- Click here for explanation of classification scheme.
- What is the overall effect of indirect calorimetry (IC) in critically ill patients when the IC test is consistently performed (due to adherence to a strict protocol by team members and using appropriate equipment) and metabolic measurements accurately interpreted and translated into an appropriate nutrition management?
- Identify the factors that affect the measurement of resting energy expenditure and respiratory quotient from indirect calorimetry
- Identify the potential sources of error that may occur when performing indirect calorimetry
- Describe how measurement errors may be avoided
- Describe the conditions necessary to obtain optimal results when performing metabolic tests
- Describe the clinical effect indirect calorimetry has had in the nutritional management of critically ill patients.
- None discussed.
- None discussed.
Description of Study Protocol:
- Adequate nutritional support: Provision of nutrients in such a manner that optimal patient outcome is achieved
- Adequate enteral tubefeeding: Provision of 2.5L in 72 hours (Atkinson S, Sieffert E, Bihari, 1998)
- Indirect calorimetry: Weir equation
Energy expenditure = (3.94 x VO2)+(1.11 x VCO2) such that 80% O2 consumption accounts for energy expenditure and 20% due to CO2 production (Weir JB, 1949)
- Steady state or metabolic equilibrium: A five-minute interval during which VO2 and VCO2 change by less than 10% or the coefficient of variation for these two values is <5% (Feurer ID, Crosby LO, Mullen JL, 1984; Feurer ID, Mullen JL, 1986)
- Respiratory quotient: Ratio of VCO2 to VO2; an associated physiologic range is from 0.67 to 1.3; hence, values outside this range are generated though error and beneficially used to validate IC measurement accuracy (Branson RD, 1990).
Data Collection Summary:
Outcome(s) and other measures
- Why type of information was abstracted from articles
- How was it combined?
- What analytic methods were used, if any?
Description of Actual Data Sample:
- 36 included in publication
- 10 of the 36 (28%) cited articles were written by the primary author
- Eight (22%) are narrative reviews citations
- Two (6%) each are abstracts and textbook citations
- Approximately 17 (47%) are primary research citations
- The number of articles identified in search strategy or for consideration is not stated
- Characteristics of the study participants include critically-ill, mechanically-ventilated suffering head injury, TPN and enteral nutrition patients and severely burned patients.
Summary of Results:
What Are the Main Results of the Review?
Factors that decrease value of IC
Factors that decrease value of IC
- Inadequate Enteral Tube Feeding (ETF) rates and strengths
- Underprescribing, slow startups, frequent cessations of feeds
- Physicians underorder ETF, prescribing only 65-78% of required caloric requirements, while 76-78% of prescribed calories are actually delivered [Adam S, Batson S, 1997 (UK study); Heyland D, Cook DJ, Winder B et al, 1995)
- Discontinuation r/t nursing care.
- Unknown percentage of goal calories required to maintain gut integrity and prevent bacterial translocation
- Ability to define “attenuation of stress response” and “reduce overall disease severity”
- Critically ill: Decrease in percentage of goal kcals infused; decrease in alb levels, P=0.042, 0.13 [Confounding variable: Worsening of disease?] (McClave SA, Sexton LK, Spain DA et al, 1999)
- Critically ill with mechanical ventilation: 0% on ETF had UGI BLDG, compared to 78% on acid-reducing TX alone [Pingleton SK, Hadzima SK, 1983 (retrospective)]
- Trauma: Patients receiving 59.2% of goal calories than controls (36.8%) (P=0.004) had a significant shift in the ratio of C-reactive protein to alb levels in first two-week hospitalization; decrease in fxn, decreased hospital stay,decreased rapid return to cognitive function (Taylor SJ, Fettes SB, Jewkes C et al, 1999)
- Burn patients: Incidence GI BLDG 8.3% without ETF vs. 3.3% in patients on ETF (P<0.05) (retrospective, multi-center) (Raff T, Germann G, Hartmann B, 1997)
- Critically ill: Overt GI bleed was 6% in controls vs. 5% in sucralfate and 5% in histamine2 blockers (i.e., no difference)
- Confounding possibility: 72% of controls maintained on ETF vs. 57% on ETF in histamine2 blockers. ETF had an RR of 0.35 (95% CI=0.16-0.76%; P=0.002) (Cook DH, Heyland DK, Griffith L et al, 1999)
- Adult respiratory distress SYN on ventilator: No difference if receiving some or adequate ETF. In 101 patients receiving adequate ETF, a significant difference was observed in patients receiving a sufficient volume of immune formula vs. controls given the standard formula (P<0.05) (Atkinson S, Sieffert E, Bihari, 1998).
