ABSTRACT
BACKGROUND: Minimal flow anesthesia preserves the moisture content of CO2 absorbents and seems to be a factor inhibiting carbon monoxide generation. In order to assess the safety of minimal flow anesthesia, we studied carboxyhemoglobin (COHb) level in minimal flow anesthesia. METHODS: Forty women, ASA physical status I or II, undergoing total abdominal hysterectomy were randomly allocated to one of two groups with N2O-enflurane anesthesia. Anesthesia was maintained with O2 2 l/min and N2O 2 l/min (group 1) or O2 0.3 l/min and N2O 0.2 l/min (group 2). The arterial COHb levels were measured immediately after induction (T1), 45 min after induction (T2), 75 min after induction (T3), and after recovery from anesthesia (T4). RESULTS: Although there was no statistically significant change in both groups, the COHb level at T3 and T4 increased more than that at T1 in group 1, and that at T3 and T4 decreased more than that at T1 in group 2. There was a significant difference in the COHb level at T4 between group 1 (0.93 0.31%) and 2 (0.68 0.36%) (P <0.05). CONCLUSIONS: These results show that minimal flow anesthesia does not increase the COHb level and may be performed safely.