EE: Respiratory Quotient (RQ) (2013)

Citation:

Zauner C, Schuster BI, Schneeweiss B. Similar metabolic responses to standardized total parenteral nutrition of septic and nonseptic critcally ill patients. Am J Clin Nutr. 2001;74:265-270

 
Study Design:
Prospective Cohort Study
Class:
B - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
  1. To evaluate energy and substrate metabolism in septic and nonseptic critically ill patients in the resting state and during the administration of standardized total parenteral nutrition.

Definitions

  • Steady state:
  • Sepsis: Am Coll Chest Phys/Soc Crit Care Med Consensus Conference -- if infection sit was established and =2 following: temp >38 or <36°C, heart rate >90 beats/min, respirator rate >20 breaths/min or arterial part press of CO2<32 mmHg, and WBC >12 or <4 109/L or >10% immature band forms.
  • Severity of sepsis: On day 0 assess by SOFA (sepsis-related organ failure assessment) score
  • Nonsepsis: Those failure to meet consensus conference criteria w/no infection evidence
  • Severity of illness: Use of APACHE III score
Inclusion Criteria:
  1. Understand and give written consent
  2. Diseases in subjects that were allowed: sepsis
  3. Medications allowed:
Exclusion Criteria:
  1. Refusal to consent
  2. Not meeting inclusion criteria
  3. Diseases in subjects that were excluded: pre-existing diabetes mellitus or hereditary disturbance of lipid metabolism.
  4. Additional conditions: hemodynamic shock with serum lactate conc >5 mmol/L, or 450 mg/dL, and hyperglycemia (ie., glucose >10 mmol/L, or 180 mg/dL despite continuous admin insulin at 30µmol/h (5 IU/h) before TPN administration
  5. Additional conditions: pts w/ artificial ventilation at >0.55 FIO2.
Description of Study Protocol:

ANTHROPOMETRIC

  • Ht measured? Likely
  • Wt measured? Likely
  • Fat-free mass measured? No

CLINICAL

  • Monitored heart rate? Yes
  • Body temperature? Yes
  • Medications administered? Not specified; likely

Resting energy expenditure

  • IC type: MMC 2900;
  • Equipment of Calibration: Yes
  • Coefficient of variation using std gases: No
  • Rest before measure (state length of time rested if available): Yes
  • Measurement length: 30 min
  • Steady state: Not specified
  • Fasting length: Day 0, before TPN started
  • Exercise restrictions XX hr prior to test? Not applicable
  • Room temp: In Vienna hospital
  • No. of measures within the measurement period: 30 1-min measures
  • Were some measures eliminated? No
  • Were a set of measurements averaged? Yes
  • Coefficient of variation in subjects measures? Not specified
  • Training of measurer? Very likely
  • Subject training of measuring process? Not specified.

DIETARY

  • TPN soln containing 45% gluc; 41% lipids; 14% amino acids; infusion rate remained unchanged during the whole studyperiod; REE and substrate oxidation rates re-evaluated on days 2 and 7.

Intervening factor:

Data Collection Summary:

Outcome(s) and other measures

  1. Measured REE [(VO2 l/min), VCO2 (l/min; ml/kg/min), RQ, nonprotein RQ, ventilation (l/min)].
  2. Clinical: Temp, heart rate, RF, PcCO2, WBC, Mean arterial pressure, SOFA score
  3. Serum urea, glucose, lactate, Triacylglycerol, Chol, Dretinine, UNP
  4. Dietary oxidation rates for CHO, FAT, PRO
  5. Anthropometric variables: weight, height, age, BMI,and fat-free m O2s, fat mass.

Blinding used: Yes

Description of Actual Data Sample:
  • N=25 patients
  • 15 men; 10 women
  • Mean age, y: 56.1±15.1

Statistical tests

  • Mann-Whitney U test
  • Repeated ANOVA, if repeated ANOVA significant, linear contrasts were used
  • Chi-square test to compare mortality and sex distribution
  • Spearman’s rank correlation.
Summary of Results:

ANTHROPOMETRIC

Septic (8 M; 6 F) Mean±SD

Age, y

57.5±12.9

Wt, kg

71.4±12.7

Ht, cm

172±8.3

BMI

24.1±4.2

Nonseptic (7 M; 4 F) Mean±SD

Age, y

64

Wt, kg

65.5±12.9

Ht, cm

173±9.5

BMI

21.8±3.5

Septic patients

Diseases represented include liver transplantation, multiple organ failure, CABG, CPR, cirrhosis, burn, duodenal ulcer perforation. APACHE III socres ranged from 51 to 86 and SOFA score of 5 to 15.

