Electrocardiographic (ECG) changes were studied in 82 adult patients with a mean age of 49 years undergoing microlaryngoscopy. The patients were pretreated with practolol 0.15 mg/kg i. v. 5 min before induction of anaesthesia with thiopental. Anaesthesia was maintained with nitrous oxide in oxygen, fentanyl and suxamethonium‐infusion. ECG changes occurred in 49 of the patients before anaesthesia and procedure. Pre‐existing ECG changes increased or new changes occurred in 39 of the patients during intubation and in 38 during the procedure. The most common preanaesthetic ECG changes were flat or negative T‐wave (18), sinus tachycardia (13), ischaemic S‐T segment depression (8.5) and intraventricular conduction disturbance (8.5). ECG changes during intubation were sinus tachycardia (16), ventricular ectopic beats (12), supraventricular ectopic beats (10) and ischaemic S‐T segment depression (10). The most common changes during microlaryngoscopy were supraventricular ectopic beats (16), T‐wave flattening or inversion (15), ischaemic S‐T segment depression (11) and sinus bradycardia (10). In all patients ECG changes disappeared without any special treatment. Unlike our earlier identical study without practolol pretreatment, neither sinus tachycardia nor junctional rhythm occurred during microlaryngoscopy in the present study. The results suggest that practolol pretreatment before microlaryngoscopy is especially useful when sinus tachycardia and junctional rhythm shou
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