[Case report of paradoxical arousal-like EEG changes during pediatric laparotomy]

An 8-year-old boy with Chiari malformation and myelomeningocele received total cystectomy and ileal neobladder surgery under general anesthesia with sevoflurane, nitrous oxide, and intravenous fentanyl. Bispectral index (BIS) suddenly decreased from 50 to 7 with large slow delta waves during ileal anastomosis, although there was no change regarding blood pressure and heart rate. This EEG change was considered first as 'paradoxical arousal', of which mechanism is commonly due to the unexpected noxious stimulation. In spite of additional intravenous fentanyl, this EEG pattern did not change at all, but disappeared spontaneously. This episode repeated two times under the similar condition during surgery. The patient recovered from anesthesia without any neurological complications. The effect-site fentanyl concentration simulated later was supposed to suppress the noxious stimulation adequately during this procedure. Although we can not elucidate the mechanism of paradoxical arousal-like EEG change, our case report suggests that paradoxical arousal may occur by factors other than inadequate anesthesia.