Serial measurement of energy expenditure in critically ill patients - Feasibility and impact on nutrition provision.

Abstract

Background: Serial indirect calorimetry instead of prediction of energy expenditure is recommended in critically ill patients. However, the feasibility and the challenges associated with it are not systematically investigated. This prospective study was aimed to investigate the course of measured resting energy expenditure in critically ill adult medical patients, the challenges associated with it and factors that significantly impact variations in energy expenditure.

Method: Indirect calorimetry was serially performed on critically ill adult medical patients on invasive mechanical ventilation. Data on disease severity, body temperature, vasopressor support and sedation depth as well as nutrition therapy were also recorded.

Results: A total of 98 patients (65.3% males) with a mean age of 66.9±13.5 years were included. Their mean Acute Physiology And Chronic Health Evaluation-II score was 31.4± 8.4. There was a total of 600 potential measurement days, out of which indirect calorimetry could be carried out on 452 days (75.3%). There was a stepwise increase in resting energy expenditure during the first 7 days with a quasi-plateau on day 8 and beyond, amounting to an increase in resting energy expenditure by 19.0 ± 28.7%. Daily changes in body temperature and the Richmond Agitation and Sedation Scale showed a significant effect on variations in energy expenditure. The study patients received beginning from day 4 onwards 93.6±34.7% (95% confidence interval 86.1 - 101.1%) of their measured energy expenditure.

Conclusion: There is a stepwise increase in resting energy expenditure during the first week of critical care among critically ill adult medical patients. Patient-related factors and logistic challenges should be considered regarding indirect calorimetry. Body temperature and the degree of sedation have a significant impact on variations in energy expenditure.