Modification of the haemodynamic responses to induction of anaesthesia and tracheal intubation with alfentanil, esmolol and their combination.

The purpose of this double-blind randomized work was to study the effect of alfentanil and esmolol and their half-dose combination on the increases of heart rate and arterial pressure and on the prolongation of the QTc interval of the ECG occurring during anaesthetic induction. Sixty ASA class I-II patient with mean age ranging from 26 to 32 yr among the groups. Patients were allocated to one of four equal groups to receive saline, esmolol 2 mg.kg-1, alfentanil 0.03 mg.kg-1 and alfentanil 0.015 mg.kg-1+esmolol 1 mg.kg-1. Anaesthesia was induced with thiopentone. Succinylcholine was used to facilitate tracheal intubation. Haemodynamic variables were measured non-invasively and the QTc interval with the aid of a microcomputer. Comparisons between the groups were performed using two-way analysis of variance with repeated measures. Both alfentanil and alfentanil-esmolol prevented the increase of heart rate and arterial pressure caused by intubation whereas esmolol prevented only the increase of the heart rate. None of the treatments prevented prolongation of the QTc interval after intubation and only alfentanil prevented that after succinylcholine. The present results suggest that in the prevention of the haemodynamic responses to tracheal intubation, the half-dose combination of alfentanil and esmolol is as effective as alfentanil and superior to esmolol. The combination is preferable to relatively large doses of either drug in circumstances where side effects, such as respiratory depression due to alfentanil or bradycardia due to both drugs should be minimized.