Effect of a single dose of esmolol on the bispectral index scale (BIS) during propofol/fentanyl anaesthesia

Background. Esmolol, a short-acting beta(1)-antagonist, can reduce anaesthetic requirements and decrease seizure activity during electroconvulsive therapy even after a single dose of 80 mg. We studied the effect of esmolol on the bispectral index scale (BIS), which is a processed EEG recently introduced to monitor depth of anaesthesia. Methods. We gave esmolol 80 mg to 30 healthy male patients after induction of anaesthesia using propofol, with either fentanyl (group 1) or placebo (group 2). Patients were ventilated mechanically through a laryngeal mask airway and anaesthesia was maintained using propofol to keep the BIS value between 55 and 60. Results. Esmolol did not affect the BIS index value in either group. In group 1, the areas (mean (sd)) under the BIS vs time curve 3 min before and 3 min after esmolol administration were 145 (9) and 146 (8) respectively (P=0.116). In group 2 values were 147 (8) and 146 (7) respectively (P=0.344). In contrast, in group 1 the area under the systolic arterial pressure (SAP) curve was 299 (31) before and 270 (29) after esmolol (P<0.001), and 156 (17) and 141 (17) respectively for heart rate (P<0.001). In group 2 values were 326 (36) and 302 (41) for SAP (P<0.001) and 182 (25) and 155 (22) for heart rate (P<0.001). Conclusions. The results suggest that a single dose of esmolol affects the SAP and heart rate but does not affect BIS values.