Continuous Indirect Calorimetry in Critically Injured Patients Reveals Significant Daily Variability and Delayed,
Georgia Vasileiou1, Michelle B Mulder1, Sinong Qian1
1Miller School of Medicine, DeWitt Daughtry Family Department of Surgery, University of Miami, Miami, Florida, USA.
Background:
Previous studies have used using Indirect Calorimetry (IC) with solitary or sparse measurements of resting energy expenditure (REE). This "snapshot" may not capture the dynamic nature of metabolic requirements. Using continuous IC, we describe the variation of REE during the first days in the intensive care unit.
Methods:
Injured adults (≥18 years) requiring mechanical ventilation from March 2018 to September 2018 were enrolled. IC was initiated within 4 days of admission and continuous REE recorded until 14 days, extubation, or death. Multiple 10-minute periods collected during steady state were used to calculate daily REE maximum, minimum, average, and variability [(REEmax - REEmin/2)/average REE].
Results:
We included 55 patients. Median age was 38 [27-58] years, 38 (69%) were male, body mass index was 28 [25-33] kg/m2 , and Acute Physiology and Chronic Health Evaluation II was 17 [14-24]. Mechanism of injury was: blunt (n = 38, 69%), penetrating (n = 9, 16%), and burn (n = 8, 15%). Average REE increased gradually from 1,663 kcal [1,435-2,143] to a maximum of 2,080 [1,701-2,336] on day 7, a relative 25% increase, which was sustained through day 14. REE variability ranged 8%-13% and was not reliably predicted by fever, tachycardia, elevated intracranial pressures, hypertension, or hypotension.
Conclusion:
In critically injured patients, steady-state REE measurements display fluctuations over a 24-hour period and demonstrate a gradual rise over the first few days after injury. Continuous REE, if available, is recommended for more precise matching of energy delivery to metabolic requirements.
