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CI: Best Method to Estimate RMR (2006)

Citation:

Dickerson RN, Gervasio JM, Riley ML, Murrell JE, Hickerson WL, Kudsk KA, Brown RO.  Accuracy of predictive methods to estimate resting energy expenditure of thermally-injured patients.  JPEN 2002;26(1):17-29. 

PubMed ID: 11833748
 
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 evaluate the bias and precision of 46 methods published from 1953 to 2000 for estimating REE of thermally injured patients.
Inclusion Criteria:
Thermally injured adult patients (with >20% body surface burn), aged 18 - 59 years of age, requiring specialized nutrition support and who had their REE measured.
Exclusion Criteria:
  • Morbid obesity
  • HIV
  • Malignancy
  • Pregnancy
  • Hepatic or renal failure
  • Neuromuscular paralysis
  • Those requiring FiO2 > 50% or PEEP >10 cm H2O
Description of Study Protocol:

Recruitment

Patients admitted to Firefighters Burn Center of Regional Medical Center at Memphis.

Design

Cross-Sectional Study.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

REE measured through indirect calorimetry and estimated through equations.

Statistical Analysis

Methods of Sheiner and Beal were used to assess bias and precision of the methods.  The formulas were considered unbiased if the 95% confidence interval for the error intersected 0 and were considered precise if the 95% confidence interval for the absolute error was within 15% of MEE.  Nominal data were evaluated by either chi-square or Fisher's exact test.  Goodness of fit of the linear model between 2 variables was assessed from the coefficient of determination, which was derived from linear correlation using the Pearson product moment correlation coefficient.  In addition to bias and precision, comparisons between the PEE by the respective methods and MEE were analyzed using the Wilcoxon matched pairs signed ranks test.  The Mann-Whitney U test was used for comparisons of 2 independent samples.

Data Collection Summary:

Timing of Measurements

One steady state measured REE measurement obtained per patient.  Measurements performed at least 2 days postsurgery for wound excision and grafting and within the first 3 weeks postinjury. 

Dependent Variables

  • RMR measured through indirect calorimetry using MetaScope metabolic cart, performed in 20-minute intervals up to a maximum of 3 intervals per patient until steady state measurements were achieved, calibrated immediately before each measurement, steady state defined as 5 consecutive 1-minute sampling intervals with a variation of <5% for oxygen consumption and carbon dioxide production, using indirect calorimetry techniques as outlined by University of Pennsylvania
  • RMR estimated using 46 equations, including Harris-Benedict and Ireton-Jones

Independent Variables

  • Patients undergoing hyperbaric oxygen or hydrotherapy were measured before leaving ICU for these procedures
  • Continuous infusion of enteral or parenteral nutrition support
  • For patients on oral intake, measurements conducted at least 2 hours postprandial
  • All patients lying in a recliner chair at rest for at least 30 minutes and in thermoneutral environment
  • No sedatives or narcotics administered before the measurement
  • Nonventilator-dependent patients receiving supplemental oxygen by nasal cannula had the oxygen discontinued for 10 minutes before the measurement

Control Variables

 

Description of Actual Data Sample:

Initial N: 24 adult patients

Attrition (final N):  24 patients, 19 male, 5 female

Age:  mean 36 +/- 12 years

Ethnicity:  not mentioned

Other relevant demographics:  Tobiasen Burn Severity Index:  7.3 +/- 2.0

Anthropometrics:

Location:  Memphis, Tennessee

 

Summary of Results:

 

Method Bias (kcals/day) Precision (error) in(kcals/day) Precision (error) in % of MEE P <
1 x BEE -1262 to -902 1082 +/- 451 39 +/- 10  

1.5 x BEE

-375 to 192

500 +/- 499

19 +/- 24

NS

IJ - Ventilator -67 to 546 458 +/- 356 20 +/- 20 NS
IJ - Spontaneously Breathing -804 to 846 823 +/- 598 30 +/- 29 NS

Other Findings

MEE was 2780 +/- 575 kcal/day or 158% +/- 34% of the Harris Benedict equations (1793 +/- 349 kcals/day).

Only 1 patient was hypometabolic (<90% of the BEE) and none of the patients was normometabolic (90% - 110% of the BEE).  Remaining patients were hypermetabolic.

None of the methods was precise (<15% confidence interval error).

Over 1/2 (57%) of the 46 methods had a 95% confidence interval error >30% of the MEE.

48% of the methods were unbiased, 33% were biased toward overpredicting MEE and 19% consistently underpredicted MEE.

The pre-1980s methods more frequently overpredicted MEE compared with the 1990 to 2000 (p < 0.01) and 1980 to 1989 (p < 0.05) published methods, respectively.

The most precise unbiased methods for estimating MEE were those of Milner (1994) at a mean error of 16% (confidence interval of 10% to 22%), Zawacki (1970) with a mean error of 16% (confidence interval of 9% to 23%), and Xie (1998) at a mean error of 18% (confidence interval of 12% to 24%).

The conventional "1.5 times the Harris-Benedict equations" was also unbiased and had a mean error of 19% (confidence interval of 9% to 29%).

Author Conclusion:
Thermally injured patients are variably hypermetabolic and their energy requirements cannot be precisely predicted.  It is recommended that REE be measured in thermally injured patients.  In the event that indirect calorimetry is not available, the methods of Milner et al, Xie et al and Zawacki et al were the most accurate unbiased methods of those published in the literature.  The latter 2 methods can be calculated with greater ease for the practicing clinician.  Due to the lack of precision of these methods and our goal of providing optimal nutrition support without overfeeding, an adjustment factor for estimating the difference between REE and total EE is not recommended when using these estimation techniques.
Funding Source:
University/Hospital: University of Tennessee Health Sciences
Reviewer Comments:
Inclusion/exclusion criteria well defined.  Valid IC protocol.
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
  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
  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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? 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
  2.1. 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
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? 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
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  3. Were study groups comparable? 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
  3.1. 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
  3.2. 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
  3.3. 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
  3.4. 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
  3.5. 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
  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. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? 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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.4. 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
  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. 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
  5.1. 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
  5.2. 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
  5.3. 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
  5.4. 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
  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. 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
  6.1. 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
  6.2. 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
  6.3. 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
  6.4. 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments 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
  6.7. 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
  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. 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
  7.1. 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
  7.2. 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
  7.3. 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
  7.4. 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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
  8.5. 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
  8.6. 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
  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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes