Parenteral nutrition Flashcards
What is the difference between acute and chronic malnutrition?
Acute:
Rapid development
e.g. in presence of stress, injury
Short lived
Should resolve with improvement of patients condition
Chronic:
Develops in disease states e.g. cancer, ibd, organ failure
requires longterm monitoring and therapy
When is IV TPN chosen over an enteral feeding tube?
When a patient has a non-functional or perforated gi tract
What are the possible reasons for TPN?
SHORT-TERM:
Post-surgery- nil by mouth for >7 days
obstruction in gut
severe shock or gut infection
malnourished or unable to eat
LONG-TERM:
Non-functioning gut
Not enough of gut to function e.g. large sections removed due to cancer
What are the components of TPN?
water
amino acids
glucose
lipids
vitamins
trace elements
electrolytes
How do you calculate maintenance fluid volume?
Maintenance fluid= 1500 ml + (20 ml x each kg of weight >20kg)
What factors can increase the TPN fluid (water) requirement?
Dehydration:
fever
acute anabolic state
high temp
low humidity
burns or wounds
blood loss
What factors can decrease the TPN fluid (water) requirement?
high humidity
blood transfusion
drugs that increase fluids
cardiac failure
renal failure
How are TPN prescribed in terms of protein?
Based on the amount of nitrogen (the form aa are in in TPN) e.g.
9g, 11g, 24g, or 18g
What is the usual dose of nitrogen for tpn bags?
0.2g nitrogen/kg/day
What is the usual dose of energy in tpn bags?
Most adults maintained on 25-30 non-protein kcal/kg/day
Where is the energy sourced from in tpn bags?
Dual energy source- Lipid and glucose
this minimises the risk of having too much of either
Glucose:
1g of anhydrous glucose = 4kcal
- should not be used as an energy source alone due to risk of hyperglycaemia, fatty infiltration of liver, excessive co2 production and 02 consumption
Lipid emulsions:
source of energy and essential fatty acids
Energy rich 0 10kcal per gram of oil
typically 2.5g lipid/kg/day
What are the advantages of using lipid emulsions for energy provision?
Large energy content in a small amount of fluid- good in fluid restricted patients
What factors affect the micronutrient requirements of patients tpn?
Baseline nutritional state on starting pn:
Diet history
duration and severity of inadequate nutritional intake
acute/chronic onset of illness
increaed loss of certain micronutrients
increased requirement
active growth e.g. child
increased metabolism
organ function
liver failure- copper, manganese clearance reduced
renal failure- clearance of aluminium, zind, nickel reduced
What are the electrolyted added adjusted in response to?
Daily blood tests monitoring electrolyte levels
What are types of TPN bags?
Standard bags- standardised bags that contain the average of what patients need and then are modified to the individual patient
Scratch bags- made entirely from scratch
What are the two types of administration of TPN?
PERIPHERAL:
Directly into a peripheral vein- 1st line option
indications:
short term duration
supplemental feeding
compromised access to central circulation
high risk of sepsis
Contra-inidcations:
inaccessible peripheral veins
high osmolarity of pn formulation e.g. if high calorie or nitrogen requirements
CENRAL:
inserted into jugular or subclavian vein- position has to be confirmed by x-ray
is invasive and costly
Indications:
long term feeding
peripheral route inaccessible
high tonicity formulations required
What is Refeeding syndrome?
Is a metabolic complication of PN
Occurs when infused nutrition exceed the tolerance of a previously malnourished patient.
- can cause morbidity or mortality
- Should start pn feeding slowly- e.g. 1 bag over 48 hours instead of 24 hours
- Add thiamine if at risk
How can refeeding syndrome be avoided?
- Start feeding slowly- Give the contents of one bag over 48 hours instead of 24 hours
- Give thiamine if at risk
