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CI: Best Method to Estimate RMR (2006)

Citation:

Ahmad A, Duerksen DR, Munroe S, Bistrian BR.  An evaluation of resting energy expenditure in hospitalized, severely underweight patients.  Nutrition 1999;15(5):384-8. 

PubMed ID: 10355852
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To assess the accuracy of the commonly used formulae in this select group of patients as a best estimate.
Inclusion Criteria:
Severely malnourished/underweight hospitalized patients, referred for nutritional support.  All patients included who agreed to be studied and who were reasonable candidates.
Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:

Recruitment

Methods not specified.

Design

Cross-sectional study.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

RMR measured with indirect calorimetry and estimated with equations. 

Statistical Analysis

All values expressed as mean +/- SD.  Paired t tests were used to compared measured with estimated values, and linear regression analysis was employed to determine correlations between MREE, estimated REE, and weight.  In addition to the best fit equation, the correlation of MREE and weight without a constant was defined.  ANOVA was employed to test the significance of these equations.  

Data Collection Summary:

Timing of Measurements

Prospective trial of indirect calorimetry measurements and information for equations.

Dependent Variables

  • RMR measured with Sensormedics Deltatrac MBM100 indirect calorimeter, measured until recordings were in steady state for 15-20 minutes, calibrated before each measurement 
  • RMR estimated using Harris-Benedict formula with no adjustments
  • RMR estimated using 25 kcal/kg body weight

Independent Variables

  • All patients being fed intravenously with TPN or enteral feeding at time of study
  • Nutritional assessment (including weight, height, triceps skin fold thickness, and midarm circumference) and a creatinine height index were preformed
  • Patients were chosen when afebrile or with only minimal temperature elevations, and with a normal white blood cell count or minimally elevated leukocytosis

Control Variables

 

Description of Actual Data Sample:

Initial N: 12 hospitalized patients (9 women, 3 men), 7 ventilated, 5 not ventilated

Attrition (final N):  12

Age: mean age 66.5 +/- 13.9 years, range 34 - 83 years

Ethnicity:  not mentioned

Other relevant demographics:  mean weight 40.9 +/- 5.1 kg (range 32 - 50 kg), 70.7 +/- 7.8% IBW

Anthropometrics: 

Location: Massachusetts

 

Summary of Results:

 

Patient

Indirect Calorimetry Harris-Benedict 25 kcal/kg MREE (kcal/kg)

1

1600  1076  1215 32.9

2

1200 

973 

800 

32.5 

3 990  946  925  26.9 
4 1215  1049  1035  29.2 
5 1500  1064  1250  30.0 
6 1350  1153  950  35.5 
7 1400  1002  1072  32.6 
8 1200  1087  988  30.4 
9 1220  918  890  34.0 
10 1370  1076  1008  33.9 
11 1300  1016  1112  29.2 
12 1240  1026  1025  30.2 

Mean +/- SD

1300 +/- 160 

1032 +/- 66 

1023 +/- 129 

31.4 +/- 2.5

Other Findings

Each patient had either an arm muscle circumference less than the fifth percentile or a creatinine height index less than 60% standard, confirming severe muscle depletion in all.

Results by Harris-Benedict (1032 +/- 66 kcal) and 25 kcal/kg (1023 +/- 129 kcal) were significantly lower than the MREE (1300 +/- 160 kcal) in this group of patients (P < 0.0001).  The MREE exceeded the estimated REE in each individual.

The percentage difference between MREE and estimated REE by the Harris-Benedict formula was 18.4 +/- 9.4%, and 20.9 +/- 7.5% by the empirical formula.

The correlation between MREE and body weight (r = 0.747, P = 0.005) was better than that between MREE and estimated REE by Harris-Benedict formula (r = 0.524, P = 0.08) suggesting that weight was the principal determinant rather than the other components (height, age, sex) of the Harris-Benedict formula.

 

Author Conclusion:
In summary, critically ill patients who are severely underweight (below 50 kg in body weight) have MREE that are substantially higher than those predicted by the Harris-Benedict equation or an empirical formula of 25 kcal/kg body weight.  The Harris-Benedict equation had limited predictive value for the individual, explaining approximately 25% of the variance in energy expenditure.  However, an empirical formula at 30 - 32 kcal/kg provides a reasonable estimate of MREE for clinical purposes and has a better correlation with the MREE than the Harris-Benedict equation.  A hypothesis is presented that suggests that a relative preservation of visceral organs over skeletal muscle, in response to illness, is largely responsible for these findings.
Funding Source:
University/Hospital: Beth Isreal DeaconeseMedical Center
Reviewer Comments:
Small sample size; inclusion/exclusion criteria and recruitment methods not well defined.
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? ???
  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? ???
  2.2. Were criteria applied equally to all study groups? ???
  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? ???
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? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  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)? Yes
  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