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

Roger Harris on the physical properties of TPN solution (nothing to do with sex!):

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


CCC 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health, a Clinical Adjunct Associate Professor at Monash University, and the Chair of the Australian and New Zealand Intensive Care Society (ANZICS) Education Committee. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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