[Isorhythmic dissociation during sevoflurane anesthesia]

Arrhythmia during general anesthesia occurrs occasionally as a result of the effect of inhalation anesthetic agent on cardiac conduction. We experienced a case of atrioventricular junctional rhythm (AVJR) during maintenance of general anesthesia with sevoflurane. A 61-year-old woman with normal preoperative electrocardiogram was scheduled for right total knee arthroplasty and autologous iliac crest bone graft under general and epidural anesthesia. After inserting the lumbar epidural catheter, endotracheal intubation was performed following anesthesia induction with fentanyl, thiopental, and vecuronium, and anesthesia was maintained using inhalation of nitrous oxide and sevoflurane, and epidural anesthesia with ropivacaine. Forty minutes after starting operation, the dissociated and upright P-wave approached the QRS complex, remaining within QRS complex for several beats, and then reappeared from it electrocardiographically. ST segment was transiently depressed from baseline. The R-R interval and waveform of the QRS complex did not change. The sequence was repeated. The blood pressure had been held slightly depressed but waveform of pulse oxymetry (SpO2) did not change during this phenomenon. We diagnosed it as AVJR, which is classified into isorhythmic dissociation. After discontinuation of sevoflurane at the end of the operation, isorhythmic dissociation returned to sinus rhythm. Sevoflurane could induce atrioventricular conduction disturbance leading to isorhythmic dissociation of AVJR. We should be aware that hypotension can result from isorhythmic dissociation during sevoflurane anesthesia.