• H Määttänen, R Anderson, J Uusijärvi, and J Jakobsson.
• Department of Orthopaedics, Sabbatsberg Hospital, Stockholm, Sweden.
• Acta Anaesthesiol Scand. 2002 Aug 1;46(7):882-6.

BackgroundThe auditory evoked potential (AEP) is sensitive to the depth of anesthesia. The A-line monitor is a novel device that processes the amplitude and latency of the AEP during the mid-latency time window to provide a simple numerical index, the AAItrade mark-index. The hypothesis of the present study was that titration of anesthetic depth (desflurane) by means of the AAItrade mark-index could decrease the consumption of the main anesthetic and shorten emergence times.MethodsThirty ASA I-II patients scheduled for elective open spine surgery under general anesthesia were randomly allocated to two groups. Group I (n=15), the main anesthetic, desflurane, was titrated with a target AAItrade mark-index of 20+/-5. Group II (n=15), desflurane was titrated according to routine clinical signs, including heart rate, blood pressure, sweating and tears. No fixed MAC-multiple was sought. The primary study variable was desflurane consumption; and secondary study variables were time to extubation and orientation.ResultsAll patients had an uncomplicated course and no patients showed signs of awareness or had any recall postoperatively. AAItrade mark-index guidance reduced desflurane consumption by 29% and improved emergence. Time until extubation and orientation and ability to state name and date of birth was significantly shortened among AAItrade mark-index titrated patients.ConclusionTitrating depth of desflurane anesthesia using AAItrade mark-index guidance decreased main anesthetic consumption and improved emergence during spine surgery.

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