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CKD: Energy Requirements (2009)

Citation:

Kuhlmann U, Schwickardi M, Trebst R, Lange H. Resting metabolic rate in chronic renal failure.  J Renal Nutr 2001; 11:202-206.

Worksheet created prior to Spring 2004 using earlier ADA research analysis template.
PubMed ID: 11680000
 
Study Design:
Cross-Sectional Study
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

The purpose of this study was to determine the association of CRF on the resting metabolic rate (RMR) in subjects with pre-ESRD.

Inclusion Criteria:

1. Impaired kidney function

a. creatinine clearance (CrCl) between 6 and 60 mL/min.

b. blood urea between 12 and 22 mmol/L

c. mean hemoglobin of 10.8+0.92 g/dL

Exclusion Criteria:

1. Acute inflammation

2. Erthyropoietin therapy

3. Comorbid conditions: uncontrolled hypertension, insulin-dependent diabetes, thyroid dysfunction, acute or chronic infections, malignoma, or other severe diseases.

4. ß-receptor blocking agents or thyroid hormone

Description of Study Protocol:

Recruitment

Methods not described.

Design 

1. Direct calorimetry used to measure resting metabolic rate (RMR) with a metabolic beam scale:

    a. subjects were at rest for 30 minutes in an a controlled environment (temperature, humidity, air velocity).

    b. normal physical activity for 3 days prior to testing.

    c. fasting for 12 hr prior to testing

2. Evaporative heat loss and dry heat loss measured and summed.

3. Creatinine clearance determined by 24-hr urine and blood sampling on the day of the RMR determination.

Blinding Used (if applicable):  not applicable

Intervention (if applicable):

Direct calorimetry for RMR determination.

Statistical Analysis 

Wilcoxon test used for paired data, Whitney-Mann rank-sum test used for unpaired data.  The correlation obtained from normal distributed data was analyzed by the product-moment correlation test.

Data Collection Summary:

Timing of measurements

For longitudinal study: baseline, 3 months, 6 months.

Dependent Variables

  • Resting metabolic rate measured by direct calorimetry
  • Creatinine clearance determined by urine and blood sampling

Independent Variables

  • Fasted state, at rest for 30 minutes in controlled environment

 Control Variables

Description of Actual Data Sample:

Initial N:  51 subjects participated in the cross-sectional study (31 men, 20 women).  22 of these also participated in the longitudinal study.

Attrition (Final N):  See above

Age:  53.2 +/- 13.9 years

Ethnicity:  not mentioned

Other relevant demographics and anthropometrics:

Baseline demographics:

Age, yr

53.2+13.9

Height, cm

168.73+5.93

Weight, kg

68.03+6.96

Causes of kidney disease

%

Glomerulonephritis

50.9

Obstructive nephropathy

13.7

Analgesic nephropathy

5.9

Polycystic kidney disease

5.9

Diabetic nephropathy

21.6

Location: Phillips-University of Marburg, Germany

Summary of Results:

Cross-Sectional Study

CrCl in ml/min was 18.69 +/- 11.98

RMR in kcal/kg/1.73 m2 was 1.095 +/- 0.04

There was a negative correlation between RMR/BW and body surface area: r = - 0.557 (P<0.001) and between RMR/BW and CrCl (r = -.763, p <.001).

Longitudinal Study

 22 of the subjects had RMR and CrCl repeated at 3 and 6 months

 

Time (months)

  0 3 6

CrCl, ml/min

27.5+9.5

19.4+6.25

13.0+3.8

RMR, kcal/kg/1.73 m2

1.05+0.03

1.09+0.40

1.12+0.04

RMR, kcal/kg body weight/day

23.5+1.5

24.3+1.5

25.2+1.5

There were no significant differences in body weight over the 6-month study period.

 CrCl dcreased over the 6 month study period by about 50%. The RMR, however increased.

Author Conclusion:

Taking into account the reduced oxygen consumption of the shrinking kidneys, the normal RMR suggests an increased energy expenditure per body cell mass. The raising RMR in deteriorating excretory kidney function reflects the increased energy expenditure in progressive chronic renal failure.

Funding Source:
University/Hospital: Philipps-University of Marburg
Reviewer Comments:

The measurement of RMR by direct calorimetry would be more precise than by indirect calorimetry. The estimated differences in energy requirement (RMR) at baseline compared to 6 months after the CrC had decreased ~50%, was an increase of ~100 kcal/d.

These results are similar to other studies that report 0.9 to 1.0 kcal/kg/1.73 m2 in patients with chronic kidney disease.

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? N/A
  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.) No
  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.) 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? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? 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
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? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? 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? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  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? N/A
  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? N/A
  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? No
  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