Carboxyhemoglobin changes in relation to inspired oxygen fraction during general anesthesia

Abstract

Measurement of carboxyhemoglobin could be a new method for evaluation of the severity of inflammatory airway disease, acute organ dysfunction, or stress by surgery and anesthesia. To use this measurement during mechanical ventilation, it is important to clarify the effects of factors that interfere with carboxy- hemoglobin levels. The aim of our study was to investigate the preoperative changes of carboxyhemoglobin to inspired oxygen fraction during general anesthesia and mechanical ventilation. Our second aim was to evaluate the effect of preoxygenation on the level of carboxyhemo- globin. Methods: The study included 30 patients scheduled for urologic surgery under general endotracheal anesthesia, aged 18-60 years, divided into two groups. The study group comprised patients who were smoking cigarettes or tobacco pipe, while the control group included non-smokers. In both groups carboxyhemoglobin levels were determined preoperatively, after preoxygenation, and one hour after induction in anesthesia. Results: carboxyhemoglobin levels were decreased after preoxygenation in both groups. One hour after induction in anesthesia under mechanical ventilation with inhaled fraction of a mixture of O2 (50%) and air (50%) the average values of carboxyhemoglobin between the two groups were different. The average values of carboxyhemoglobin between the two groups in all three time points were statistically significantly different (p=0.00). Conclusion: Changes in carboxyhemoglobin concentrations in arterial blood occur during general anesthesia and mechanical ventilation, although these amplitudes are small when compared to carbon monoxide intoxication. It is likely that organ perfusion and functions are affected by these monoxide gas mediators during surgery.

Keywords

• carboxyhemoglobin
• inspired oxygen fraction
• general anesthesia