Increased endogenous carbon monoxide production in severe sepsis

Objective: A comparison was made between the endogenous carbon monoxide (CO) production in mechanically ventilated critically ill adult patients with, and those without, severe sepsis. Design: Prospective comparative study. Setting: Medical ICU in a community hospital. Patients: Twenty-four patients with severe sepsis of various etiologies and five control patients with varying diagnoses. Intervention: CO concentration was determined with an infrared CO analyzer on exhaled breath collected at the outlet of the ventilator. Endogenous CO production was estimated by the lung CO excretion rate measured at steady state. Measurements and main results: Endogenous CO production was higher in the sepsis group during the first 3 days of treatment in comparison to the control group (10.9 +/- 5 (SD) mul/kg per h on day 1, 7.8 +/- 4.9 mul/kg per h on day 2 and 6.9 +/- 4.7 mul/kg per h on day 3 versus 2.1 +/- 0.5 mul/kg per h; p<0.01 for each comparison). Survivors of sepsis had a significantly higher endogenous CO production on day I compared to non-survivors (14.7 +/- 5.3 versus 8.5 +/- 3.3 μl/kg per h; p=0.02). Conclusion: Endogenous CO production was significantly higher in mechanically ventilated patients suffering from severe sepsis. Further studies are required in order to determine the mechanism(s) and the functional significance of this increase.