• T Kurita, K Takata, K Morita, and S Sato.
• Department of Anesthesiology and Intensive Care, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan. tadkur@hama-med.ac.jp
• Br J Anaesth. 2008 Jun 1; 100 (6): 841-5.

BackgroundWe have previously reported that landiolol, an ultra-short-acting beta1-adrenoceptor antagonist, does not alter the anaesthetic effects of isoflurane. Here, we investigated the influence of propranolol on the electroencephalographic (EEG) effects and minimum alveolar concentration (MAC) of isoflurane.MethodsFourteen swine [25.0 (SD 4.0) kg] were anaesthetized by isoflurane inhalation. The inhalation concentration was decreased to 0.5% and maintained for 25 min, before being returned to 2%, and maintained for a further 25 min. End-tidal isoflurane concentrations and spectral edge frequencies were recorded. Pharmacodynamic analysis was performed using a sigmoidal inhibitory maximal effect model for spectral edge frequency vs effect-site concentration. After measurement of the EEG effect, MAC was determined using the dew-claw clamp technique, in which movement in response to clamping is recorded. After completion of control measurements, a propranolol 4 mg bolus followed by an infusion (2 mg h(-1)) was started. After a 30 min stabilization period, the inhalation concentration of isoflurane was varied as in the control period and MAC was re-assessed.ResultsPropranolol shifted the concentration-effect relationship to the left and decreased the effect-site concentration that produced 50% of the maximal effect from 1.30 (0.18) to 1.13 (0.17)%. Propranolol also decreased isoflurane MAC from 1.91 (0.35) to 1.54 (0.32)%.ConclusionsPropranolol alters both the hypnotic and anti-nociceptive effects of isoflurane. In contrast to landiolol, lipophilic beta-adrenoceptor antagonists may increase the potency of inhalational anaesthetics.

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