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Midlatency auditory evoked potentials during anaesthesia with increasing endexpiratory concentrations of desflurane
D Schwender1, S Klasing, P Conzen
1Institute for Anaesthesiology, University of Munich, Germany.
Background:
Under general anaesthesia with the volatile anaesthetics halothane, enflurane and isoflurane, midlatency auditory evoked potentials (MLAEP) are suppressed dose-dependently. Therefore, MLAEP have been used to measure depth of anaesthesia and to indicate intraoperative awareness. Desflurane is a new volatile anaesthetic and its effect on MLAEP have not been studied previously.
Methods:
We have studied MLAEP during general anaesthesia with increasing endexpiratory concentrations of desflurane in 12 patients scheduled for elective gynaecological surgery. Auditory evoked potentials were recorded in the awake state and during anaesthesia with endexpiratory steady state concentrations of 1.5, 3.0, 4.5 and 6.0 vol % of desflurane on vertex (positive) and mastoids on both sides (negative). Latencies of the peaks V, Na, Pa, Nb, Pl (ms) and amplitudes Na/Pa, Pa/Nb and Nb/Pl (micro V) were measured.
Results:
In the awake state, MLAEP had high peak-to-peak amplitudes and a periodic waveform. During general anaesthesia with increasing endexpiratory concentration of desflurane, the latency of the brainstem response V increased only slightly. In contrast, MLAEP showed a marked dose-dependent and statistically significant increase in latencies of Na, Pa, Nb and Pl and decrease in amplitudes of Na/Pa, Pa/Nb and Nb/Pl. Under 6.0 vol % of desflurane MLAEP were severely attenuated or even abolished.
Conclusion:
Based on these observations, endexpiratory concentrations of > or = 4.5 vol % desflurane should suppress awareness phenomena such as auditory perceptions during anaesthesia.
Insights
This study investigated how desflurane anesthesia affects midlatency auditory evoked potentials (MLAEP). High concentrations of desflurane significantly suppressed MLAEP, suggesting it may prevent intraoperative awareness.
Area of Science:
- Anesthesiology
- Neurophysiology
Background:
- Midlatency auditory evoked potentials (MLAEP) are suppressed by volatile anesthetics like halothane, enflurane, and isoflurane.
- MLAEP are used to monitor anesthesia depth and detect intraoperative awareness.
- The effect of the new volatile anesthetic desflurane on MLAEP was previously unstudied.
Purpose of the Study:
- To investigate the dose-dependent effects of desflurane on MLAEP.
- To determine if desflurane suppresses MLAEP in a manner similar to other volatile anesthetics.
Main Methods:
- MLAEP were recorded in 12 patients undergoing gynecological surgery.
- Measurements were taken during anesthesia with increasing end-expiratory desflurane concentrations (1.5, 3.0, 4.5, 6.0 vol%).
- Latencies and amplitudes of specific MLAEP peaks (V, Na, Pa, Nb, Pl) were analyzed.
Main Results:
- A slight increase in brainstem response V latency was observed.
- Significant, dose-dependent increases in Na, Pa, Nb, and Pl latencies occurred with rising desflurane concentrations.
- MLAEP amplitudes (Na/Pa, Pa/Nb, Nb/Pl) decreased significantly and were severely attenuated or abolished at 6.0 vol% desflurane.
Conclusions:
- Desflurane exhibits a dose-dependent suppressive effect on MLAEP.
- End-expiratory desflurane concentrations of 4.5 vol% or higher are likely sufficient to suppress auditory awareness during anesthesia.