- Bedrest for 30 mins in thermo-neutral environment
- NPO after overnight fast for pt on oral diets and those on ETF or TPN should be placed on a continuous rate before and up through time of testing
- Pts on mech vent should have stable control settings for 90 mins prior to testing
- Analgesics should be given to control pain and sedatives to control anxiety
- Avoid interruptions
- Loosening steady state criteria
- If Coefficient of variation exceeds 9.0
- Adding 10% to the REE measured by IC for activity related to nursing care
- Adding adjustments for wound healing, growth, anabolism or diet-induced thermogenesis (McClave SA, Spain DA, Skolnick J et al, 1999).
- Ideal goal is to achieve 60-70% of the goal calories to maintain gut integrity, attenuate the stress response, stress prophylaxis and promote an effect from the immune-stimulating diet
- Measuring excesses
- Critically ill: Provided 110% of calories required; RQ exceeded 1.0 in 47.1% in parenteral nutrition patients (Guenst JM, Nelson LD, 1994); but 16.0% in EFT (McClave SA, Lowen CC, Kleber JM et al, 1998)
- An appropriate upper range of less than 150% of calories provided or required is suggested for goal settings. Patient with RQ of 1.0 increased significantly from 10% to 50% only when the degree of overfeeding exceeded 150% of calories required (McClave SA, Lowen CC, Kleber MJ et al, 1998).
- Maximize delivery via enteral route: FS formula, 25cc per hour and increasing 25cc per hour Q 8 H; Residual volume of 200 is the limit. Feeding should be continuted up to four hours per test or diagnositic procedure. Ordering a volume of feeding over 18 hours (allowing an off period to make U deficits) may further enhance delivery of ETF
- Maximize delivery via TPN: Identify goal, fat calories 15-30% of overall calories, feeding advance only if glucose is controllable <200mg/dL.
- "Efforts made to measure caloric requirements by IC are meaningless unless an equal effort is made to actually provide enough calories to match requirements through nutritional support"
- "IC helps to “train” clinicians in accurate nutrition assessment and direct nutritional care"
- "Focusing on goal calories and cumulative caloric balance is a valuable practice to assure therapeutic endpoints of ETF are obtained"
|University/Hospital:||University of Louisville|
- Identifies theoretical consequences of inappropriate feeding.
- Almost 30% of reference citations were by primary author; 30 references cited.
- Uses many narrative reviews to make the case without descriptions of strengths or weaknesses of each review
- Critical info regarding RQ (i.e., low sensitivity and limited efficacy) is based on a poster abstract.
Quality Criteria Checklist: Review Articles
|1.||Will the answer if true, have a direct bearing on the health of patients?||Yes|
|2.||Is the outcome or topic something that patients/clients/population groups would care about?||Yes|
|3.||Is the problem addressed in the review one that is relevant to dietetics practice?||???|
|4.||Will the information, if true, require a change in practice?||???|
|1.||Was the question for the review clearly focused and appropriate?||???|
|2.||Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described?||???|
|3.||Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased?||???|
|4.||Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible?||???|
|5.||Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined?||???|
|6.||Was the outcome of interest clearly indicated? Were other potential harms and benefits considered?||???|
|7.||Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described?||???|
|8.||Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included?||Yes|
|9.||Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed?||???|
|10.||Was bias due to the review's funding or sponsorship unlikely?||???|