Nonseptic patients

Diseases include CABG, cardiomyopathy, COPD, CPR, GI, and kidney transplantation. APACHE III score range from 63 to 126.

The severity of illness by the APACHE III score was not significantly different between groups (P>0.05). The APACHE III score correlated negatively with mearued REE in septic patients (r= -0.58, P<0.05). This association not found in nonseptic patients.

RESTING ENERGY EXPENDITURE

REE was positively correlated with body temperature in septic patients (12.2% rise in REE/°C rise). No association between body temperature and APACHE III score was found in either group.

REE was not significantly different between groups on day 0, and no significant difference in REE were detected between groups during the study period.

RESPIRATORY QUOTIENT

RQ increased significantly in both groups on day 2 [Analyst note: TPN started after day 0 measure] compared with Day 0 and remained high on day 7. No significant differences were observed on days 0, 2, and 7.

Septic (8 M; 6 F) Day 0
Mean±SD
Day 2
Mean±SD
Day 7
Mean±SD

RQ

0.77±0.05 0.84±0.05 0.86±0.05*

REE, kj/min/m m2

2.65±0.5 2.69±0.5 2.55±0.7

Nonseptic (7 M; 4 F) Day 0
Mean±SD
Day 2
Mean±SD
Day 7
Mean±SD

RQ

0.75±0.05 0.84±0.04 0.82±0.04**

REE, kj/min/m2

2.65±0 m2 2.69±0.5 2.55±0.7

  • * P<0.01
  • ** P<0.05
Author Conclusion:

As stated by the author in body of report

In our study, No significant differences in measured REE and substrate oxidation rates after an overnight fast existed between septic and non-septic critically ill patients. Infusion of a standardized TPN formula results in no significant changes in REE between or within groups during the study period.”

“Body temperature was positively correlated with REE in septic patients and agrees with Frankenfeld [sic] and the amount 12$/°C agrees with DuBois and Wallace et al.”

“RQ rose in both groups after th initiation of TPN and incontrast with healthy subjects and nutritionally depleted patients, RQ in the subjects never exceeded 1.0, indicating that no net de novo lipogenesis was present (i.e., total liid oxidation was higher than total lipid synthesis) despitie positive energy and substrate balances.”

“In conclusion, septic and nonseptic critically ill patients weem to show the same alterations in ergy and substrate metabolism. A disease-specific macronutrient composition of a TPN formula soes not seem to be necessary for septic or nonseptic critically ill patients.”
Funding Source:
University/Hospital: University of Vienna (Austria)
Reviewer Comments:

Strengths

  • “Well-designed research protocol with clear explanations and use of validated tools (e.g., APACHE III, SOFA, indirect calorimetry measures.”

Generalizability/Weaknesses

  • “Generalizable to critically ill patients with planned use of TPN; cannot be generalized to patients receiving enteral nutrition ”
  • “Unable to determine if all patients were artificially ventilated”
  • Important variables on REE measurement accuracy included a discussion on steady state and since medications (e.g., pain, sedation, or chemical paralysis) not discussed unable to determine steady state achievement.”
[Analyst note: author reports 43% mortality in septic and 64% mortality in nonseptic patients; study data reports all participants; unclear of time beyond 7-day study period that mortality data was measured.]
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? N/A
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? N/A
  1.3. Were the target population and setting specified? N/A
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? N/A
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? N/A
  2.4. Were the subjects/patients a representative sample of the relevant population? N/A
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.) 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? 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? No
  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? 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? 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? N/A
  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? N/A
  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? No
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.2. Were nutrition measures appropriate to question and outcomes of concern? N/A
  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? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? N/A
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? N/A
  8.2. Were correct statistical tests used and assumptions of test not violated? N/A
  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? N/A
  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? N/A
  9.2. Are biases and study limitations identified and discussed? N/A
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.2. Was the study free from apparent conflict of interest? N/A