Dynamic metabolic changes measured by indirect calorimetry during the early phase of septic shock: a prospective observational pilot study

BACKGROUND AND AIMS: Energy metabolism (energy deficit, substrate consumption) in the early phase of septic shock is not clearly understood. The objective of this study was to describe its evolution using indirect calorimetry. METHODS: Prospective observational pilot study including ventilated adult patients with septic shock admitted in a surgical intensive care unit (ICU). Metabolic data were collected using the COSMED Q-NRG + ® calorimeter: carbon dioxide production (VCO2), oxygen consumption (VO2), resting energy expenditure (REE), respiratory quotient (RQ) and the rate of substrate utilization (proteins, lipids, and carbohydrates). The main criterion was the evolution of the energy deficit (dE) from D1 to D6. RESULTS: In total, 34 patients were included and 15 patients (age: 57.6 ± 12.8 years; Simplified Acute Physiology Score II: 52 ± 11) were eligible for final analysis. Time for initiation of nutritional support was 2.5 ± 1.5 days. The dE improved during the study period (slope = 2.9 [1.8; 4.2]; p < 0.001). The REE remained stable during the first week with no significant variation (slope = −0.16 [−1.49; 0.79]; p = 0.78). The RQ remained stable overall (slope = 0.01 [0.00; 0.03]; p = 0.10). The substrates utilization significantly changed at D3 in favor of protein consumption (slope = 6.50 [4.44; 8.85]; p < 0.001) with an overall significant decrease in the consumption of non-protein substrates. CONCLUSION: Energy deficit improved while REE and RQ remained relatively stable during the first week of ICU stay. The significance of the variations of substrates consumption was unclear. These preliminary results should be further explored with larger studies.