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CI: Individual Equations (2010)

Citation:

Cutts ME, Dowdy RP, Ellersieck MR, Edes TE.  Predicting energy needs in ventilator-dependent critically ill patients:  effect of adjusting weight for edema or adiposity.  Am J Clin Nutr 1997;66:1250-6. 

PubMed ID: 9356545
 
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 ability of a proposed technique (using an adjusted weight rather than actual or ideal) to improve the accuracy of predicting energy needs in ventilator-dependent, critically ill, overweight subjects.
Inclusion Criteria:
Ventilator-dependent adult patients.
Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:

Recruitment

Patients in the medical or surgical ICUs of 3 hospitals.

Design

Cross-Sectional Study. 

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

RMR measured with indirect calorimetry and estimated with equations.

Statistical Analysis

A split-plot ANOVA was conducted to look for differences between combinations of prediction methods and groups of overweight subjects.  Mean differences were determined by using Fisher's least significant difference method.  Further ANOVA was conducted using a one-way ANOVA examining relative energy needs by percentage IBW group and diagnosis.  Simple regression analysis was performed for each method versus REE for each percentage IBW group. 

Data Collection Summary:

Timing of Measurements

Retrospective review of charts for indirect calorimetry and information for equations.

Dependent Variables

  • RMR measured with indirect calorimetry by trained technicians using the 2900 Sensor Medic Metabolic Cart, Sensor Medic Deltra Trac, or CPXCCM MedGraphics Metabolic Cart.  Measurements performed according to each institutions' protocols, which were similar.  Subjects in resting state for >30 min before measurement, readings excluded if patients were receiving oxygen concentrations >60% or if steady state not obtained
  • RMR estimated using Harris-Benedict equation
  • RMR estimated using kJ per kg
  • Equations used both actual and adjusted weight [IBW + (actual - IBW) X 0.25]
  • IBW for males calculated as: 48.2 for first 1.54 m + 2.7 kg per additional 2.54 cm
  • IBW for females calculated as:  45.4 kg for first 1.54 m + 2.3 kg per additional 2.54 cm
  • Appliation of stress factors:  subjects were categorized as moderately or highly stressed
  • Moderately stressed:  1 or 2 organ system failures, evidence of mild to moderate infection or both, factor of 10 - 50% above baseline Harris-Benedict and 105  -146 kJ/kg
  • Highly stressed:  multiple organ system failure, sepsis or both, factor of 30 - 70% above baseline Harris-Benedict and 125 - 167 kJ/kg

Independent Variables

  • Most patients receiving enteral or parenteral nutrition support
  • Nutritional assessments performed on all subjects and included a review of current and past medical history, weight status, weight changes during admission, and medication and laboratory data
  • Attention given to signs of hydration status, edema, records of input/output 

Control Variables

 

Description of Actual Data Sample:

Initial N: 110 subjects, subjects were grouped according to IBW (<101%, 101-129%, 130-159%, >159%).  35 female, 75 male

Attrition (final N):  110 subjects

Age:  range 18 - 87 years

Ethnicity:  not mentioned

Other relevant demographics:

Anthropometrics:  IBW:  <101% (n=29), 101-129% (n=35), 130-159% (n=31), >159% (n=15)

Location:  Missouri

 

Summary of Results:

 

Percentage IBW

HBE-Adj R2 HBE-Adj Slope kJ/kg-Adj R2

kJ/kg-Adj Slope

101 - 129% (n=35)

0.2137 0.5725 0.1725 0.3980

130 - 159% (n=31)

0.4703

0.08176

0.4596

0.6776

Other Findings

Results indicated that use of actual weights in predictions for overweight subjects may lead to overfeeding.

Use of adjusted weights led to more accurate energy predictions with the KJ per kg than with the Harris-Benedict equation.

Adjusted-weight strategies could explain >45% of the variability of REE in subjects 130 - 159% of IBW. 

No significant differences were observed in REE on the basis of the presence or absence of all possible combinations of these diagnoses (P > 0.05).

Author Conclusion:
Results of this study suggest that that using adjusted weights with the KJ per kg strategy may be preferable for this population, particularly for patients > 130% IBW.  This study also indicated that multiple diagnoses may not lead to increased energy requirements.  Indirect calorimetry, when available, remains the standard for assessing and reassessing needs in those patients for whom energy balance is crucial.
Funding Source:
University/Hospital: University of Missouri, Truman Memorial Veterans Hospital
Reviewer Comments:
IC performed using different indirect calorimeters and similar but not identical protocols at the 3 hospitals.  Calibration not mentioned.  Although steady state was reached, measurement length not mentioned.  Inclusion/exclusion criteria 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? No
  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? ???
  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? ???
  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.) ???
  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? ???
  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? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? ???
  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? 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)? 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