Academic Day Seminar – Total Parenteral and Enteral Nutrition

This was a really great session to have, and Jan did an absolutely terrific job going over this large topic and giving us practical take-away points on nutrition. This was definitely a very heavy topic and I’m glad I have a TPN rotation to try to apply the knowledge and concepts from this session.

I. The Basic Five for Enteral and Parenteral Nutrition:

  1. Equations
  2. Monitoring
  3. Tube/Access
  4. Delivery
  5. Formula

II. When you have the choice to decide between TPN and EN, EN is the 1st Choice!

  • Enteral Nutrition does not necessarily have lower risk than TPN
  • Risks of EN include:
    • Aspiration pneumonia (inability to protect airway)
    • Tube placement complications (e.g. perforation of GI tract)
    • Tube maintenance complications (esp with enteric tubes which migrate upwards and feeds to esophagus, potentially leading to aspiration)
    • GI intolerance
    • Inadequate intake (mean % received is usually 60% of what is prescribed)
    • Drug interactions (e.g. phentoin)
  • Risks of PN include:
    • Infectious complications (e.g. line infections)
      • Risk is now lower with better glucose control and stricter criteria to decide who gets PN
    • Catheter-related complications
    • Higher risk of refeeding syndrome (risk is still present with EN but with PN tend to be more aggressive with refeeding so risk is higher)
    • Liver dysfunction (PNALD = Parenteral Nutrition Associated Liver Disease)
    • Fluid/electrolyte/glucose imbalance (as increased tendency to be more aggressive with refeeding)
    • Gut mucosal atrophy (PN does not contain glutamine and GI is not being used)

✔ Enteral Nutrition

What are some barriers to providing EN?:

  • Developing procedures for safe EN practice
  • Thought that tube feeds cause diarrhea
  • CHIME: Constipation, History, Infection, Medications, Equipment


I. Energy

  • Factors that ↑ metabolic rate: lean body mass, physical activity and exercise, growth and development, being male, height (overall size), digestion)
  • Factors that ↓ metabolic rate: aging, fat mass (which is not metabolically active), starvation and dieting, sedentary living, being female (due to less muscle mass), sleep
  • % REE (= resting energy expenditure): as injury escalates (e.g. elective surgery → skeletal trauma → sepsis/peritonitis → major burns), the REE and metabolic response increases ..and when patients are in starvation, % REE decreases
  • Depends on the goal, which is usually: weight maintenance (vs. gain or loss)
  • Predictive equations: accuracy rate of 40-75% (compared to IC)
    E.g. Harris Benedict, Ratio Method
  • In ICU: Indirect calorimetry
  • What weight to use?:
    Adjusted body weight – highly debated in literature
    ADJ W = ((ABW-IBW)x25)+*IBW
    *Use BMI 25


  • Calculating protein needs:
    Most patients require 1.2-1.5g/kg/d of proteins, 20% total kcal


  • Multiple points of interface with water:
    1. Hydration, 2. Flushing EAD, 3. Dilution (medications, powdered formula)
  • Methods:
    • mostly done by age:
      20-55 yo: 35 mL/kg/day
      55-75 yo: 30 mL/kg/day
      >75 yo: 25 mL/kg/day
    • but this is just a starting point and will have to think of other IV fluids, current volume status, etc.
  • None of the formulas have been validated against a gold standard. No recommendations. Closely monitoring patients for optimal water intake regardless of which formula is chosen!


  • No tube = No nutrition (since no access)
  • No tube = No medication


Nasoenteric Tubes: Insertion site: Nose → GI tract

  • Irritant to nose…and risk of fistulas due to exposure of feeds
  • Nasogastric tube
  • Nasoduodenal tube (post-pylori)
  • Nasojejunal tube (post-pylori)

Enterostomy: Insertion site: GI tract → GI tract

  • Gastrostomy: Stomach → Stomach
  • Jejunostomy: Small bowel → Small bowel
  • Gastrojejunostomy: Stomach → Small bowel

Endoscopic Placement:

