Rat ECG and general anesthesia: A chronobiological study

This investigation aimed to review the initial state of electrophysiological parameters that may predict the development of heart rhythm disorders in spontaneously-breathing pentobarbital-, ketamine-xylazine- and zoletil-anesthetized rats. These data will contribute to building a wider framework for a chronobiological perspective on the dependence of these parameters on the light-dark (LD) cycle under in vivo conditions. The study was performed using female Wistar rats, which were adapted to a 12 h LD cycle. Parameters evaluated included RR, PQ, QT, QTc intervals, the QRS complex and the amplitudes of P, R and T waves. The longest RR and QT interval duration occurred after the administration of ketamine-xylazine anesthesia in both the light period and the dark period. The longest PQ and QTc interval durations occurred under zoletil anesthesia in the light period. It is concluded that from a chronobiological perspective, the most significant electrophysiological myocardial susceptibility toward the potential risk for developing ventricular arrhythmias occurred under ketamine-xylazine anesthesia. The most important predisposition toward the development of ventricular arrhythmias related to disorders of impulse production and conduction was associated with zoletil anesthesia only in the light period. Ventricular arrhythmias resulting from disorders in the dispersion of refractory periods occurred under ketamine-xylazine anesthesia in both the lighted periods.