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. Haemodyn amic and ECG T-wave amplitude changes were studied during induction of anaesthesia in 24 ASA I-II patients. Twelve patients were given alfen tanil 30 mu g kg(-1) at induction while physiologic saline was given t o the rest (control). Thiopentone was then administered al 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 v entilated with 40% oxygen in air. Haemodynamic parametres and T-wave a mplitude were measured before induction, before intubation, 30 s, 3 mi n and 5 min after intubation. A significantly higher amount of thiopen tone was needed to abolish the eyelash reflex in the control group tha n in the alfentanil group (P<0.001). There were no changes in heart ra te (HR) in the alfentanii group during the trial. Systolic and diastol ic arterial pressures (SAP and DAP) were continuously below the preind uction levels in the alfentanil group. After baseline HR, SAP and DAP were significantly higher in the control group than in the alfentanii group at each data point. T-wave amplitude flattened significantly (P< 0.001) after intubation in the control group while no significant chan ges 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 intubati on. It is concluded that ECG T-wave amplitude flattening was associate d with pressure and heart rate response to laryngoscopy and intubation . Alfentanil blunted these responses and prevented T-wave changes afte r intubation.