Effects of AAI Monitoring on Anesthetic Requirement and Recovery Profiles in Obese Patients.

Introduction: The auditory evoked potentials (AEP) provide a dynamic measure of active brain response to a stimulus that can index the depth of anesthesia. The A-line AEP monitor expresses the amplitude and the latency of mid-latency evoked potentials as a the simple A-line ARX index (AAI). Aim of this study was to evaluate the impact of AAI monitoring on postanesthetic recovery in obeses. Methods: Sixty consecutive obese patients were randomly assigned to undergo LGB under monitoring of sevoflurane anesthesia by either standard clinical parameters (SCP) or by AAI. All patients had monitored heart rate, arterial blood pressure, inspiratory and expiratory end-tidal gas concentrations and AAI before induction of anesthesia, every 5 min during anesthesia and 10 min in postanesthesia. AEP were generated and recorded with the A-line AEP monitor (Alaris medical system, Hampshire, UK). All drugs were given based on ideal body weight and their total dosage was recorded. Consomption of sevoflurane was calculated using an equation (consumption = delivered concentration ´ fresh gas flow ´ time sevoflurane administration ´ molecular weight/2.412 ´ density of sevoflurane). AAI made known only to the anesthesiologists taking care of AAI monitored patients. Anesthesia was induced with intravenous propofol 2–3 mg/kg and fentanyl 1–2 µg/kg. Anesthesia was maintained with sevoflurane given initially at 1 MAC (about 2.2%, gas flow of 2 l/min) and then adjusted to maintain heart rate and blood pressure within 20% variation from baseline in the SCP group and the AAI index between 15 and 25 in the AAI group. Additional 1 µg/kg fentanyl was given to the SCP patients when hemodynamic changes could not be controlled within 5 min by sequential 0.5% increases in end-tidal sevoflurane concentrations and to the AAI group when hemodynamic parameters were higher than 20% from baseline and AAI values below 15. Sevoflurane was discontinued at the end of skin suture. After extubation oxygen was delivered intermittently at 5 l/min to maintain SpO2 above 90% and VAS for nausea and pain was recorded every 10 min. Results: No difference was observed between groups in anesthesia and surgery times, consumption of sevoflurane and VAS scores of nausea and pain. In comparison to the SCP monitored patients, however, the AAI monitored patients had significantly lower mean values of AAI and of end tidal sevoflurane during anesthesia and significantly shorter times to eye opening and to extubation and times of oxygen supplementation during postanesthesia.[table1]Discussion: In this study, AAI guided anesthesia results in a faster recovery of consciousness and of respiratory functions in obese patients. Discussion: AAI guided anesthesia results in a faster recovery of consciousness and of respiratory functions in obese patients.