Changes in carbon dioxide production and oxygen uptake evaluated using indirect calorimetry in mechanically ventilated patients with sepsis

Background Several clinical guidelines recommend monitoring blood lactate levels and central venous oxygen saturation for hemodynamic management of patients with sepsis. We hypothesized that carbon dioxide production (VCO 2 ) and oxygen extraction (VO 2 ) evaluated using indirect calorimetry (IC) might provide additional information to understand the dynamic metabolic changes in sepsis. Methods Adult patients with sepsis who required mechanical ventilation in the intensive care unit (ICU) of our hospital between September 2019 and March 2020 were prospectively enrolled. Sepsis was diagnosed according to Sepsis-3. Continuous measurement of VCO 2 and VO 2 using IC for 2 h was conducted within 24 h after tracheal intubation, and the changes in VCO 2 and VO 2 over 2 h were calculated as the slopes by linear regression analysis. Furthermore, temporal lactate changes were evaluated. The primary outcome was 28-day survival. Results Thirty-four patients with sepsis were enrolled, 26 of whom survived 76%. Significant differences in the slope of VCO 2 (− 1.412 vs. − 0.446) ( p = 0.012) and VO 2 (− 2.098 vs. − 0.851) ( p = 0.023) changes were observed between non-survivors and survivors. Of note, all eight non-survivors and 17 of the 26 survivors showed negative slopes of VCO 2 and VO 2 changes. For these patients, 17 survivors had a median lactate of − 2.4% changes per hour (%/h), whereas non-survivors had a median lactate of 2.6%/hr ( p = 0.023). Conclusions The non-survivors in this study showed temporal decreases in both VCO 2 and VO 2 along with lactate elevation. Monitoring the temporal changes in VCO 2 and VO 2 along with blood lactate levels may be useful in predicting the prognosis of sepsis.