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Sevoflurane anaesthesia was conducted using a totally closed circuit PhysioFlex anaesthesia machine (PhysioFlex group) or with a standard Modulus CD anaesthesia machine (Modulus group) (n = 8 in each group). The PhysioFlex was used under closed system conditions and the Modulus was used under low-flow system conditions (flow rate 1 litre min-1). Concentrations of sevoflurane degradation products and the temperature of soda lime were compared. Degradation products in the circuit were measured hourly, and the temperature of soda lime was monitored. The only degradation product detected was CF2 = C(CF3)-O-CH2F (compound A). Maximum concentrations of compound A were significantly lower (median 8.5 (range 5.4-15.9) ppm) in the PhysioFlex than in the Modulus group (21.2 (16.5-27.4) ppm) (P < 0.05). The maximum temperature of soda lime was also significantly lower in the PhysioFlex group (35.3 (32.1-36.3) degrees C vs 44.6 (43.0-47.1) degrees C, respectively) (P < 0.05). Hourly compound A concentrations were lower in the PhysioFlex group than in the Modulus group. End-tidal sevoflurane concentrations during measurement of degradation products were not different between groups. Therefore, use of the totally closed PhysioFlex system may significantly reduce compound A concentrations compared with low-flow anaesthesia using a standard anaesthesia machine.

Background. β-Adrenergic blocking agents may interact with anaesthetics, and several studies suggest that β-blockers attenuate electroencephalographic responses during general anaesthesia. We have investigated the influence of landiolol, an ultra-short-acting beta 1-adrenoceptor antagonist, on the electroencephalographic effect of isoflurane in pigs. Methods. Ten swine were anaesthetized through inhalation of 2% isoflurane. The inhalational concentration was then decreased to 0.5% and maintained for 25 min, before being returned to 2% and maintained for a further 25 min (control period). After control measurements, infusion of landiolol (at 0.125 mg kg−1 min−1 for 1 min, and then at 0.04 mg kg−1 min−1) was started. After a 20 min stabilization period, the inhalational concentration was varied as in the control period (40 γ landiolol). Finally, infusion of landiolol was increased from 0.04 to 0.2 mg kg−1 min−1, and after a 20 min stabilization period, the inhalational concentration was again varied as in the control period (200 γ landiolol). End-tidal isoflurane concentrations and spectral edge frequencies were recorded throughout the study. Analysis of the pharmacodynamics was performed using a sigmoidal inhibitory maximal effect model for spectral edge frequency vs effect-site concentration. Results. There were no significant differences in the effect of isoflurane among the conditions used. Landiolol did not shift the concentration–effect relationship [the effect-site concentration that produced 50% of the maximal effect was 1.35 (0.17)% under control conditions, 1.30 (0.12)% at 40 γ landiolol, and 1.38 (0.30)% at 200 γ landiolol]. Conclusion. Landiolol does not alter the electroencephalographic effect of isoflurane.