Background : Oxidative stress conditions may be responsible for an up-regulation of the expression of heme oxygenase, the enzyme synthesizing carbon monoxide (CO) in cells. Elevated levels of arterial carboxyhemoglogin (CO-Hb) have been found in critically ill patients, including those suffering from acute lung injury. We aimed to investigate the changes of arterial CO-Hb levels in COVID-19 critically ill patients.
Methods : A retrospective cohort study was conducted on the medical charts of 63 patients admitted in the ICU for severe COVID-19 infection over the period March 1 – May 31, 2020.
Results : The overall ICU mortality rate was 39%. Non-survivors had a significantly higher profile of arterial CO-Hb levels than survivors (p<0.001), but arterial CO-Hb increased significantly from admission to day 30 in both groups (p<0.001). Mortality could not be predicted by the changes in arterial CO-Hb, but there was a correlation between the maximal arterial CO-Hb value and SOFA score on admission. No correlation could be demonstrated between arterial CO-Hb and serum C-reactive protein (CRP) as a marker of the inflammatory response.
Conclusions : A greater increase of arterial CO-Hb levels over time may represent another marker of severity of COVID-19 infection in ICU patients.