BACKGROUND: The increased oxidative stress resulting from the inflammatory 
responses in sepsis initiates changes in mitochondrial function which may result 
in organ damage, the most common cause of death in the intensive care unit 
(ICU). Deficiency of coenzyme Q10 (CoQ10), a key cofactor in the mitochondrial 
respiratory chain, could potentially disturb mitochondrial bioenergetics and 
oxidative stress, and may serve as a biomarker of mitochondrial dysfunction. 
Hence, we aimed to investigate in initially non-septic patients whether CoQ10 
levels are decreased in sepsis and septic shock compared to ICU admission, and 
to evaluate its associations with severity scores, inflammatory biomarkers, and 
ICU outcomes.
METHODS: Observational retrospective analysis on 86 mechanically-ventilated, 
initially non-septic, ICU patients. CoQ10 was sequentially measured on ICU 
admission, sepsis, septic shock or at ICU discharge. CoQ10 was additionally 
measured in 25 healthy controls. Inflammatory biomarkers were determined at 
baseline and sepsis.
RESULTS: On admission, ICU patients who developed sepsis had lower CoQ10 levels 
compared to healthy controls (0.89 vs. 1.04 µg/ml, p < 0.05), while at sepsis 
and septic shock CoQ10 levels decreased further (0.63 µg/ml; p < 0.001 and 0.42 
µg/ml; p < 0.0001, respectively, from admission). In ICU patients who did not 
develop sepsis, admission CoQ10 levels were also lower than healthy subjects 
(0.81 µg/ml; p < 0.001) and were maintained at the same levels until discharge.
CONCLUSION: CoQ10 levels in critically-ill patients are low on ICU admission 
compared to healthy controls and exhibit a further decrease in sepsis and septic 
shock. These results suggest that sepsis severity leads to CoQ10 depletion.