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Auditory evoked response during propofol anaesthesia after pre-induction with midazolam
M D Brunner1, M R Nel, R Fernandes
1Department of Anaesthetics and Intensive Care, Division of Surgery, Anaesthetics and Intensive Care, Faculty of Medicine, Imperial College, Northwick Park Hospital, Watford Road, Harrow, Middlesex HA1 3UJ, UK.
British Journal of Anaesthesia
|October 16, 2002
Summary
Pre-anesthesia midazolam significantly reduced the required propofol dose and time to loss of consciousness (LOC). Auditory evoked responses reflect anesthetic depth, not drug plasma concentrations.
Area of Science:
- Anesthesiology
- Pharmacology
- Neuroscience
Background:
- Midazolam is known to reduce propofol dosage in clinical anesthesia.
- This study investigated the specific effects of pre-anesthetic midazolam on propofol requirements and induction time.
Purpose of the Study:
- To quantify the reduction in propofol dose needed for loss of consciousness (LOC) when midazolam is administered prior to anesthesia.
- To determine the effect of midazolam pre-treatment on the time required to achieve LOC.
- To evaluate the utility of auditory evoked responses (AER) in reflecting anesthetic depth.
Main Methods:
- A comparative study involving 20 patients receiving midazolam before anesthesia and 20 control patients.
- Auditory evoked responses (AER) were monitored to assess anesthetic depth.
- Loss of consciousness (LOC) was defined by loss of response to verbal command and eyelash reflex.
Main Results:
- LOC was achieved significantly faster in the midazolam group (75 s) compared to the control group (113 s).
- The required propofol dose for LOC was substantially lower in the midazolam group (1.3 mg kg-1) versus the control group (2.3 mg kg-1).
- While Pa amplitude and Nb latency showed trends, AER changes did not significantly differ between groups post-LOC.
Conclusions:
- Co-induction with midazolam and propofol effectively reduces propofol requirements.
- Auditory evoked responses (AER) serve as a reliable indicator of anesthetic depth, independent of plasma drug concentrations.