CI: Best Method to Estimate RMR (2010)

Study Design:
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Quality Rating:
Research Purpose:
To determine whether the energy expenditure of mechanically ventilated multiple trauma patients correlates with the severity of injury and illness indices before important systemic infection has complicated the clinical course, and to compare the energy expenditure with the energy expenditure expected from the Harris-Benedict equation adjusted with correction factors for trauma.
Inclusion Criteria:

All adult patients with multiple trauma who required mechanical ventilation.

Exclusion Criteria:

Excluded if:

  • not hemodynamically stable
  • required vasoactive medications, fluids, colloid solutions, or packed RBC to maintain arterial pressure
  • were ventilated with positive-end-expiratory pressure > 10 cm H20 and with peak airway pressure > 60 cm H20
  • had air leaks in the ventilator circuit and in the endotracheal tube
  • required an inspired oxygen concentration > 60%
  • had uncontrollable restlessness or gross motor activity
  • had confounding variables such as sepsis and repeated operations
  • had a BMI < 18
  • had an Injury Severity Score < 20
  • were receiving glucose at a rate >100 g/day
  • had diabetes mellitus, malignant disease, or other preexisting metabolic disorders
  • were receiving systemic steroids
Description of Study Protocol:


Patients from a general ICU of a university teaching hospital.


Cross-sectional study.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

RMR measured using indirect calorimetry and estimated with equations.

Statistical Analysis

Normality of distribution was tested using Lilliefors test.  One-way ANOVA with repeated measures was carrie d out to clarify effects of time on measured hemodynamic, respiratory and blood gas parameters.  Posthoc comparisons were done with Scheffe F-test.  The bias and precision were analyzed by the Bland-Altman method.  The Student's t test was employed to determine the difference between paired and unpaired variables.  The degree of association between the variables was determined by the Pearson's product moment correlation.  All variables with significant correlation (p < 0.05) with total EE were employed in a stepwise multiple regression model using a forward elimination procedure.

Data Collection Summary:

Timing of Measurements

Indirect calorimetry measured at least 48 hours after admission.  Body weight and height taken at time of admission.

Dependent Variables

  • RMR measured with indirect calorimetry, using the Deltatrac Metabolic Monitor II, at least 48 hours after ICU admission by continuous indirect calorimetry for consecutive 12 hours, from 7 pm - 7 am, patient lying supine, motionless, not disturbed and with no major procedures performed within 60 minutes of the measurement, calibrated before each study and every 6 hours during the study
  • RMR estimated with Harris-Benedict equation without adjustments
  • RMR estimated with Harris-Benedict equation adjusted with correction factors from Long et al:  activity factor of 1.2 for bed rest, and a stress factor for trauma:  1.35 for skeletal trauma

Independent Variables

  • Data on admission to the emergency dept and during the first 24 hours of ICU admission were collected for computation of severity of injury and illness indices, respectively - Injury Severity Score, Revised Trauma Score, Glasgow Coma Scale score, Simplified Acute Physiologic Score II (SAPS II) and APACHE II score 
  • ICU activity (tracheobronchial suction, turning, blood drawingf, dressing changes, and nursing care) allowed without restriction and recorded
  • Every 6 hours, physiologic variables recorded:  minute ventilation, body temperature, heart rate, invasive systolic, diastolic and mean arterial pressure, FIO2, positive end expiratory pressure and blood gas analysis

Control Variables


Description of Actual Data Sample:

Initial N: 42 multiple trauma patients admitted consecutively

Attrition (final N):  16 excluded based on exclusion criteria.  26 completed the study, 22 males, 4 females.

Age:  37 +/- 21 years

Ethnicity:  Not mentioned.

Other relevant demographics:  mean BMI:  24.2 +/- 2.5 

Anthropometrics: mean APACHE II score:  18.2 +/- 4.7

Location:  Italy


Summary of Results:





1963 +/- 427


1975 +/- 406

REE by H-B

1647 +/- 238

TEE by adjusted H-B 2595 +/- 369

Other Findings

No statistically significant correlations were observed between both REE and total EE and the Injury Severity Score, Revised Trauma Score, Simplified Acute Physiologic Score II, APACHE II score, and Glasgow Coma Scale score.

Statistically significant correlations between total EE and the individual clinical and anthropometric parameters were observed for heart rate (p = 0.02, r2 = 0.21), body temperature (p = 0.01, r2 = 0.24), minute ventilation (p = 0.01, r2 = 0.42), age (p = 0.02, r2 = 0.18), height (p = 0.01, r2 = 0.27), body weight (p = 0.01, r2 = 0.43), and Harris-Benedict equation (p = 0.01, r2 = 0.57).

A regression model of total EE was developed with the following variables:  Harris-Benedict equation, heart rate, and minute ventilation (p = 0.01, r2 = 0.74).

REE was significantly different from the EE estimated from Harris-Benedict alone:  bias was 289 +/- 326 kcal/day and 95% of the errors were within -363 kcal/day to 941 kcal/day.

Total EE was also significantly different from EE estimated with adjusted Harris-Benedict:  bias was -619 +/- 273 kcal/day and 95% of the errors were within -73 kcal/day to -889 kcal/day.

The REE/predicted basal EE ratio was 1.17 +/- 0.2 and the total EE/predicted total EE ratio was 0.76 +/- 0.1.



Author Conclusion:
In conclusion, this study shows that in mechanically ventilated multiple trauma patients, the energy expenditure is not correlated to the severity of injury and illness indices but is dependent on the Harris-Benedict equation in addition to heart rate and minute ventilation.  Furthermore, this patient population is characterized by a moderate state of hypermetabolism, and the Harris-Benedict prediction modified with correction factors for trauma systematically overestimates the total energy expenditure.  The moderate state of hypermetabolism probably represents the effect of reduced trauma response, most likely because of the absence of confounding factors and to the use of sedation and mechanical ventilation.
Funding Source:
Reviewer Comments:
Inclusion/exclusion criteria and recruitment methods well defined.  Overnight measurements might have captured some sleeping EE which would be lower than REE.  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
  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? 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
  3.3. 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? N/A
  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.) 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
  4.1. 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? Yes
  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? 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