ECG T-wave amplitude changes during thiopentone induction with or without alfentanil

The T-wave amplitude of ECG is thought to reflect the sympathetic tone of the heart but anaesthesia studies on this topic are rare. Haemodynamic and ECG T-wave amplitude changes were studied during induction of anaesthesia in 24 ASA I-II patients. Twelve patients were given alfentanil 30 μg kg-1 at induction while physiologic saline was given to the rest (control). Thiopentone was then administered at the rate of 5 mg s-1 until eyelash reflex disappeared. Vecuronium 0.1 mg kg-1 was given thereafter. No anticholinergics were used. The lungs were ventilated with 40% oxygen in air. Haemodynamic parametres and T-wave amplitude were measured before induction, before intubation, 30 s, 3 min and 5 min after intubation. A significandy higher amount of thiopentone was needed to abolish the eyelash reflex in the control group than in the alfentanil group (P<0.001). There were no changes in heart rate (HR) in the alfentanil group during the trial. Systolic and diastolic arterial pressures (SAP and DAP) were continuously below the preinduction levels in the alfentanil group. After baseline HR, SAP and DAP were significantly higher in the control group than in the alfentanil group at each data point. T-wave amplitude flattened significantly (P<0.001) after intubation in the control group while no significant changes were seen in the alfentanil group. T-wave flattening correlated to the increases in HR (P<0.01) and SAP (P<0.01). Three control patients with flattened T-wave had a transient bigeminia period after intubation. It is concluded that ECG T-wave amplitude flattening was associated with pressure and heart rate response to laryngoscopy and intubation. Alfentanil blunted these responses and prevented T-wave changes after intubation.