Parental Nutrition Flashcards
Indications for PN use
- Significant bowel dysfunction resulting in inability to achieve adequate enteral nutrition for > 7-10 days for adults (4-5 days for children & adolescents (2-18 years), or 1-3 days for infants/toddlers)
- Hypermetabolism with inability to meet needs via GI tract.
- Moderate-to-severe pancreatitis (or other GI diseases when patients present with acute adverse GI symptomology) requiring bowel rest > 7 days
- Bowel dysfunction
Contraindications to PN
- When the gut works, PN is contraindicated!!
- Previously well nourished adults where GI tract is expected to be functional in 7-10 days
- Prognosis does not warrant aggressive nutrition support (eg. palliation; note: PN can be part of palliation in children, not typically in adults)
- Vascular access is severely compromised and complications/risk associated with PN is greater than potential advantages.
Clinical conditions warranting cautious use of PN
- Severe hyperglycemia
- Severe end-stage renal failure
- Multi-organ system failure
- Severe metabolic acidosis or alkalosis
- Severe electrolyte disturbances (typically associated with severe metabolic acidosis/alkalosis).
Complications of PN
- Typically due to overfeeding and lack of GI stimulation
- Cholestatic liver disease (includes abnormal hepatic and biliary function) ± liver steatosis
- PN associated cholelithiasis (due to decreased secretion of cholecystokinin (CCK))
- Infection
What is Cholestasis?
reduction or stoppage of bile flow
Risk factors for cholestatic liver disease
- Prematurity of birth
- Duration of PN
- Infection
- Lack of enteral stimulation
- Bacterial overgrowth
- Overfeeding
What is cholelithiasis?
gallstones → hardened deposits of digestive fluid that can form in your gallbladder.
* The gallbladder is a small organ located just beneath the liver. The gallbladder holds a digestive fluid known as bile that is released into your small intestine.
Describe PIV
PIV = peripheral intravenous line (Peripheral Lines)
* usually last for 5-7 days; meant for short-term IV access
* Can only handle hypotonic or iso-osmolar solutions
* Mid-line: peripheral IV access last up to two weeks (not to be confused with a med-line (IV that delivers meds) which may be a CVL or PIV)
* Usually inserted in arm, feet or head (infants); can be elsewhere
mid-line versus med-line
- Mid-line: peripheral IV access lasting up to two weeks
- med-line: IV that delivers meds which may be a CVL or PIV
Describe CVL
CVL = central venous line (central lines)
* May last for months or years
* Can handle hypertonic solutions
* Multiple types
* Typically inserted into chest, arm or leg (eg femoral vein) typically bigger, central vein
Where do most chest catheters get inserted?
in the subclavian vein
Examples of CVL
- port-a-catheters
- chest catheters (eg. Hickman, Broviacs)
- PICC line
Describe the Broviacs & Hickman CVL
Types of central lines which differ in lumen diameter (Broviac is smaller lumen size)
* Catheter is placed directly into a central vein, usually in neck, upper chest, or groin and proceeds to position just above the heart (away from site where it enters the vein)
* May prevent bacteria from gaining access to central portion of catheter
* Are tunneled venous catheters
* Used for long term or recurring therapies
Describe portacatheters
- Access device: Central Line
- Located under the skin in the chest wall
- Often used when only need intermittent intravenous access (eg. patients on chemotherapy)
- Do not typically use for administration of PN
Device related complications
Infectious (most frequent); need to use aseptic techniques when handling IV lines
* Endogenous skin flora
* Contamination of catheter site
* Contamination of infusate (PN)
Non-infectious (Mechanical)
* Catheter occlusions
* Thrombosis
* Breakage
* Phlebitis (inflammation of vein near skin)
Peripheral vs Central PN
Peripheral PN
* PN is needed less than 2 weeks
* Patient not fluid restricted
* central PN not feasible
* Can meet BMR
Central PN
* PN is needed for more than 2 weeks
* Patient is fluid restricted
* Peripheral access is limited
* Total nutrient needs can be met
How do dextrose solutions for PN typically come?
