Lec 10- Parenteral Nutrition (PN)

Question 1

How to assess patients

Answer 1

• Malnutrition Universal Screening Tool (MUST)
  *

Question 2

Malnutrition and risk

Answer 2

• Malnutrition
  
  • BMI of less than 18.5 kg/m2
  • Unintentional weight loss greater than 10% within the last 3-6 months
  • BMI less than 20kg/m2 and unintentional weight loss greater than 5% within the last 3-6 months
• Risk of malnutrition
  
  • Have eaten little or nothing for more than 5 days and or are likely to eat little or nothing for the next 5 days or longer
  • Have a poor absorptive capacity and or have high increased nutritional needs from causes such as catabolism

Question 3

How can we feed patients

Answer 3

• Oral diet
• Oral diet and supplements
• Enteral feeding via a tube
• Parenterally with parenteral nutritional
• Or a combination of ways

Question 4

Nutrition team

Answer 4

• Doctors
• dietitians
• Nutrition nurses
• Pharmacist
• Biochemist
• Speech and language therapist- aid in regaining swallowing reflex

Question 5

What is parenteral nutrition

Answer 5

• Nutrition given IV that bypasses the normal process of ingestion and digestion in the GI tract
• Consists of
  
  • Protein
  • Carbs
  • Fat
  • Electrolytes
  • Vit and minerals/ trace elements (Vit A,D,E,K)
• Referred to as total parenteral nutrition (TPN) when it is the only nutrition the patient is receiving

Question 6

Protein

Answer 6

• Amino acids
• Essential amino acids are not synthesised by the body so need to be provided in nutrition
• Prescribed as grams of nitrogen
• Daily requirements 0.14g N/Kg/Day
  
  • Can vary depending on metabolic stress and catabolism
  • Higher requirements need to be taken into consideration

Question 7

Carbohydrate

Answer 7

• Glucose
• High calorie energy source
  
  • 25g glucose = 100 kcal
  • Requires exogenous or endogenous insulin
  • Primary non-protein energy source
• Usually 2g of glucose for every 1g lipid

Question 8

Lipid

Answer 8

• Need essential fatty acids
• Necessary for healthy cells
• Needed for fat-soluble vitamins
• Emulsion
  
  • Usually made from soya or fish oils
• 25g lipid = 225kcal

Question 9

Who needs PN

Answer 9

• Prolonged ileus
• GI fistula
• Anastomotic leak
• Post operatively where oral or enteral feeding is contraindicated or not possible for more than 4-5 day s
• Patients with malabsorption or who need complete bowel rest e.g. in
  
  • Crohns
  • UC
  • Severe pancreatitis
• Patients with severe burns
• Patients who are malnurished for other reasons (cancer)
• Patients with prolonged or chronic intestinal failure can receive long term PN

Question 10

NICE- who needs PN

Answer 10

• Malnurishedor at risk
• PLUS- inadequate or unsafe oral or enteral intake
  
  • Or
• A non-functioning, inaccessible or perforated GI tract

Question 11

When PN is inappropriate

Answer 11

• A functioning and accessible GI tract
• Patient who are not malnurished when treatment is for less then 5 days
• Risk outweigh benefit- High INR
• No access to administer

Question 12

Starting PN for a patient

Answer 12

• Need to assess the following
  
  • Weight (including loss) and height
  • Blood test
    
    • Mg, K, Na, PO4
    • Renal function
    • Liver function
  • Medical history
    
    • Surgical history
    • Recent nutritional intake
    • Pre-existing medical conditions- Diabetes, renal disease, liver disease

Question 13

Starting PN for a patient

Answer 13

• Calorie requirement s
  
  • 25-35kcal/Kg
  • 0.14g/Kg of N (but this can increase)
• Fluid requirements–
  
  • 25-30mL/kg
• Electrolytes
  
  • Sodium ~ 1mmol/k
  • Potassium ~ 1mmol/kg
  • Phosphate ~ 0.3 – 0.5 mmol/kg
  • Magnesium ~ 0.1 – 0.2 mmol/kg (usually around ~10mmol/day for an adult sufficient)
  • Calcium ~ 0.1 – 0.15mmol/kg
• Vitamins and trace minerals/elements

Question 14

Refeeding syndrome (feed someone too quickly after starvation)

Answer 14

• Metabolic abnormalities that occur upon refeeding malnourished person
• During a prolonged period of starvation:
• The liver decreases the rate of gluconeogenesis to conserve muscle and protein.
• Decreased insulin production and increased glucagon secretion.
• Body switches its energy source from glucose to ketone bodies.
• Glycogen stores are used up.
• BMR decreases.
• Several intracellular electrolytes and minerals become severely depleted.

