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.