CI: Protein Needs (2007)


Scheinkestel CD, Kar L, Marshall K, Bailey M, Davies A, Nyulasi I, Tuxen DV. Prospective randomized trial to assess caloric and protein needs of critically ill, anuric, ventilated patients requiring continuous renal replacement therapy. Nutrition 2003;19(11-12):909-16.

PubMed ID: 14624937
Study Design:
Prospective, randomized trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To access caloric and protein needs of critically ill, ventilated patients requiring continuous renal replacement therapy
Inclusion Criteria:
Critically ill ventilated patients requiring continuous renal replacement therapy (dialysis).
Exclusion Criteria:

Did not meet inclusion criteria.

Description of Study Protocol:

Recruitment 50 sequential critically ill ventilated patients

Design 6 day study w/ 50 patients randomized to control group (10 pts) or trial group (40 pts).

Blinding used (if applicable) not disclosed


  • Control Group (n=10) received 2.0 g/kg/d-1 protein throughout study
  • Trial Group (n=40) received increasing protein throughout study
    • 1.5g/kg/d-1 protein for 2 days
    • 2.0g/kg/d-1 protein for 2 days
    • 2.5g/kg/d-1 protein for 2 days

Statistical Analysis

  • Univariate analysis with chi-square test and Fisher's exact test for categorical outcomes and with Student's t tests for continuous normally distributed data. Randomization scheme not described.
  • ICU length of stay and urine volume were log-transformed before analysis.
  • Multivariate analysis was performed with multiple logistic regression and repeat measures generalized linear modeling, when appropriate. P = 0.05 was considered statistically significant.


Data Collection Summary:

Timing of Measurements

  • 3 samples of dialysate were taken 8 hrs apart beginning after 24 hr on each feeding regime for trial patients and at the equivalent time (i.e. on days 2.4.6) for control patients
  • for patients producing more than 500mL/d of urine, a urine sample was taken at the same time as the dialysate sample. Total nitrogen analysis was then performed on each dialysate (+/- urine) sample with the Kjeldahl method
  • EE measured by Schofield equation adjusted by stress factors or metabolic cart
  • EE measured over each 24 hr period throughout trial and an average EE per day was obtained.

Dependent Variables

  • Nitrogen balance (measured by analysis of dialysate and urine if any)
  • Mortality
  • Length of stay in ICU and hospital
  • Days on mechanical ventilation

Independent Variables

  • Protein intake
  • Energy intake

Control Variables

  • Blood glucose held below 12mM/L
  • CRRT


Description of Actual Data Sample:

Initial N: 50 (10 controls and 40 experimental subjects)

Attrition: 50

Age: 53.3 ± 17.4

Ethnicity: not described


  • Control group BMI: 25.7/ Stress factor: 1.39/ APACHE score: 28.7
  • Trial group BMI: 23.8/ Stress factor 1.41/ APACHE score: 25.4

Location: The Alfred Hospital, Melbourne, Australia


Summary of Results:

 Nitrogen balance was highly correlated to mortality.

  • For every 1g/d increase in nitrogen balance the probability of survival increased by 21% (p=0.03) ; odds ratio, 1.211; 95% confidence interval, 1.017, 1.443)

Nitrogen balance was not correlated with length of hospital stay, length of ICU stay, or days on ventilator.


Treatment Group


Control group


Statistical Significance of Group Difference

Nitrogen balance

became positive over time

became negative over time

Nitrogen balance changed over time (p = 0.0001)

Energy intake

 2153 ± 380 kcal/day and increased by 56 ±  24 kcal/d to 2431 ± 498kcal/d

 2153 +/- 380 kcal/day and increased by 56 +/- 24 kcal/d to 2431 +/- 498 kcal/d

Energy intake increased for both groups (p= <0.0001)

 Other Findings

  • If the predicted caloric requirement was less than 2500, the energy expenditure (EE) exceeded the predicted by an average of 19%. If the predicted caloric requirement was greater than 2500, the EE on average was 6% less than predicted. (p= 0.025)
  • Nitrogen balance was inversely related to EE (p=0.05)
  • Nitrogen balance was positively related to protein intake (p=0.0075) and more likely to be attained with protein intakes larger than 2g/kg-1/d-1 (p=0.0001)
  • Enteral feeding even after adjusting for predicted risk of death, has a statistically significant benefit to patient survival (p= 0.04)



Author Conclusion:
This study demonstrated the benefits of using a metabolic cart to avoid the under or over estimating of EE common with use of predictive formulas and  the positive relationship between nitrogen balance and protein intake. Protein amounts of more than 2 grams/kg/day were most likely to improve survival rates.
Funding Source:
University/Hospital: Alfred Hospital (Australia)
Reviewer Comments:
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? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) ???
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) 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? 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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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.) Yes
  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? Yes
  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? 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
  7.2. 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