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CI: Best Method to Estimate RMR (2010)

Citation:

MacDonald A, Hildebrandt L.  Comparison of formulaic equations to determine energy expenditure in the critically ill patient.  Nutrition 2003;19(3):233-9. 

PubMed ID: 12620525
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To compare 5 previously published predictive equations and nomograms of kcals/kg body weight used to calculate EE in the critically ill with MEE determined by indirect calorimetry to determine which equations most accurately estimated an individual's energy needs.
Inclusion Criteria:

Critically ill patients, on mechanical ventilation, and most receiving parenteral and/or enteral nutrition support.  Inclusion criteria for indirect calorimetry measurements included:

  • mechanical ventilation with a fraction of inspired oxygen smaller than 80% without an air leak
  • absence of chest tubes with air leaks
  • no hemo or continuous dialysis during the measurement period
Exclusion Criteria:

Patients were excluded from the study if they were:

  • pregnant (n=1)
  • BMI > 30 (n=44)
  • had a preexisting amputation (n=1)
  • expired (n=1)
  • fraction of inspired oxygen requirements increased above 80% (n=2)
  • IC measures that were completed within 12 hours (n=5)
  • second or third measures on the same patient (n=7)
Description of Study Protocol:

Recruitment

139 clinical records of patients undergoing 24-hour continuous indirect calorimetry admitted to an adult ICU from June 1996 to April 2000.

Design

Cross-Sectional Study - Retrospective review.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

RMR measured using indirect calorimetry and compared to estimates from equations.

Statistical Analysis

Descriptive statistics were obtained for each variable.  Differences between equations were analyzed with Student's t test for paired samples.  Measures of relationships were calculated by the Pearson's and Spearman's correlation tests.  Simple and multiple regressions were used to relate clinically independent variables to the MEE.  Significance set at P < 0.05.

Data Collection Summary:

Timing of Measurements

Demographic info for variables taken from medical chart.

Dependent Variables

  • RMR determined by continuous 24-hour indirect calorimetry with Puritan Bennett 7250 open circuit metabolic monitor, calibrated at the beginning of each measurement and self-calibrated throughout measurement
  • RMR estimated with Harris-Benedict equation
  • RMR estimated with Frankenfield equation
  • RMR estimated with Swinamer equation
  • RMR estimated with Penn State equation
  • RMR estimated with Ireton-Jones equations

Independent Variables

  • Sex, age, height, weight
  • Reference weight using Hamwi equation, adjusted weight, body surface area and BMI were calculated
  • Diagnoses, APACHE II and Simplified Acute Physiology Scores were calculated

Control Variables

 

Description of Actual Data Sample:

Initial N: 139 clinical records of patients reviewed, only 76 subjects met all inclusion and exclusion criteria.

Attrition (final N):  76 subjects, 39 male, 37 female.  See exclusion criteria.

Age:  mean 59 +/- 16.7 years

Ethnicity:  not mentioned

Other relevant demographics:  mean APACHE II score 12.6 +/- 7.5

Anthropometrics:

Location:  Michigan 

 

Summary of Results:

 

Equation Mean +/- SD r r2 % MEE t P
 24-hour MEE  2343 +/- 517          

 HBE-ABW

 1465 +/- 287  0.747  0.55

 63.4 +/- 9.1

 -34.78

 <0.0001

 HBE-ABW x 1.3  1904 +/- 374  0.747  0.55  82.4 +/- 11.9  -12.87  <0.0001
 HBE-ABW x 1.6  2344 +/- 460  0.747  0.55  101.4 +/- 14.6  0.82  0.4136
 HBE-HE  1379 +/- 259  0.710  0.50  59.8 +/- 9.2  -37.73  <0.0001
 HBE-HE x 1.3  1793 +/- 336  0.710  0.50  77.8 +/- 12.0  -16.05  <0.0001
 HBE-HE x 1.6  2206 +/- 414  0.710  0.50  95.7 +/- 14.8  -2.50  0.0147
 HBE-AiBW  1415 +/- 276  0.723  0.52  61.3 +/- 9.0  -37.34  <0.0001
 HBE-AiBW x 1.3  1839 +/- 359  0.723  0.52  79.6 +/- 11.7  -15.1  <0.0001
 HBE-AiBW x 1.6  2263 +/- 441  0.723  0.52  98.0 +/- 14.4  -1.20  0.2328
 Swinamer  2142 +/- 355  0.791  0.62  92.9 +/- 11.6  -5.32  <0.0001
 Frankenfield  2110 +/- 649  0.728  0.52  89.7 +/- 19.6  -4.55  <0.0001
 Frankenfield x SF  3673 +/- 976  0.755  0.46  157.4 +/- 30.3  16.39  <0.0001
 Ireton-Jones  1933 +/- 251  0.490  0.23  85.1 +/- 15.7  -8.31  <0.0001
 Penn State-ABW  2022 +/- 393  0.813  0.66  87.3 +/- 10.8  -10.23  <0.0001
 Penn State-HE  1928 +/- 365  0.783  0.61  83.4 +/- 11.1  -13.00  <0.0001

 Penn State-AiBW

 1967 +/- 380  0.797  0.63

 85.0 +/- 10.5

 -12.35

 <0.0001

ABW = actual body weight, AiBW = adjusted body weight, HE = reference using Hamwi

Equation +/-10% +/- 15% +/- 20%

 HBE-ABW

 0%  3%  5%
 HBE-ABW x 1.3  21%  44%  56%
 HBE-ABW x 1.6  51%  73%  84%
 HBE-HE  1%  3%  3%
 HBE-HE x 1.3  15%  24%  36%
 HBE-HE x 1.6  51%  69%  85%
 HBE-AiBW  0%  3%  3%
 HBE-AiBW x 1.3  17%  32%  44%
 HBE-AiBW x 1.6  47%  69%  88%
 Swinamer  55%  64%  88%
 Frankenfield  43%  52%  63%
 Frankenfield x SF  7%  11%  12%
 Ireton-Jones  28%  43%  63%
 Penn State-ABW  39%  57%  72%
 Penn State-HE  20%  48%  64%

 Penn State-AiBW

 29%  52%  69%

Other Findings

All equations correlated significantly to MEE via IC (P < 0.0001).

The Harris-Benedict equation using adjusted body weight multiplied by a stress factor of 1.6 and the Swinamer equation predicted MEE within 20% of indirect calorimetry values 80% of the time for the entire population studied.

For those individuals at the lower weight range, the Harris-Benedict equation using actual weight reference weight via the Hamwi equation and via adjusted weight times a stress factor of 1.6 and the Swinamer equation predicted MEE within 20% of indirect calorimetry values 89% of the time.

The Frankenfield equation overestimated MEE; whereas the Penn State and Ireton-Jones equations underestimated energy needs in the population studied.

Author Conclusion:
When MEE was compared with 5 formulaic equations and nomograms of kcals/kg body weight, the Harris-Benedict equation x 1.6 stress factor and the Swinamer equation were the most accurate at predicting needs within 20% of the measured values.  The Frankenfield equation overestimated MEE, whereas the Penn State and Ireton-Jones equations underestimated energy needs.
Funding Source:
University/Hospital: St. John Health System, Central Michigan University
Reviewer Comments:
24 hour IC.  Strong inclusion/exclusion criteria.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? Yes
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes