Evidence that carbon monoxide is a mediator of critical illness.

We have measured arterial carboxyhemoglobin levels as an indicator of endogenous carbon monoxide production in 32 consecutive admissions to our Surgical Intensive Care Unit. A severity of illness score (APACHE II) was determined for each patient at the same time that blood was drawn. An increase in the APACHE II score indicates a worsening of the patient's condition. There was a positive correlation between arterial carboxyhemoglobin levels and the APACHE II score (p < 0.005). An increase in the white blood cell count indicates an increase in the severity of illness. Carboxyhemoglobin levels correlated with an increase in the white blood cell count to greater than the normal maximum count of 10.5 x 10(3) cells/mm3 within a 24 hour period (p < 0.05). These findings support our hypothesis that endogenously produced carbon monoxide may play a role in the pathogenesis of critical illness.