Question 15

Refeeding syndrome

Answer 15

Question 16

Refeeding syndrome

Clinical features occur because of the funtional deficit of electrolytes and rapid change

Answer 16

• Metabolic consequences include:
  
  • Hypophosphataemia
  • Hypokalaemia
  • Hypomagnesaemia
  • Fluid balance abnormalities
• Pathophysiological consequences include:–
• Cardiac failure, respiratory failure, neuromuscular failure, renal failure, haematological failure, hepatic failure, GI system failure

Question 17

Refeeding syndrome- definition patients are at high risk of refeeding syndrome if

Answer 17

Question 18

Complications- refeeding syndrome

Answer 18

• When starting to feed a patient at risk of refeedingsyndrome:
  
  • Check electrolyte levels and replace if needed before commencing feed
  • Start feeding slowing (consider at least a 50% reduction)
  • Monitor patient:
  • Urea and electrolytes
  • Fluid balance
  • Temperature
  • Pulse and heart rate
  • Respiration rate
  • Blood pressure
  • Blood glucose

Question 19

Administration- central or peripheral

Answer 19

• Central venous access is usually the method of choice and is needed in most patients who receive PN (due to osmolarity of solution, irritate veins)
• It allows delivery of nutrients directly into the superior vena cava or the right atrium
• Peripheral access can be used the short term when using a solution with low osmolarity
• Careful monitoring for thrombophlebitis is needed.
• The line chosen should be dedicated to PN due to many incompatibilities with IV drugs

Question 20

Administration- choice of catheter

Answer 20

• Short term inpatient use:
  
  • A non-tunnelled central catheter (CVC
  • A peripherally inserted central catheter (PICC)
  • Peripheral catheter
• Medium-term use and home PN (HPN) <3months:
  
  • PICCs
  • Tunnelled catheters and ports
• Prolonged use and HPN >3months:
  
  • Tunnelled catheter
  • Totally implantable device

Question 21

PICC lines

Answer 21

Question 22

Totally implantable devices

Answer 22

Question 23

Standard PN bags

Answer 23

• Nutritional requirements vary from patient to patient depending on their size and disease state
• Calorie requirements for each individual patient need to be calculated
• Several companies manufacture a series of premade bags containing the pre-set amount of calories and electrolytes
• Stability can be longer (Upto 1 month)

Question 24

Advantages of Standard PN bags

Answer 24

• Convenient
  
  • Saves time
  • Makes pharmacy workload easier
• Safer
  
  • Fewer prescription error
  • Less contamination risk
• Cheaper
  
  • Saves money in production and resource cost

Question 25

Bespoke PN

Answer 25

• For patients whose requirements don’t fit in with standard bags, individual bags can be made.
• Some hospitals will manufacture on-site in aseptic suites and some with the order in from manufacturing companies.
• Useful for patients who have different electrolyte requirements, require fat-free PN or have different fluid requirements

Question 26

Biochemistry and monitoring

Why monitor

Answer 26

• To assess appropriateness to start PN
• To assess whether the regimen is suitable
• To prevent possible complications

Question 27

Biochemistry and monitoring

What do we monitor

Answer 27

• Weight
• Fluid balance
• U&E’s
• Liver function
• Glucose
• C-reactive protein (CRP)
• Albumin
• Catheter entry site

Question 28

Stability problems with PN

Answer 28

• Creaming
  
  • Accumulation of triglycerides particles at the top of the emulsion- embolisms
• Cracking
  
  • Separation of the oil and water components of the emulsion
  • Coalescence is the fusion of small triglyceride particles into larger particles (example 1)

Question 29

Stability problems with PN

Answer 29

• Aggregation
  
  • Clumping of triglyceride particles within the emulsion
• Other stability problems:
  
  • vitamins can undergo degradation in sunlight, also unstable with trace elements (Keep in the fridge and away from light)
  • calcium can bind with phosphorus forming an insoluble precipitate if at high concentrations

Question 30

Complications of PN

Answer 30

• Catheter related
  
  • Malposition- wrong line position
  • Pneumothorax
  • Air embolism
  • Occlusion
  • Catheter-related sepsis

Question 31

Complication of PN- metabolic

Answer 31

Question 32

Complication- Liver

Answer 32

• Hepatic cholestasis
  
  • Condition in which the flow of bile from the liver is blocked
  • PN causes intrahepatic cholestasis (i.e. it occurs inside the liver).
• Hepatic steatosis
  
  • Commonly known as ‘fatty liver’
  • Steatosis is the abnormal retention of lipids within a cell
  • Reversible condition

Question 33

Complications- Liver

Ways to overcome/reduce liver complications

Answer 33

• Cyclical PN
  
  • Infusing the bag over 12 to 20 hours to give a PN free period (give the liver a break)
• Fat-free bags
  
  • Bags containing no lipid given on a set number of days a week
• Oral/enteral feeding
  
  • If able, encouraging the patient to eat small amounts or have enteral feed running at a low rate.

Question 34

Home PN

Answer 34

• Indicated when the GI tract does not allow adequate absorption or transport of sufficient nutrients to maintain appropriate weight or growth and to support life.
• Indications are the same as inpatients but there are additional considerations:
  
  • Stable medical condition
  • Acceptance by patient & carers
  • The capability of patient & carers
  • Adequate support system
  • Adequate home environment

Question 35

Role of a PN pharmacist

Answer 35

• Work as part of the multidisciplinary team to ensure safe and appropriate provision of PN
• Assess PN prescriptions to ensure:
  
  • Clinically appropriate for the patient
  • Formulation is stable
• Formulate bespoke PN bags to a patient’s need
• Consider electrolyte content in relation to blood results
• Prescribe/liaise with prescriber for PN prescription
• Ensure PN is ordered/made in an aseptic lab and delivered towards for patients