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Effect of isoflurane (Forane) on intraoperative electrocorticogram
M E Fiol1, J A Boening, R Cruz-Rodriguez
1MINCEP Epilepsy Care, Minnesota Comprehensive Epilepsy Program, Minneapolis, Minnesota.
Epilepsia
|September 1, 1993
Summary
Isoflurane anesthesia at concentrations up to 1.25% does not significantly alter electrocorticogram (ECoG) spike activity during epilepsy surgery. This finding suggests isoflurane is safe for monitoring brain activity before burst suppression occurs.
Area of Science:
- Anesthesiology
- Neuroscience
- Epilepsy Surgery
Background:
- Isoflurane is a common inhalation anesthetic used during craniotomy.
- Previous reports suggest isoflurane may suppress electrocorticogram (ECoG) spike activity.
- Understanding isoflurane's effect on ECoG is crucial for epilepsy surgery.
Purpose of the Study:
- To investigate the impact of varying isoflurane concentrations on spike burst activity during intraoperative ECoG.
- To determine if isoflurane affects ECoG spike counts within a specific concentration range relevant to epilepsy surgery.
Main Methods:
- Fifteen patients undergoing epilepsy surgery with ECoG monitoring were studied.
- Isoflurane concentrations ranged from 0.25% to 1.25%.
- Spike bursts were counted in 5-min epochs, with controlled nitrous oxide, CO2, and alfentanil levels.
Main Results:
- Median spike counts showed no significant difference across isoflurane concentrations (0.25% to 1.25%).
- The number of spikes remained relatively stable, even at 1.25% in some patients before burst suppression.
- No statistically significant effect of isoflurane on spike activity was observed.
Conclusions:
- Isoflurane, within the tested range (0.25-1.25%), does not significantly affect ECoG spike activity in epilepsy surgery patients.
- Maintaining isoflurane below the burst suppression threshold is key.
- These findings support the use of isoflurane for anesthesia while monitoring ECoG in epilepsy surgery.