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The effects of propofol on rat transcranial magnetic motor evoked potentials
A S Fishback1, C B Shields, R D Linden
1Department of Neurological Surgery, University of Louisville, Kentucky, USA.
Abstract:
INTRAOPERATIVE MONITORING OF motor evoked potentials (MEPs) may become a valuable test of spinal cord function during surgery. Unfortunately, MEP responses are affected by most common anesthetics. We studied the effect of intravenous propofol on transcranial magnetic MEPs (tcMMEPs) in the rat. Baseline tcMMEPs were recorded before administration of the drug. Each rat then received three induction doses of propofol, 10, 5, and 5 mg/kg (totaling 10, 15, and 20 mg/kg) and three successive 20-minute infusion doses at rates of 10, 20, and 40 mg/kg/h, respectively. An MEP intensity series was performed after each induction dose, during each infusion, and during a 20-minute recovery period. tcMMEPs recorded during the induction period demonstrated a significant, dose-dependent increase in onset latency and a marked decrease in amplitude. Infusion tcMMEPs displayed increased onset latencies but demonstrated a significant change in amplitudes only after the largest infusion dose. The MEPs approached baseline levels after discontinuation of the propofol. This study demonstrates that tcMMEPs can be successfully recorded from the rat during propofol anesthesia.
Insights
Intravenous propofol anesthesia affects motor evoked potentials (MEPs) in rats, increasing latency and decreasing amplitude. However, transcranial magnetic motor evoked potentials (tcMMEPs) can still be recorded during propofol administration.
Area of Science:
- Neuroscience
- Anesthesiology
- Surgical Monitoring
Background:
- Intraoperative monitoring of motor evoked potentials (MEPs) is crucial for assessing spinal cord function during surgery.
- Common anesthetics, including propofol, can significantly alter MEP responses, posing challenges for real-time monitoring.
Purpose of the Study:
- To investigate the effects of intravenous propofol on transcranial magnetic motor evoked potentials (tcMMEPs) in a rat model.
- To determine the dose-dependent impact of propofol on tcMMEP parameters like latency and amplitude.
Main Methods:
- Rats underwent baseline tcMMEP recordings prior to propofol administration.
- Propofol was administered via induction doses and continuous infusions at escalating rates (10, 20, 40 mg/kg/h).
- tcMMEP intensity series were recorded after each dose, during infusions, and during recovery.
Main Results:
- Propofol significantly increased tcMMEP onset latency and decreased amplitude in a dose-dependent manner during induction.
- During infusion, onset latency increased, while amplitude changes were significant only at the highest dose.
- tcMMEPs returned to baseline levels after propofol discontinuation.
Conclusions:
- Transcranial magnetic motor evoked potentials (tcMMEPs) can be successfully recorded in rats under propofol anesthesia.
- Understanding propofol's effects on tcMMEPs is essential for accurate intraoperative spinal cord monitoring.