CHANGES IN THE T-WAVE AMPLITUDE OF ECG DURING ISOFLURANE ANESTHESIA

R/T amplitude ratio of electrocardiogram ECG), heart rate (HR) and sys tolic arterial pressure (SAP) were recorded in 15 patients awake, at 1 minimal alveolar concentration of isoflurane before and during surger y, and in deep anaesthesia (electroencephalogram burst suppression) du ring surgery. R/T-wave amplitude ratio and HR were sensitive to both s urgery and changes in the level of isoflurane anaesthesia; induction o f anaesthesia. skin incision and the rapid increase in the concentrati on of isoflurane all significantly decreased the T-wave amplitude, wit hout influence on the R-wave. Changes in the T-wave amplitude correlat ed directly to HR. SAP increased at skin incision and decreased when t he anaesthesia was deepened. The authors conclude that the R/T-wave am plitude ratio of ECG provides a reliable method for monitoring the sym pathetic tone during isoflurane anaesthesia.