  • PEG: Percutaneous (through the skin) Endoscopic Gastrostomy
  • PEG-J: Percutaneous Endoscopic Gastro-jejunostomy
  • PEJ: Percutaneous Endoscopic Jejunostomy

Radiologic Placement:

  • PRG: Percutaneous radiologic gastrostomy
  • PRG-J: Percutaneous radiologic gastrojejunostomy
  • PRJ: Percutaneous radiologic jejunostomy

Radiologic vs. Endoscopic Placement: both equally successful (90-95%) with low mortality rates


  • anything less than French 12 should NOT be used for medications (d/t occlusion)
  • French 8 vs 12 = no difference in comfort for patients
  • MEDS ⇒ FRENCH 12
  • Internal diameter ~ External diameter


  • want larger diameters
  • need to allow tract to mature and form nice fistula tract (textbook typically states ~2 to 4 weeks but in reality it usually takes 4 weeks and might be longer for pts with impaired wound healing like diabetes)


Tube feeding routes:

  • Insertion site: Expected duration
    – if longer duration, should be away from nostril
    – enterostomy tubes: tend to be larger bore tubes
  • Terminus: Gastric function

Orogastric tubes: insertion site is mouth

  • Indication: trauma to nostril, sinus issues
  • more commonly seen in ICU (and some evidence suggesting decreased risk of VAP, but weak evidence)
  • if patients are conscious…may chew on the tube…but in ICU, use oroendotracheal tube which are larger and harder to chew

If < 4-6 weeks:

  • GASTRIC → NG (gastric) tube
  • If Gastric contraindicated (e.g. gastric stasis) → ND tube
  • CI: surgically altered gastric anatomy, delayed gastric emptying, GERD, increased aspiration risk, gastric outlet or duodenal obstruction, gastric or duodenal fistula

If 4-6 weeks:

  • GASTRIC → G (gastrostomy) tube
  • If gastric contraindicated → GJ tube or J tube (tube tip lies depending on whether the stomach is emptying)
  • Basal gastric acid secretion: 2.4-3L per 24 hrs
    • if patient has obstruction pre-pyloric, patient will be vomiting this you would want a tube tip to lie in J tube and a port in the stomach to decompress and get rid of acid


Delivery schedules: Important to know for dosing of medications!

  1. Continuous: run over 24 hours (start at lower rate and then titrated)
  2. Cyclic: a set rate that runs over less than 24 hours (usually a term used for nocturnal feeding…feed during night and disconnect during the day…may be because don’t want to be hooked up all day…or nocturnal feeds may be a supplement)
  3. Intermittent: larger volume of feeds delivered over shorter time (~1-2 hrs) (e.g. given at meal times)
  4. Bolus: similar to intermittent…taking larger volumes of feed delivered over a SHORTER time (~20 mins)

Most patients will be getting continuous delivery as possible fluid/electrolyte disturbances, gastric stasis and/or hemodynamic instability make more rapid administration potentially hazardous

Drug interactions:

  • Phenytoin
  • Ciprofloxacin

Dieticians don’t like post-pyloric tubes as cannot tolerate large volumes over a short time (e.g. diarrhea)

PICKING FORMULASEfficacy studies not required before products can be manufactured

  • Classifications: polymetric (everything is intact → fluid, fiber, protein), disease-specific, modular

When should a fluid restricted formula be used?

  • Renal dysfunction
  • RFS risk
  • Liver compromise
  • Cardiac compromise
  • Post-op fluid retention/redistribution

When should a fibre containing formula be used?

  • Fibre = good to help GI tract and lyte absorption…but not a lot of evidence
  • Insufficient data to support routine use of fiber in critically ill pts. Concerns re how fibre might be associated with harm in some pts (hemodynamically unstable, bowel ischemia risk, suppressed bowel motility)

When would a higher protein formula be used?

