Preservation of neurogenic motor-evoked potentials during isoflurane electroencephalographic burst suppression in rats.
METHODS
A prospective laboratory study was performed in a rat model.


OBJECTIVE
To test the hypothesis that neurogenic motor-evoked potentials are more resistant to suppressive changes from the volatile anesthetic isoflurane than cortically recorded somatosensory-evoked potentials and electroencephalography.


BACKGROUND
Techniques for monitoring spinal cord motor tracts have been developed because sensory tract monitoring with somatosensory-evoked potentials is at times inadequate. Potentials from transcranial magnetic and electrical stimulation are very sensitive to anesthesia. Neurogenic motor-evoked potentials are thought to be more resistant.


METHODS
Eight mature Sprague-Dawley rats were studied during isoflurane general anesthesia. Two-channel raw and computer-processed electroencephalograms, somatosensory-evoked potentials, and neurogenic motor-evoked potentials were recorded at six levels of anesthetic depths.


RESULTS
Neurogenic motor-evoked potential amplitudes and latencies were unaltered. The electroencephalograms were depressed to isoelectricity with periodic burst activity above 1.27% isoflurane. Processed electroencephalograms showed depression above 0.72%. The somatosensory-evoked potentials were suppressed by increasing isoflurane and were not discernible at 2.2%.


CONCLUSIONS
Neurogenic motor-evoked potential signals are well preserved in rats during exposure to isoflurane concentrations that eliminate somatosensory-evoked potential waveforms and depress electroencephalograms to burst suppression.
Russell
G B
GB
Department of Anesthesia, Penn State University College of Medicine, Hershey.
Schwentker
M C
MC
Graybeal
J M
JM
D000818:Animals; D004569:Electroencephalography; D005071:Evoked Potentials / Q000187:drug effects* / Q000502:physiology; D007530:Isoflurane / Q000494:pharmacology*; D011446:Prospective Studies; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000187:drug effects* / Q000502:physiology
D007530:Isoflurane