Retrospective evaluation of commonly used equations to predict energy expenditure in mechanically ventilated, critically ill patients.
OBJECTIVE
To determine which of four commonly used equations to estimate energy expenditure is precise and unbiased compared with energy expenditure as measured by indirect calorimetry.


METHODS
Retrospective, observational study.


METHODS
Adult medical intensive care unit in a research hospital of the National Institutes of Health Clinical Center.


METHODS
Seventy-six adult, mechanically ventilated, critically ill patients.


METHODS
Indirect calorimetry reports generated by the National Institutes of Health Critical Care Medicine Department's Metabolic Cart Consult Service were reviewed. Bias and precision of resting energy expenditure (REE) estimated by equations were computed using mean prediction error (ME) and root mean squared prediction error (MSE). Equations were considered precise if the 95% confidence interval for MSE was within 15% of the measured energy expenditure (MEE) determined by indirect calorimetry. Equations were considered unbiased if the 95% confidence interval for ME included zero. Paired t tests were used to compare estimated REE values for each predictive equation with MEE values determined by indirect calorimetry. Data were stratified into regions of bias using classification and regression tree analysis, as well as visual inspection of estimated REE-versus-MEE curves for each equation.


RESULTS
The Harris-Benedict equation multiplied by an activity factor of 1.2 was unbiased and precise. The Ireton-Jones equation was precise but biased. The American College of Chest Physicians' consensus recommendation was biased and imprecise. The Harris-Benedict equation without an activity factor also demonstrated bias and imprecision.


CONCLUSIONS
The Harris-Benedict equation multiplied by an activity factor of 1.2 is suitable for predicting REE and may be used in the absence of indirect calorimetry.
Alexander
Earnest
E
Department of Pharmacy Services, Tampa General Hospital, Tampa, Florida 33601-1289, USA. ealexander@tgh.org
Susla
Gregory M
GM
Burstein
Aaron H
AH
Brown
Dennis T
DT
Ognibene
Frederick P
FP
D000328:Adult; D000368:Aged; D002151:Calorimetry; D016638:Critical Illness; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012121:Respiration, Artificial; D012189:Retrospective Studies