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CI: Calorie/Energy Needs (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
Determine whether caloric intake is associated with risk of nosocomial bloodstream infection in critically ill medical patients.
Inclusion Criteria:
  • admission to medical ICU between Feb 1999 and Oct 2000
  • NPO for >96 hours after MICU admission
Exclusion Criteria:
  • MICU stay <96 hours
  • DNR order written <96 hours after MICU admission
  • transfer from another ICU
  • previous MICU visit during the same hospitalization
  • participated previously in the study
  • admitted for postoperative monitoring
Description of Study Protocol:

Recruitment: All patients admitted to medical ICU between Feb 1999 and Oct 2000 meeting eligibility requirements

 
Design:  138 subjects admitted to the MICU during the study period were followed until the subject died, transferred out of the ICU or took food by mouth.  Daily caloric intake from enteral, parenteral or enteral + parenteral nutrition was recorded.  Immunomodulatory formulas and specific protocolized feed for enteral feeding and for central venous catheter insertion or maintenance were not used during the study.  Neither antimicrobial-impregnated catheters or a protocol to maintain serum glucose within predefined targets were used during the study period.

Blinding used (if applicable): Members of infection control department evaluating blood cultures were blinded.

 
Intervention (if applicable): NA

Outcome of interest was development of a nosocomial bloodstream infection (BSI)

Statistical Analysis :Post-hoc subjects were categorized into 1 of following 4 quartiles reflecting their caloric  intake based on daily % of ACCP-recommended calories ( 25 Cal/kg body weight or 27 Cal/body weight in the presence of systemic inflammatory response syndrome) and to approximately balance the numbers in each group:

  • <25%
  • 25-49%
  • 50-74%
  • >75%

Because the nutrition provided on a given day might influence future but not immediate risk of infection, a 2-day lag period between caloric intake and BSI was included in the analyses of correlations between caloric intake and BSI and between serum glucose and BSI. 

A nonparametric test of trend was first used to assess the relationship between the  potential confounders listed below and caloric intake:

  • comorbidities
  • reason for MICU admission
  • SAPS II score ( simplified acute physiology score II)
  • age
  • sex
  • MICU admission source
  • number of hospital days befor admission
  • mechanical ventilation
  • serum albumin
  • BMI at MICU admission
  • days before initiating nutrition support
  • route of nutrition

If the trend was nonsignificant, Kruskal-Wallis tests for continuous variables or Fisher's extact tests and chi-square test were used for categorical variables. 

Only subjects who were free from a nosocomial BSI during the first 96 hours hours in the MICU were included in the analysis.  Survival analyses incorporating late study entry were used for bivariate and multivariate analyses.  Kaplan-Meier curves and Cox proportional hazards were used.  Differences in Kaplan-Meier functions were assessed by log rank test.

SAPS II score, serum albumin, BMI at MICU admission, prior hospital days before MICU admission average daily serum glucose, average maximum daily serum glucose, number of MICU days prior to nutrition support, and measures of parenteral nutrition were assessed in bivariate Cox Models.  Only comorbidities and reasons for admission that were statistically significantly different (P<.05) among the categories of caloric intake were evaluated in bivariate Cox models. 

A multivariable Cox model was established using the predictors that significantly predicted BSI risk in the bivariate Cox analyses.  A two-tailed P<.05 indicated statistical significance for all analyses.

Data Collection Summary:

Timing of Measurements

At  MICU admission: comorbidities that may influence risk of infection (diabetes, chronic renal insufficiency, cirrhosis, COPD), SAPS II score, height, weight, BMI, ideal body weight, serum glucose, use of mechanical ventilation

Daily: caloric intake,  average daily serum glucose concentration

Mean average and maximum daily glucose during each subject's MICU stay.

 
Dependent Variables

  • development of a nosocomial BSI in the MICU as defined by the CDCs' criterion, categorized as primary (bacteremia or fungemia not related to infection at another site) and secondary.

Independent Variables

  •  Caloric intake

 

Description of Actual Data Sample:

Initial N:  All subjects 138 (53.6% male)

Age: 52.6+16.4, NS difference between quartiles

Other relevant demographics:

  • NS difference between quartiles re: reason for admission, SAPS II scores, sex, source of admission, serum albumin (2.7+0.7 g/dL for all subjects), number of hospital days prior to MICU admission, mechanical ventilation during study period
  • Mean SAPS II Score 52.5 + 15,4

Anthropometrics: NS difference between quartiles for BMI

Location: Johns Hopkins, Baltimore, MD

 

Summary of Results:

Risk of BSI was significantly higher for subjects in quartile 1 who received < 25% of ACCP recommended caloric intake compared with the other quartiles of patients who received > 25% of ACCP recommended caloric intake (p<.05).

Significant predictors of the incidence of nosocomial BSI included:

  • Caloric intake (crude relative hazard 0.24, 95% CI 0.10-0.60, adjusted relative hazard 0.27, 95% CI 0.11-0.68)
  • SAPS II score at MICU admission (crude relative hazard 0.1.27, 95% CI 0.01-0.60, adjusted relative hazard 1.01, 95% CI 0.99-1.6

In multivariable analysis, subjects who received > 25% of ACCP recommended caloric intake had a 73% hazard reduction (95% CI 32-89%) for nosocomial BSI vs subjects in quartile 1, after adjustment for SAPS II scores.  The association between higher caloric intake and decreased hazard for BSI persisted when the analysis was stratified for subjects who received enteral nutrition alone vs any parenteral nutrition (0.35, 95% CI 0.09-146 and 0.19, 95% CI 0.06-0.63, respectively)

Author Conclusion:
Provide at least 25% of recommended calories to reduce risk of nosocomial BSI. This caloric level may not provide enough energy to achieve other important clinical outcomes.
Funding Source:
Government: NIH
Not-for-profit
0
Foundation associated with industry:
Reviewer Comments:

Effects of providing more calories than this level were not elucidated by this study.

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? 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.) 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? 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.) Yes
  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? 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.) N/A
  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? N/A
  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? No
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? N/A