Meta Analysis
Parenteral vs. enteral nutrition in the critically ill patient: a meta-analysis of trials using the intention to treat principle
This review may be edited
Posted By: Gordon S. Doig
Posted Date: 6 Jan 2005
Title: Parenteral vs. enteral nutrition in the critically ill patient: a meta-analysis of trials using the intention to treat principle
Authors: Fiona Simpson and Gordon S. Doig
Reference: Intensive Care Medicine, Electronic Publication 9 Dec 2004
Link: Click here for a direct link to the paper. A password may be required for access to fulltext.
Abstract: OBJECTIVE: Controversy surrounds the use of parenteral nutrition in critical illness. Previous overviews used composite scales to identify high-quality trials, which may mask important differences in true methodological quality. Using a component-based approach this meta-analysis investigated the effect of trial quality on overall conclusions reached when standard enteral nutrition is compared to standard parenteral nutrition in critically ill patients.
METHODS: An extensive literature search was undertaken to identify all eligible trials. We retrieved 465 publications, and 11 qualified for inclusion. Nine trials presented complete follow-up, allowing the conduct of an intention to treat analysis.
RESULTS: Aggregation revealed a mortality benefit in favour of parenteral nutrition, with no heterogeneity. A priori specified subgroup analysis demonstrated the presence of a potentially important treatment-subgroup interaction between studies of parenteral vs. early enteral nutrition compared to parenteral vs. late enteral. Six trials with complete follow-up reported infectious complications. Infectious complications were increased with parenteral use. The I(2) measure of heterogeneity was 37.7%.
CONCLUSIONS: Intention to treat trials demonstrated reduced mortality associated with parenteral nutrition use. A priori subgroup analysis attributed this reduction to trials comparing parenteral to delayed enteral nutrition. Despite an association with increased infectious complications, a grade B+ evidence-based recommendation (level II trials, no heterogeneity) can be generated for parenteral nutrition use in patients in whom enteral nutrition cannot be initiated within 24 h of ICU admission or injury.
Are the Results Valid?
1. Did the overview address a focused clinical question?
Yes. The authors sought to compare the effects of standard parenteral nutrition to standard enteral nutrition in critically ill patients.
2. Were the criteria used to select articles for inclusion appropriate?
Yes. The authors provide a working definition of standard EN and standard PN and also provide a working definition of a critically ill patient population.
Trials with major methodological flaws (i.e. pseudo-randomised, excessive loss to follow-up) were not included.
3. Is it unlikely that important, relevant studies were missed?
Yes. The authors conducted an extensive Medline and EMBASE search, which was supplemented with a hand search of review paper reference lists. Experts and industry representatives were also contacted to contribute additional papers.
4. Was the validity of the included studies appraised?
Yes. A 'component approach' was used to determine the presence of three key methodological criteria: 1) presentation of an intention to treat (ITT) analysis, 2) maintenance of allocation concealment during randomisation and 3) appropriate use of blinding (e.g. participants, investigators, outcome adjudicators).
5. Were assessments of studies reproducible?
Unknown. The authors report that differences of interpretation were resolved by discussion but a formal measure of agreement was not reported.
6. Were the results similar from study to study?
There was no heterogeneity present when the primary outcome of mortality was aggregated.
There was moderate heterogeneity present when infectious complications were pooled.
What are the Results?
1. What are the overall results of the overview?
When ITT trials were considered, a statistically significant mortality benefit was evident in favour of PN (OR 0.51).
Based on an a priori specified subgroup analysis this overall benefit was attributable to trials that compared the use of PN to delayed EN (OR 0.29).
Although infectious complications were significantly increased (OR 1.66), due to authors of the individual trials pooling severe infections with sub-clinical infections,the clinical importance of these infectious complications could not be established.
2. How precise were the results?
For the primary outcome of mortality, ITT trials:
  • OR 0.51, 95% CI 0.270.97, p=0.04
    Sub-group analysis:
    PN vs. EN within 24 hours of ICU admission:
  • OR 1.07, 95% CI 0.392.95, p=0.89
    PN vs delayed (>24h) EN:
  • OR 0.29, 95% CI 0.120.70, p=0.006
    Infectious complications:
  • OR 1.66, 95% CI 1.092.51; p=0.02
  • Will the Results Help Me In Caring For My Patients?
    1. Can the results be applied to my patient care
    Yes. The patient populations and nutritional interventions included in the reviewed trials are adequately described. The applicability of the results to general ICU patients is support by the findings of a cluster randomised trial that evaluated the use of PN as would be recommended by this meta-analysis.
    2. Were all clinically important outcomes considered?
    The authors considered both mortality and infectious complications. Overall costs or ICU lenght of stay could not be abstracted from all papers.
    3. Are the benefits worth the harms and costs?
    In the face of a mortality benefit, the clinical importance of an increase in infectious complications is questionable. The upfront purchase costs of PN are likely offset by extra lives saved however a fully costed economic analysis is not available at this time.

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