Enteral Nutrition vs Parenteral Nutrition

OVERVIEW

• controversial issue
• at present best recommendations are to optimize oral/enteral nutrition, avoid forced starvation if at all possible, and judiciously use supplemental parenteral nutrition.
• data somewhat unclear on empirical outcomes
• feed the malnourished and plan to feed those that will be soon
• tendency to enterally feed first
• use simple goals based on patient size (25kcal/kg/day + 1.5g protein/kg/day)
• if EN delivery fails use TPN to complement or replace
• control glucose with insulin
• give glutamine

ENTERAL NUTRITION

• via NGT
• some risk may be minimised with PEG, post pyloric feeding or feeding jejunostomy

Advantages

• cheaper
• simpler
• fewer complications
• for efficient use of nutrients
• stimulates intestinal blood flow
• maintain GI mucosal barrier (prevents bacterial translocation and portal endotoxemia)
• reduced gut associated lymphoid system (GALT) -> becomes a source of activated cells and proinflammatory stimulants
• prevents disuse atrophy
• reduces septic complications compared with TPN
• avoids CVL complications
• avoids TPN induced immunosuppression (lipid load)
• improves healing
• improved weaning and recovery
• reduced muscle catabolism

Disadvantages

• independent risk factor for VAP (microaspiration, decreased with post-pyloric feeding)
• sinusitis (N/G)
• misplacement into trachea -> aspiration
• perforation of oesophagus, pharynx, stomach or bowel
• PEG use associated with high 30 day mortality (site infection -> abdominal wall infection, bowel obstruction)
• diarrhoea
• metabolic derangement: electrolytes, hyperglycaemia, re-feeding syndrome
• intolerance: vomiting, excessive aspirates (200-500mL), abdominal distension, constipation or diarrhoea

PARENTERAL NUTRITION

Advantages

• can be started early
• simple
• no delay in caloric intake
• does not rely of gastric/intestinal function
• less need for interruptions
• safe and less need for mechanical ventilation and better muscle mass if used early when relative CI to enteral nutrition (Doig et al 2013 ANZICS trial)

Disadvantages

• catheter related: sepsis, occlusion, insertion
• hyperglycaemia
• hypercholesterolaemia
  — use fat emulsions with low phospholipid to TG ratio, stop fat infusion, use IV heparin to increase plasma lipolytic activity, use insulin to increase lipase activity in adipose tissue
• refeeding syndrome
• abnormalities in LFTs
  — ?mechanism, may develop steatosis, cholecystitis
• hyperchloraemic metabolic acidosis
  — amino acids have a high Cl- content
• low bone mass ?unknown cause
• decreased GFR ?unknown cause

EVIDENCE

Summary

• last 15 years we’ve moved from TPN -> EN
• meta-analyses have produced conflicting results
• lower infective complications in enterally fed group, but no mortality change) – Gramlich, 2004, Nutrition
• clear reduction in mortality in patient fed by TPN – Simpson, 2005, Intensive Care Medicine
• timing of feeding seems to be as important as route
• data unclear

Doig G, et al. Early Parenteral Nutrition in Critically Ill Patients With Short-term Relative Contraindications to Early Enteral Nutrition: A Randomized Controlled Trial. JAMA 2013; epublished May 20th

• single-blinded MCRCT (n=1372)
• early parenteral nutrition (PN) in critically ill adults with relative contraindications to early enteral nutrition (EN)(n=686) with standard care (n=686)
• No difference in 60 day mortality
• No difference in ICU or hospital length of stay (LOS)
• Fewer days of mechanical ventilation, less muscle wasting and less fat loss

ACCEPT Trial (Martin, 2004, CMAJ)

• 14 hospital, cluster RCT
• when evidence based guideline for nutrition followed
  -> more nutrition was delivered more consistently.
• achieved by early introduction and more complete enteral nutrition without any decline in TPN alone or in supplementation

ANZICS Clinical Trial Group “The Effect of Evidence–Based Feeding Guidelines on Mortality of Critically Ill Adults: A Cluster Randomised Controlled Trial” JAMA 2008;300(23) 2731-2741

• cluster RCT
• 27 ICU’s
• Australia and NZ
• November 2003 -> May 2004
• n = 1118
• patients expected to stay in ICU > 2 days
  -> guidelines group – fed earlier, achieved caloric goals more often
  -> no difference in hospital discharge mortality, hospital length of stay or ICU length of stay

References and Links

LITFL

• CCC — Nutrition Literature Summaries

Journal articles

• ANZICS Clinical Trial Group “The Effect of Evidence–Based Feeding Guidelines on Mortality of Critically Ill Adults: A Cluster Randomised Controlled Trial” JAMA 2008;300(23) 2731-2741
• Doig G, et al. Early Parenteral Nutrition in Critically Ill Patients With Short-term Relative Contraindications to Early Enteral Nutrition: A Randomized Controlled Trial. JAMA 2013; epublished May 20th
• Heyland, DK. et al (2003) ‘Canadian Critical Care Practice Guidelines Committee. Canadian clinical practice guidelines for nutrition support in mechanically ventilated, critically ill patients.’ Journal of Parenteral Enteral Nutrition 27:355-373
• Heyland D, Muscedere J, Wischmeyer PE, Cook D, Jones G, Albert M, Elke G, Berger MM, Day AG; Canadian Critical Care Trials Group. A randomized trial of glutamine and antioxidants in critically ill patients. N Engl J Med. 2013 Apr 18;368(16):1489-97. PMID: 23594003.
• Ochoa Gautier. Early Nutrition in Critically Ill Patients: Feed Carefully and in Moderation. JAMA 2013; epublished May 20th