TPN Flashcards
(29 cards)
what does parenteral nutrition mean?
Nutrition that bypasses the enteral, GIT system - ie feeding that does not involve the mouth, oesopagus, trachea, stomach, SI or LI - NONE of it it bypasses it!
What is parenteral nutrition ?
A chemical mixture of the nutritional substrates that we can get from our diet when we eat
What nutrients are typically included in TPN?
- electrolytes
- vitamins and minerals
- water
- triglycerides from fats
- amino acids from proteins
- glucose from carbs
What do we need to consider when preparing TPN?
sterility and chemical stability
TPN formulations can come as either “bespoke” or “off the shelf” - what does this mean?
Bespoke TPN - formulated for a specific patient with that patients specific needs in mind
Off the shelf TPN - pre - made formulations with standard concentrations of constituents - eg Kabiven
What are the conditions for preparation of TPN?
It must be made in an aseptic unit
How is TPN typically administered?
via a CVAD (central venous access device) - this is inserted/injected into the vena cava or the right atrium of the heart
what is the benefit of administering TPN via CVAD vs peripherally ie PICC)?
✓ we can admin a fairly high osmolality w/o any problems - bv the veins involved in CVAD are large (ie vena cava) - they have a strong flow and their volume is larger and so the TPN is diluted and thus the vein is less irritated
what are the risks of administering TPN peripherally ie via a PICC
❌ cant administer it to such high osmolality - thus the calorie content we can admin to the px is reduced
❌ If we admin TPN with high osmolality - risk thrombophlebitis and damage to the small veins in the arms and hands
Describe briefly how food is digested via the GIT, ie physiological enteral nutrition?
The primary function of the GIT is the digest and absorb nutrients and water from the diet.
1st food is mechanically digested in the mouth by chewing - then swallowed - eosophagus - stomach where further mechanical digestion takes place by churning of the food by the stomach
chemical digestion starts in the stomach where HCl breaks down the food —> chyme - passes via pylorus into duodenum
- gall bladder releases bile acids - emulsify fats
- pancrease - stimulates the release of pancreatic enzymes (amylase, triptase, lipase)
- chyme move into jej and ileum - maj nutrients absorbed into blood stream
- remainder of chyme/ passes via LI/ colon - H2O and some salts reabsorned - rest excreted via rectum as waste
What are the risks of associated with TPN?
-💉 insertion may lead to pneumothorax or haemorrhage (ie if we insert it too deep)
-🩸🦠 risk of septicaemia - via the introduction of new pathogens using the needle , despite sterile preparation
-🍫 hyperglycaemia - the majority of the composition of the TPN is glucose
- metabolic imbalance and fluid overload
Why is enteral feeding (ie via PEG) preferred rather than TPN?
It is the cheapest, safest and most physiologically normal method of nutrition
Give 3 examples of enteral feeding (ie via GIT)?
- NG
- NJ
- PEG
Why might enteral feeding be inappropriate, hence indicating TPN?
trauma or surgery in the small intestine or accessory organs that connect to it may lead to intestinal failure and prevent enteral feeding
what are the accessory organs near the SI?
liver, gall bladder, pancrease,
WHen does NICE recommend the use of TPN?
In patients with a non - functional, perforated or leaking, inaccessible GIT- these patients have intestinal failure
what is intestinal failure?
where a patients small and large intestines are non-functional, inaccessible, perforated or leaking GIT which prevents the absorption of water from the diet via the GIT
What is type 1 intestinal failure?
- acute + short term and usually a self limiting intestinal failure
- ie post operative ileus
What is type 2 intestinal failure?
a prolonged acute condition, often in metabolically unstable px requiring complex MDT care and PN over weeks or months
- ie a px in critical care
What is type 3 intestinal failure?
chronic condition ie crohns, UC, ileostomy etc, in metabolically stable px who require PN over months or years
what are some common indications for TPN (type 1 and 2)
- anastomotic leak following GI or hepato - biliary surgery (ie the surgeons have attempted to join up the GIT but its unsuccessful thus the nutrients are still not absorbed
- post operative paralytic ileus ( paralytic = SI not moving)
- intestinal obstruction
- fistula in the GIT
- “bowel rest” following complex GI surgery
- failed enteral feeding
what is an ileus?
A temporary lapse in the peristaltic movements of the small intestine
what are the two MAIN indications for TPN?
- Post operative paralytic ileus
- Pos surgical GIT complications such as anastomotic leaks
: ) TPN provides nutrition via an alternate route to the enteral feeding system and so if there are complications ie leaks with enteral feeding - tpn allows px nutrition to be maintained and allows for healing of the GIT
What are the 6 things we need to consider regarding the initiation of TPN?
- can the px be fed enterally - has it been tried - if not, why not?
- DO the benefits of PN outweigh the risks (ie septicaemia, metabolic imbalance, risks associated with insertion)
- Assess px risk of malnutrition and how long they have been without adequate oral or enteral nutrition - this helps us to decide how urgently they need TPN
- what is the px current weight/BMI
- what is the aim of the PN (ie maintain nutritional intake to allow healing of xyz, maintain nutritional intake until enteral nutrition can be established post - operatively)
- what is the exit strategy - what are the next steps if the underlying condition doesnt resolve
