Closed-Loop Target Controlled Infusion in Laparoscopic Cholecystectomy

Anesthetics alter electrocortical activity in a dose-dependent manner,and it is suggested that electroencephalographic(EEG)activity can provide a reliable basis for a surrogate measurement of hypnosis.An EEG monitor,the Narcotrend Index(NI),has proven useful to titrate hypnotic drugs.Because it is a single composite measure monitored continuously,it has been used in controlled studies to automatically guide propofol administration.Conversely,automated delivery systems for opioids have seldom been described using EEG activity There are no specific measures to quantify analgesia directly.Nevertheless,in the interaction between opioid-hypnotic synergy and loss of consciousness,when the dose of analgesic administered is sufficient to inhibit autonomic response to noxious stimuli,then the required hypnotic concentration is only that needed to achieve loss of consciousness.Moreover,a noxious stimulus such as laryngoscopy or periosteal pressure to the tibia may cause electrocortical activation with an increase in Narcotrend index,which indirectly reflects the analgesic state or the level of antinociception.Finally,an excitatory EEG arousal reaction resulting from nociceptive stimulation can provide a rational basis for analgesia administration.It can then be hypothesized that Narcotrend index could also be the controlled variable for opioid administration.