In a PN pharmacy dextrose stock solutions are usuall yprovided as a D70W or 70% dextrose (this is a concentrated form of dextrose).
How are the dextrose stock solutions delivered to patients?
PN pharmacists dilute down the dextrose stock solutions to deliver lower concentrations to the patient.
* usually given to patient as a 10% or 20% (but can be a special, for example 17.5%)
How many calories does dextrose in PN provide?
Supplies the majority of non-protein calories and osmolality
* Provides 3.4 kcal/g
How is dextrose reported?
Typically reported in g/L concentrations on PN bag
* 10% solution = 100 g/L
* 20% solution = 200 g/L
* 30% solution = 300 g/L
30% not commonly used in AHS; but can be used substantially elsewhere.
How much dextrose can go into CVL vs. PIV?
% dextrose determined by type of IV line –solutions with > 12.5% dextrose cannot be infused via a PIV due to risk of phlebitis and decreased life span of line
* CVL=10-30%
* PIV = anything less than 12.5% w/v
What are the steps for dextrose concentration and kcal received?
- Multiply % dextrose given (D%W) by 10 to get the concentration in g/L
- Multiply the dextrose grams by the total amount of litres to determine the total amount of dextrose in the infuse (in grams)
- Multiply the total dextrose (g) by 3.4 kcal/g to get kcal amount for dextrose
- What is the concentration of D7.5W?
- If you wish to make 1.5 litres of a D7.5W how many kcal would you get??
- 7.5% x 10 = 75 gm in 1 L.
- 75 g dextrose x 1.5 L = 112.5 g dextrose
- In 112.5 g dextrose x 3.4 kcal/g = 382.5 kcal from dextrose.
What is the concentration of D5W and how many Kcal does it provide in 1500 mls.
- D5W provides 50 g dextrose in 1 litre or 50 g/L.
- In 1500 mls this provides 50 g dextrose X 1.5 L Litres or 75 g of dextrose.
- 75 gm of dextrose x 3.4 kcal/g = 255 kcal from dextrose
What might excess CHO in the PN lead to?
- Lipogenesis (conversion to fat) leading to liver damage
- Increased CO2 production (respiratory distress)
- Hyperglycemia (stress/insulin resistance, steroids, sepsis)
What does CHO contribute to which may be a problem?
Contributes to osmolality – watch in pts with PIV’s
* If in excess of the pancreas’ ability to secrete insulin get hyperglycemia; exceed renal threshold and get spilling of glucose into urine
What needs to be considered to prevent hyperglycemia due to high osmolality?
GIR - glucose infusion rate
Why is hyperglycemia a problem?
- insulin resistance
- iatrogenic diabetes
- renal and liver damage
How much glucose is okay in PN?
Adults: 3-5 mg/kg/min
* Typically should aim for < 4 mg/kg/min if possible (usually not more than 20-25 kcal/kg of CHO max). May give less if no problems with liver.
* When cycling of PN for Home PN; dextrose infusion rates may be higher; risk for metabolic syndrome/liver issues increases.
GIR calculation
What is the GIR for 18 yr old, weighing 49 kg, receiving 1753 ml of 200g/L dextrose solution PN running over 21 hrs? Are they on CVL or PIV?
5.7 mg/kg/ min and CVL since 200 g/L would be 20%
* This is too much!
What are the ways to impact the GIR?
- Change the dextrose concentration
- number of hours the dextrose is run over
- the volume of the dextrose that is delivered
What is the GIR for a 35 year old man, weighing 65 kg, receiving 1950 mls of a 17.5% w/v dextrose solution over 24 hours?
3.65 mg/kg/min
What lab variable are important to monitor for tolerance to IV GIR?
- Random blood sugars: should be 4.0-6.0 mmol/L
- Blood sugars over 10 mmol/L; exceed renal threshold; get spilling in urine (GLYCOSURIA) \ glucose in urine should typically be zero (if positive then the dextrose infusion rate is too high!)
- May have elevations in liver biochemical functions (aspartate amino transferase ( AST) and alanine aminotransferase (ALT)) due to steatosis! (only when in great excess)