Sevoflurane requirements during ambulatory surgery:: a clinical study with and without AEP-index guidance

Background: Several monitors have been developed to measure anesthetic depth. The auditory evoked response uses an auditory signal to actively test the level of brain activity. The aim of the present study was to determine whether sevoflurane titration with A-line auditory guidance from the evoked potential monitor would reduce gas consumption and improve recovery times. Methods: Patients (n=60, aged 18-65years) undergoing elective knee arthroscopy were randomized to titrate the main anesthetic sevoflurane with O-2:N2O(1:2), either clinically (30 patients) or in combination with a target auditory evoked potential index of 30 5 (30 patients) using the A-line monitor (version 1.4, Danmeter A/S; Odense, Denmark). Induction was supplemented with fentanyl, and randomized to 0.05, 0.10 and 0.15mg immediately before propofol (10 in each group). Sevoflurane consumption and emergence times were the primary and secondary study end-points. Results: Guidance from the A-line monitor did not reduce the sevoflurane consumption time or the emergence, regardless of the fentanyl dose. However, it did reduce the time from the recovery room to discharge eligibility (P<0.05). Sevoflurane consumption decreased inversely with the fentanyl dose (P<0.01), with no impact on emergence times. Conclusion: The auditory evoked potential index provided by the A-line monitor does not decrease sevoflurane consumption or emergence times for ambulatory knee arthroscopy.