg/kg ÷ 1440 min/day = 3.7 mg D/kg/minute

Question 9

What are the effects of excess dextrose?

Answer 9

• Increased minute ventilation
• Increased CO2 production
• Increased RQ
• Increased O2 consumption
• Lipogenesis and liver problems – most commonly seen

Question 10

What are the steps to calculating a nutrition prescription?

Answer 10

1. Establish dosing wt/kcal requirement (using ASPEN recs)
2. Calculate protein goal
3. Determine lipid kcals (max 30%)
4. Distribute remaining kcal between CHO and protein
5. Determine electrolytes, vitamins, mineral
6. Determine fluid requirements
7. Calculate final prescription

Question 11

PN: administration

Answer 11

• Start slowly - 1/2 goal rate
• Stop slowly (reduce rate by half every 1 to 2 hrs or switch to dextrose IV)
• Cyclic give 12 to 18 hours per day – ½ rate 1st 1-2 hrs; ½ rate last 1-2 hrs
• When stopping, introduce enteral nutrition and then stop TPN/CPN – make sure they are meeting 75% of their needs before taking it off

Question 12

What is refeeding syndrome?

Answer 12

Refeeding syndrome caused by switch from energy from fat to energy from glucose
* Metabolic shift – glucose, K, PO3, Mg move from blood to tissues
* Hemodynamic - increased insulin = increased fluid, Na retention