QT interval, defined as the time between the beginning of the QRS complex and the end of the T wave in electrocardiography (ECG), is an indicator of depolarization and repolarization of the myocardium.11 Prolongation of the heart rate corrected QT (QTc) interval reflects electrical instability of ventricles and is associated with life-threatening ventricular arrhythmias, including torsade de pointes, ventricular fibrillation and sudden cardiac death. Spinal anesthesia can cause profound prolongation of the QTc interval due to disparity between lumbar and thoracic sympathetic activity following subarachnoid block. Meanwhile inhalational anesthetics, sevoflurane, isoflurane, and desflurane are known to prolong QTc interval and intravenous anesthetics such as propofol, thiopental, etomidate and ketamin can also cause remarkable prolongation of the QTc interval. Moreover laryngoscopy and intubation may contribute to prolongation of the QTc interval because of the sympathetic stimulation. Over the years it has been occurred an increase in the proportion of elderly population requiring surgical anesthesia. The incidence of ventricular arrhythmias increases in advancing age even in the absence of underlying heart disease and elderly patients have reduced physiological functions and poor tolerance to anesthesia. However the choice of anesthesia type is critical in this population. To the best of knowledge, there was no published study to compare spinal anesthesia and inhalational anesthesia in elderly patients with regard to the QT interval changes. Investigators aimed to investigate the effects of spinal anesthesia on QT, QTc intervals and to compare general anesthesia with sevofluran in elderly patients.
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QTc interval
Timeframe: before anesthesia induction or spinal anesthesia; 1, 5 and 10 minutes after endotrakeal intubation or spinal anesthesia; after extubation or surgery