CI: Enteral Nutrition Energy Delivery (2012)


Faisy C, Lerolle N, Dachraoui F, Savard JF, Abboud I, Tadie JM, Fagon JY. Impact of energy deficit calculated by a predictive method on outcome in medical patients requiring prolonged acute mechanical ventilation. Br J Nutr. 2009 Apr; 101 (7): 1,079-1,087. PMID: 18778528.

PubMed ID: 18778528
Study Design:
Retrospective Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To identify determinants of energy balance as determined by an equation and relationship to ICU outcome among severely-ill patients requiring prolonged acute mechanical ventilation and who are exclusively receiving EN.

Inclusion Criteria:
  • Adult patients admitted to the ICU over a one-year period
  • Required endotracheal intubation and mechanical ventilation fewer than six hours after ICU admission
  • Remained intubated for at least seven days.
Exclusion Criteria:

Patients were excluded if they were:

  • Intubated over six hours after ICU admission
  • Intubated for less than seven days
  • Not receiving EN due to complete intestinal obstruction or ileus, intractable vomiting or severe diarrhea, intestinal ischemia, gastrointestinal hemorrhage and high-output enterocutaneous fistulas
  • Missing or incomplete data.
Description of Study Protocol:
  • Recruitment: Admission to the ICU
  • Design: Retrospective cohort (divided into ICU survivors or deaths)
  • Intervention: Not applicable.

Statistical Analysis

  • Paired T-tests, Mann-Whitney or Fisher's tests were applied for comparison of relevant variables
  • Logistic regression was used for multi-variate analysis
  • Mantel-Haenszel tests were used to assess the relationship between ICU mortality and quartiles of mean energy balance
  • A receiver operating characteristics curve was generated with non-parametric method to determine the best operating point as mean energy deficit threshold for predicting ICU mortality
  • Kaplan-Meier curves were used to analyze ICU survival with comparison between groups determined by log-rank tests
  • StatView 4.5 and EPI INFO 3.4 software were used to calculate statistical analysis
  • Statistical significance was set at P<0.05.
Data Collection Summary:

Timing of Measurements

  • Baseline
    • Age
    • Height
    • Weight
    • Main diagnosis
    • Simplified Acute Physiology Score II (SAPS II)
    • Diagnosis of septic shock in the presence of documented infection (bacteremia, urinary tract infection and pneumonia).
  • Each day of mechanical ventilation (retrospectively collected from charts prospectively completed by nurses)
    • Weight measured with a mobile electronic scale
    • Temperature (mean of four values, measured electronically in the ear at six-hour intervals during the day)
    • Minute ventilation (mean of four values, determined with the respiratory device at six-hour intervals during the day).
  • Assessed from charts
    • Total duration of EN interruptions (expressed as a percentages of survey time) due to:
      • Gastrointestinal intolerance (vomiting, severe diarrhea, ileus)
      • Diagnostic and therapeutic procedures.
    • Estimated total length (percentage of survey time) of conditions that could decrease nutrient absorption or limit the volume of feeding rate prescription:
      • Use of sedatives, opioids, neuromuscular blocking agents or vasopressors
      • Presence of renal failure (defined as creatinine clearance <50 ml per minute) with fluid overload.

Dependent Variables

  • Mortality
  • Prolonged mechanical ventilation.

Independent Variables

  • Energy balance
    • Total energy prescribed, as calculated from glucose infusions and exclusive EN prescriptions
    • Energy delivered was determined by documentation by nursing, including EN and glucose infusions actually administered per day
    • Recommended energy was the target feeding prescription
    • Daily REE was retrospectively calculated with the following predictive equation: (8 x body weight in kg) + (14 x height in cm) + (32 x minute ventilation in liters per minute) + (94 x body temperature in degrees Celsius) - 4,834
    • Energy balance (expressed as kJ per day of mechanical ventilation) was calculated as follows: Energy delivered - calculated REE
    • Energy deficit was assumed to be the same as negative energy balance.

Other Variables

  • EN was to be started within 24 hours of ICU admission
  • Target feeding recommendations were 125.5kJ per kg (30kcal per kg) per day or per kg ideal body weight per day if body mass index (BMI) was over 25kg per m2
  • Patients received a polymeric isoenergetic solution, delivered by continuous, pump-driving infusion via nasogastric tubes.
Description of Actual Data Sample:
  • Initial N: 42 of 684 (6%) consecutive patients admitted to the ICU were eligible for analysis; four eligible patients were excluded because of incomplete or missing files; 38 patients were included (55% male)
  • Final N: 38
  • Age: Mean, 67.1 years
  • Ethnicity: Not described.

Other Relevant Demographics

  • Mean length of stay before ICU admission: 6.1 days
  • Mean SAPS II at ICU admission: 45.6
  • Mean length if ICU stay: 28.0 days
  • Mean length of invasive ventilation: 23.4 days
  • ICU death: 27 patients (72%).


  • Mean height at ICU admission: 167.1cm
  • Mean weight at ICU admission: 71.6kg.

Other Relevance Characteristics

  • 20-bed medical ICU at a tertiary teaching hospital
  • Main diagnoses at ICU admission:
    • Septic shock (N=19)
    • Acute respiratory failure due to congestive heart failure (N=11)
    • Acute respiratory distress syndrome (N=4)
    • Non-traumatic coma (N=4).


Paris, France.

Summary of Results:

Key Findings

Impact of energy balance on ICU mortality

  • ICU mortality was 72%
  • Mean energy balance was -5,439±222kJ per day (1,300±53kcal per day)
  • Total of 71% of the energy prescribed was delivered
  • Mean energy deficit was higher among non-survivors than survivors (P=0.004)
  • Energy deficit was independently associated with ICU death (P=0.02)
  • Higher ICU mortality was seen as energy deficit increased (P=0.003)
  • Higher ICU mortality was observed among patients with a mean energy deficit of at least 5,021kJ per day (1,200kcal per day) of mechanical ventilation after ICU Day 14 (P=0.01).

EN interruption

  • EN was interrupted due to procedures or severe gastrointestinal intolerance for 23% of the survey time, which may have explained the differences between delivered and prescribed energy
  • Situations (use of sedatives, opioids, neuromuscular blocking agents, vasopressors, renal failure with fluid overload) that limited administration of EN reached 64%.
Author Conclusion:

Large negative energy balance may be an independent determinant of ICU mortality among patients requiring prolonged acute mechanical ventilation, especially when energy deficit exceeds 5,021kJ per day (1,200kcal per day).

Funding Source:
University/Hospital: Service de Reanimation Medicale, Hopital Europeen Georges Pompidou, Paris, France
Reviewer Comments:

This study may have been under-powered.

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) N/A
  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) N/A
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? N/A
  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) N/A
  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.) 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
  3.5. 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? 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? 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? Yes
  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.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  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? 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? 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