Total Parenteral Nutrition (TPN)
OVERVIEW
Total parental nutrition is the complete provision of nutrition intravenously, bypassing the GI tract.
INDICATIONS = unable to establish enteral feeding
General
- EN contraindicated (have low threshold to use perioperatively depending on nutritional state)
- EN fails to meet nutritional requirements
Specific
- prolonged bowel obstruction and ileus
- short bowel syndrome with severe malabsorption
- severe dysmotility
- high output intestinal fistulae
- anastomotic break down
- intolerance to EN
GENERAL
- ensure adequate central venous access (subclavian lines have lowest infection rates – aseptic insertion, 2% chlorhexidine in alcohol, permeable polyurethane dressings, antimicrobial catheters)
- dedicated lumen for TPN (daily infusion set changes)
- if requires TPN for > 2 months -> consider tunneled line
- assess why patient cannot be enterally fed -> this is known to be safer
- 12 hourly reassessment of whether patient can be enterally fed
- requires close liaising with dietician and pharmacy
ASSESSMENT OF NUTRITIONAL STATUS (CALORIC REQUIREMENTS)
- calculate Resting Energy Expenditure (using the Harris-Benedict equation)
REE (males) = 66.5 + (13.7 x body weight in kg) + (5.0 x height in cm) (6.8 x age in years)
REE (females) = 66.5 + (9.6 x body weight in kg) + (1.7 x height in cm) (4.7 x age in years)
- use ideal body weight
- resting energy expenditure in calories
- multiply this by a stress factor to allow for effects of disease (no exercise = 1.2, very heavy exercise BD = 1.9)
- more accurate to measure REE by indirect calorimetry
- most hospitalized patients require 25-30 kcal/kg/day
- mechanically ventilated are on the lower aspect of range
- burns and trauma patient may require 45 kcal/kg/day
- high protein hypocaloric nutrition preferred in obese patents (esp BMI >40)
NUTRITIONAL REQUIREMENTS
Protein
- utilisation of exogenous protein = 1.5g/kg/day
- other techniques:
-> non-protein calorie to nitrogen ratio (100-200kcal/g of nitrogen often used)
-> nitrogen balance = (protein intake (g) / 6.25) – (urinary nitrogen (g) + 4) -> 4 = empirical factor added to account for non-urinary nitrogen loss (faeces and sweat)
- crystalline solutions of L-amino acids (varying essential amino acids)
Carbohydrates
- daily requirement of glucose = 4-5g/kg/day in severely catabolic patients
Lipids
- requirements 1g/kg/day
- 1/3 of energy given as non-protein
- advantages: prevents fatty acid deficiency and provides more concentrated calories
- disadvantages: can cause pancreatitis, immunosuppression, overfeeding -> increase in CO2 production
- check lipids daily and check clearance of lipids
Minerals and Micronutrients
- Na+, K+, Ca2+, Mg2+, phosphate -> guided by serum plasma levels
- inorganic trace elements
- organic vitamins (thiamine, folic acid, fat soluble vitamins D, E, K, A, water soluble vitamins B and C)
H2O
- 25-40mL/kg/day (+ losses)
MONITOR FOR COMPLICATIONS
- catheter related sepsis
- catheter occlusion
- hyperglycaemia
- hypercholesterolaemia
- refeeding syndrome (Po43-, K+, Mg2+)
- abnormal LFTs
- trace elemental deficiency: > 2-4 weeks of poor nutrition
- copper: anaemia, neutropenia
- iodine: hypothyroidism
- chromium: glucose intolerance
- zinc: mental apathy, diarrhoea, rash
- selenium: cardiomyopathy
-> treatment: supplement, follow levels (serum, tissue, white cells)
PRESCRIPTION
- total energy: 25 kcal/kg/day
- protein: 1.5g/kg/day
- carbohydrate: 4g/kg/day
- lipids: 1g/kg/day
- H2O: 30mL/kg/day + other losses
- electrolytes
- organic vitamins
- inorganic trace elements
AN APPROACH
- exhaust all means of feeding enterally
- dietician involvement
- calculate requirements (caloric and nutritional)
- start slowly
- monitor for refeeding and complications
- frequent reassessment about whether patient can be fed enterally
VIDEO
References and Links
Journal articles
- Ziegler TR. Parenteral nutrition in the critically ill patient. N Engl J Med. 2009 Sep 10;361(11):1088-97. PMC3064749.
FOAM and web resources
- ICN — EXPLAINED: Parenteral Nutrition by Roger Harris (2014)
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
| INTENSIVE | RAGE | Resuscitology | SMACC
Hi,
This is the equation written at other sources ,
Please let me know why is yours different .
The Basal Energy Expenditure must be multiplied by activity and stress factors to calculate total caloric requirement.
BEE, kcal/day (male) = 66.5 + (13.75 × weight, kg) + (5.003 × height, cm) – (6.775 × age)
BEE, kcal/day (female) = 655.1 + (9.563 × weight, kg) + (1.850 × height, cm) – (4.676 × age)
What source indicates ideal body weight should be used?