Comparison of electrocardiographic changes during microlaryngoscopy under halothane anaesthesia induced by althesin or thiopentone.

The incidences of electrocardiographic (ECG) changes during microlaryngoscopy under halothane anaesthesia were compared by using Althesin and thiopentone as induction agents. During the procedure the most common ECG change in both groups was junctional rhythm, which occurred in 37% of the patients in the Althesin group and in 29% of the patients in the thiopentone group. The next most common changes in the Althesin group were: ventricular ectopic beats (22%), ischaemic S-T segment depression (14%), and T wave flattening or inversion (14%); those in the thiopentone group were ventricular ectopic beats (18%) and rapidly ascending S-T segment depression (12%). As well as during the procedures, some ECG changes were registered in both groups during intubation. ECG changes disappeared without any special treatment after manipulation of the vocal cords or after intubation. There was no statistically significant difference in the total incidence of dysrhythmias between the Althesin and thiopentone groups, but the types of dysrhythmias were different in the two groups. There were more lower nodal rhythms, less serious ectopic beats and more ischaemic S-T segment depression in the Althesin group than in the thiopentone group. The results suggest that Althesin is useful and superior to thiopentone in patients with a tendency to develop serious ventricular ectopic beats, whereas in patients with heart and coronary arterial disease, Althesin is inferior to thiopentone and should be used with care.