  • Depends on the patient’s injury


  • there are renal products (low protein) for CKD who are not on dialysis
  • for pulmonary compromise (e.g. someone intubated), high fat low carbohydrate = more CO2 is generated with carbohydrate → but evidence is weak
    – main thing is to not overfeed the patients
  • for hepatic products (e.g. encephalopathic patients) → have to show that correct fluid/lyte balance, metabolic stress, maximum therapy e.g. lactulose → if encephalopathic then may be a role for these products (removed from formulary at VGH)
  • for diabetic products: less carbohydrate and higher fibre with fat → this helps to slow gastric emptying…but no evidence supporting efficacy


Mnemonic: Good Monitoring Methods Improve Nutrition

  • GI: abdominal distension constipation, diarrhea (even for patients on PN since you want to know when we can use the gut, for example in patients who were put on PN d/t ileus)
  • Metabolic
  • Mechanical
  • Infection: tube site
  • Nutrition: mean % prescribed, ins and outs (e.g. feeds are held due to medications)
    • Do not look at albumin (since negative actue phase reactant and a measure of ILLNESS and not nutrition)
    • Do not look at weight (since measure of hydration)

DIARRHEAB5 JG Diarrhea 2017 final


Potential causes include:

  1. Poorly crushed meds
  2. Liquid meds with low pH – the pH of the formula is ~ 7…therefore, if a protein rich environment = causes precipitation of protein and occludes the tube…so liquid medications may not always be better (as well ingredients like sugars, preservatives, thickening agents can cause significant SEs)
  3. Viscious liquid medications
  4. Failure to flush tube before/between/after medications are given

Prevention includes:

  • Never add meds directly to feed or bag
  • If there is both a G and J port present, use the G port for meds
    (e.g. for dual lumen tubes – 1 lumen terminates in J port and 1 lumen terminates in the G tube for decompression)
    …if gastric stasis has resolved, and gastric emptying has improved = would want to use the G port since it is the larger bore and it is more physiologically better to access medications
  • If tube lumen < 12 Fr. Do not use for meds
  • Always flush medications


  • period of under nutrition, associated with fluid and electrolyte shifts and metabolic complications
  • Electrolyte replacement – consider comorbidities (e.g. renal failure pt)
  • For extreme risk at RLS (need to go slow with nutrition) to provide more time to replete electrolytes
  • Thiamine: water soluble (few stores in our body…can be depleted within 11-21 days)
    • deficiency: Wernicke’s encephalopathy (200-300mg daily)

Possible contributing factors of underfeeding:
1. Incorrect energy calculation
2. Too infrequent monitoring
3. Incorrect formula
4. Feed delivery interruptions (e.g. medication delivery)

If EN is to be held for meds, can consider:
1. PAD EN rate for time off pump
2. Consider switching to nocturnal feeds if drug dose during the day as BID or QID doses
3. Discuss with pharmacist re reduced drug dose frequency
4. Change to more energy dense formula

Other references:

✔ Total Parenteral Nutrition

  • KEY POINT: PRO 20%, CHO 50%, LIPID 30%
    • These % are generally safe as they will land you in between minimum and maximum dose
  • Average length: 6-10 days of TPN
  • Indications:
    • malnourished or at risk for malnutrition
    • contraindication to EN
    • patient cannot tolerate adequate EN
    • lacks sufficient bowel function to maintain or restore nutrition status due to GI dysfunction

Contraindications to EN:

  1. Severe hemodynamic instability
  2. Prolonged ileus, vomiting, diarrhea or persistent GI bleed
  3. Bowel obstruction
  4. Significant GI ischemia
  5. High-output fistula (if fistula that is gastric/small-bowel → can still enterically feed the patient by bypassing..but if too far down the GI tract where not enough surface area…may have to give it up)

Reasonable time frame for initiating PN when EN is not feasible in ADULTS:

  1. Initiate PN after 7 days for well-nourished, stable patients who have been unable to receive significant (>50% est requirements) oral or enteral nutrients
  2. Initiate PN within 3-5 days in those who are nutritionally at risk and unlikely to achieve desired oral intake with EN
  3. Initiate PN as soon as is feasible for patients with baseline moderate or severe malnutrition in whom oral intake or EN is not possible or sufficient
  4. Delay the initiation of PN in a patient with severe metabolic instability until the patient’s condition has improved


