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

Abstract

Electrocardiographic (ECG) changes during microlaryngoscopy were studied with three methods of anaesthesia. In two main groups, balanced anaesthesia was induced by Althesin (=Althesin I group) in 98 patients or by thiopentone (=thiopentone group) in 68 patients. In 23 patients, halothane anaesthesia was induced by Althesin (=Althesin II group). During the procedure, the most common ECG changes in all groups were sinus tachycardia (54-78%), junctional rhythm (28-57%), ventricular ectopic beats (12-26%), T-wave changes (9-22%) and supraventricular ectopic beats (7-17%). There was no statistically significant difference in the total number of ECG changes between the groups. There was, however, significantly more sinus tachycardia in the Althesin II group (78%) than in the thiopentone group (54%). Junctional rhythm occurred significantly more often in the Althesin II group (57%) than in the Althesin I group (31%) or in the thiopentone group (28%). Upper junctional rhythm was most common in the Althesin I group, whereas middle junctional rhythm dominated in the Althesin II group. Ischaemic S-T segment depression did not occur in the thiopentone group, whereas in the Althesin I and II groups its incidence ranged from 6 to 13%. In all patients ECG changes disappeared without any special treatment after the manipulation of the vocal cords. The results suggest that there is no decisive difference in the occurrence of ECG changes between the three methods of anaesthesia.