Meta Analysis
Canadian clinical practice guidelines for nutrition support in mechanically ventilated, critically ill adult patients
This review may be edited
Posted By: Pip Heighes
Posted Date: 18/11/08
Title: Canadian clinical practice guidelines for nutrition support in mechanically ventilated, critically ill adult patients
Authors: Heyland, DK., Dhaliwal, R., Drove, JW., Gramlich, L. & Dodek, P.
Reference: JPEN 2003; 27 (5); 355-373.
Link: Click here for a direct link to the paper. A password may be required for access to fulltext.
Abstract: OBJECTIVE: This study was conducted to develop evidence-based clinical practice guidelines for nutrition support (ie, enteral and parenteral nutrition) in mechanically ventilated critically ill adults.
OPTIONS: The following interventions were systematically reviewed for inclusion in the guidelines: enteral nutrition (EN) versus parenteral nutrition (PN), early versus late EN, dose of EN, composition of EN (protein, carbohydrates, lipids, immune-enhancing additives), strategies to optimize delivery of EN and minimize risks (ie, rate of advancement, checking residuals, use of bedside algorithms, motility agents, small bowel versus gastric feedings, elevation of the head of the bed, closed delivery systems, probiotics, bolus administration), enteral nutrition in combination with supplemental PN, use of PN versus standard care in patients with an intact gastrointestinal tract, dose of PN and composition of PN (protein, carbohydrates, IV lipids, additives, vitamins, trace elements, immune enhancing substances), and the use of intensive insulin therapy.
OUTCOMES: The outcomes considered were mortality (intensive care unit [ICU], hospital, and long-term), length of stay (ICU and hospital), quality of life, and specific complications.
EVIDENCE: We systematically searched MEDLINE and CINAHL (cumulative index to nursing and allied health), EMBASE, and the Cochrane Library for randomized controlled trials and meta-analyses of randomized controlled trials that evaluated any form of nutrition support in critically ill adults. We also searched reference lists and personal files, considering all articles published or unpublished available by August 2002. Each included study was critically appraised in duplicate using a standard scoring system.
VALUES: For each intervention, we considered the validity of the randomized trials or meta-analyses, the effect size and its associated confidence intervals, the homogeneity of trial results, safety, feasibility, and the economic consequences. The context for discussion was mechanically ventilated patients in Canadian ICUs.
BENEFITS, HARMS, AND COSTS: The major potential benefit from implementing these guidelines is improved clinical outcomes of critically ill patients (reduced mortality and ICU stay). Potential harms of implementing these guidelines include increased complications and costs related to the suggested interventions.
SUMMARIES OF EVIDENCE AND RECOMMENDATIONS: When considering nutrition support in critically ill patients, we strongly recommend that EN be used in preference to PN. We recommend the use of a standard, polymeric enteral formula that is initiated within 24 to 48 hours after admission to ICU, that patients be cared for in the semirecumbent position, and that arginine-containing enteral products not be used. Strategies to optimize delivery of EN (starting at the target rate, use of a feeding protocol using a higher threshold of gastric residuals volumes, use of motility agents, and use of small bowel feeding) and minimize the risks of EN (elevation of the head of the bed) should be considered. Use of products with fish oils, borage oils, and antioxidants should be considered for patients with acute respiratory distress syndrome. A glutamine-enriched formula should be considered for patients with severe burns and trauma. When initiating EN, we strongly recommend that PN not be used in combination with EN. When PN is used, we recommend that it be supplemented with glutamine, where available. Strategies that maximize the benefit and minimize the risks of PN (hypocaloric dose, withholding lipids, and the use of intensive insulin therapy to achieve tight glycemic control) should be considered. There are insufficient data to generate recommendations in the following areas: use of indirect calorimetry; optimal pH of EN; supplementation with trace elements, antioxidants, or fiber; optimal mix of fats and carbohydrates; use of closed feeding systems; continuous versus bolus feedings; use of probiotics; type of lipids; and mode of lipid delivery.
VALIDATION: This guideline was peer-reviewed and endorsed by official representatives of the Canadian Critical Care Society, Canadian Critical Care Trials Group, Dietitians of Canada, Canadian Association of Critical Care Nurses, and the Canadian Society for Clinical Nutrition. SPONSORS: This guideline is a joint venture of the Canadian Critical Care Society, the Canadian Critical Trials Group, the Canadian Society for Clinical Nutrition, and Dietitians of Canada. The Canadian Critical Care Society and the Institute of Nutrition, Metabolism, and Diabetes of the Canadian Institutes of Health Research provided funding for development of this guideline.
Are the Results Valid?
1. Did the overview address a focused clinical question?
The authors address 17 focused clinical questions associated with nutritional support in order to develop evidence based nutrition support guidelines for ICU practice.
This (my) appraisal will focus on question 2 "does early EN compared with delayed nutrient intake result in better outcomes in the critically ill adult patient?
The population of interest is critically ill adult patients (elective surgery excluded), intervention is early EN (started within 24 - 48hours), comparison is delayed nutrient intake (EN, PN or oral diet), outcomes assessed were mortality, infectious complications, length of stay, other complications (not specified).
2. Were the criteria used to select articles for inclusion appropriate?
The authors state they only selected RCT's or MA's of RCT's. Studies with only surrogate outcomes to be excluded.
On review of the trials included it is noted that despite the authors specifically stated intention to exclude pseudorandomised trials, there are pseudo-randomised trials included in some of the final MA's. For the question reviewed here re timing (Q2) there are no pseudorandomised trials included.
3. Is it unlikely that important, relevant studies were missed?
A comprehensive search was performed of 4 databases (Medline, EMBASE, CINAHL and Cochrane library). Suitable nutrition terms used without limitations. Personal files, reference lists and unpublished manuscripts also searched.
4. Was the validity of the included studies appraised?
All papers were assessed according to explicit criteria including nature of allocation, exclusions after randomisation, double blinding and assigned a level of classification (1 or 2) depending on results of this appraisal.
8 trials are included in the MA (for Q2), all are allocated level 2, indicating one or more of the following Level 1 criteria was not fulfilled - concealed randomisation, blinded outcome adjudication, ITT analysis performed.
5. Were assessments of studies reproducible?
The authors report a comprehensive search process. It is unclear what the process was for assessment of articles for inclusion. It is not stated how many authors participated in the selection process, or how they came to agree which articles to include in the final review at the guideline development conference.
6. Were the results similar from study to study?
For Q2 addressing timing test for heterogeneity was conducted using chi-square. p=0.67 which indicates non-significant result for heterogeneity
What are the Results?
1. What are the overall results of the overview?
For Q2 addressing timing, Early EN was associated with a trend towards a reduction in mortality
RR 0.52, 95% CI 0.25 - 1.08, p=0.08
Note the baseline mortality of the control group was 14.6%, with early EN reducing mortality to 6.3%.
2. How precise were the results?
See CI above
Will the Results Help Me In Caring For My Patients?
1. Can the results be applied to my patient care
This MA was conducted in critically ill patients. Baseline mortality of control group was 14.6% indicating the patient population is consistent with our ICU patients. A useful review to consider.
2. Were all clinically important outcomes considered?
Outcomes considered were consistent with other reviews in this topic area. No assessment of cost or quality of life.
3. Are the benefits worth the harms and costs?
If early EN does indeed reduce mortality, then yes. It is a fairly inexpensive intervention and this MA does not contain any evidence of harm

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