I. Protein:

  • Provide substrate to support organ structure/function; promote wound healing; support immunity
  • Energy value (same as enteral): 4kcal/g

II. Carbohydrate:

  • Source of energy
  • Composition: Dextrose monohydrate
  • Energy value: 3.4kcal/g
  • Min: 100g/d (for main organs  – e.g. CNS)
  • For peripheral access, higher mosmol/L = increased risk of thrombophlebitis
    For central access, osmolality is not an issue = can see D20W and D50W

III. Lipid injectable emulsion or ILE

  • Provides essential fatty acids and energy
  • Several types commercially available
    Differ in:
    1. Percent emulsion: 20%, 30%
    2. Type of oil: soybean, olive, other
  • Long chain omega acids thought to be immunosuppressive…but…as critical ill patients are malnourished…don’t worry too much about that

Electrolytes: requirements vary with: body weight, nutritional status, degree electrolyte depletion, organ function, ongoing electrolyte losses, acid/base balance, medications, disease process, carbohydrate composition

Nutrition – With refeeding syndrome, always start at LOWER doses (e.g. if patient needs 2000 cal → will give 1000 cal and then follow the PRO 20%, CHO 50%, LIPID 30%  = no issue even though carbohydrate drives refeeding syndrome more since will be at lower dose)

  • Most products are transitioning to not contain electrolytes
    (the values listed on the basic 5 facts are based on a healthy individual)
  • Managing short term electrolyte deficits by addition to the PN solution is not ideal
    • baseline/maintenance lytes (if needed) should be in TPN
      But…when in doubt, leave it out!
  • Electrolytes can be lost in NG suction!

Thiamine + Vit C: not unusual to add on additional thiamine and Vit C

  • FDA recommended that not enough vitamin C in products
  • Usually add on additional 100mg Vit C and 100-300mg Thiamine

Trace elements:

  • FH + VCH: Use Micro + 6 Concentrate
  • In short-term, standard is okay..but in longer term, concern about accumulation in trace elements especially in patients with altered liver dysfunction (but generally rare to not see the standard amounts of trace elements)
  • Iron not routinely added to PN solutions (as not stable and concern about infusion reactions)
  • PPN: Osmolarity < 900 mOsmol/L, limit 14 ds, have to rotate site
  • CPN: highly concentrated hypertonic solutions, may be used indefinitely

Compounding – PN product type:

  • Commerical pre-mixed: solution (lipid, CHO, PRO) and each macronutrient is kept in a separate entity…roll the bag and break membranes and get a 3 in 1 and with standard electrolytes for ~70kg
    – can add additional electrolytes and trace elements
  • Standard compounded
  • Custom compounded

!!Appropriate monitoring parameters shall include!!:

  • Fluid requirements
  • Serum electrolyte concentrations
  • Serum glucose concentrations
  • Hepatic function
  • Renal function
  • Serum triglycerides
  • Signs/ symptoms of access device complications

FYI: In pts with Anorexia Nervosa – albumin will be normal (as pt has adjusted)

  • if hit by truck = catecholamine response and for sick pts → albumin will be low


  • Potassium chloride and potassium acetate
  • Before adjusting the PN, what would you adjust?
    • If IV running…and then PN gets started and nobody has written TFI “Total Fluid In”… so if NS running where Cl: 154 mmol/L is going in → causing acid-base disorder

Impact of overfeeding with PN (since bypassing GI tract)  PNALD

  • Altered LFTs common
    • other factors can also affect liver dysfunction: sepsis, meds, etc.)
  • Lack of oral intake or EN: not stimulating gall bladder contraction to release bile
    • increase risk of stones
  • PNALD typically improves with the advancement of EN and discontinuation of PN
    • e.g. can we start trickling feeds to allow for stimulation of gall bladder and biliary tract
  • Some evidence that long-term soybean-based IVFE = increased risk with PNALD
    • Intralipid emulsion = starting to be taken off formulary (d/t liver concerns)
  • Some evidence that continuous PN is not physiologically normal and may be affecting liver function → may go with cyclical to give liver a break


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