Abstract
Automated anesthesia systems that continuously monitor cortical excitability (CE) changes to govern drug infusion rates, are desirable. Paired‐pulse transcranial magnetic stimulation (ppTMS), with electromyography (EMG), provides noninvasive CE measures. We tested whether, and with what temporal resolution, ppTMS‐EMG detects dose‐dependent CE in rats anesthetized with continuous intravenous propofol. Motor‐evoked potentials (MEPs) were recorded every 20 seconds as either propofol bolus or change in infusion rate was applied. ppTMS‐derived measures varied in direct proportion to propofol dose with subminute temporal resolution. We conclude that ppTMS‐EMG enables real‐time markers of target engagement by anesthetics that may be incorporated into an automated device.
Highlights
Transcranial magnetic stimulation (TMS) is a well-tolerated, noninvasive method for focal cortical stimulation,1 where small intracranial electrical currents are induced by a powerful and fluctuating extracranial magnetic field
Annals of Clinical and Translational Neurology published by Wiley Periodicals, Inc on behalf of American Neurological Association
In rats that received a bolus of 10 mg/kg, the effect lasted for ~5 min before trending toward recovery to baseline
Summary
Transcranial magnetic stimulation (TMS) is a well-tolerated, noninvasive method for focal cortical stimulation, where small intracranial electrical currents are induced by a powerful and fluctuating extracranial magnetic field. Paired-pulse TMS (ppTMS) involves delivering a conditioning stimulus pulse (CS) followed by a test stimulus (TS) after a predetermined interstimulus interval (ISI) to modulate inhibitory or excitatory circuits. A subset of ppTMS protocols, long interval ppTMS (LI-ppTMS) in rats, as in humans, activate intracortical inhibitory circuits and can detect changes in longinterval intracortical inhibition (LICI) pursuant to pharmacologic intervention or injury.. Annals of Clinical and Translational Neurology published by Wiley Periodicals, Inc on behalf of American Neurological Association.
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