Inhalation and intravenous anesthetics possess both proconvulsant and anticonvulsant properties. The mechanisms of these contrasting neural effects are not fully understood. Biological differences in responses, bioavailability, effect on excitatory and inhibitory neurons, and these neurons' responses to the agents may result from delivery of varying concentrations or doses. With deepening levels of anesthesia, characteristic EEG changes occur (see Table: Anesthetic Drugs and the EEG):

  1. increased beta activity
  2. progressive slowing of the background
  3. a flat-line or burst-suppression record

Postoperatively, EEG slowing often persists for several days or, occasionally, for several weeks.

As general anesthetics, all halogenated inhalational agents have anticonvulsant properties and can terminate status epilepticus.24 Among the volatile anesthetics, methoxyflurane and halothane produce the least CNS irritability; enflurane produces the most irritability, and isoflurane and desflurane produce intermediate levels of irritability.25,26 Changes in the basicity of these compounds, which depends on the degree of fluorination of the carbon atoms adjacent to the ether oxygen, may parallel effects on cortical excitability. Isoflurane, the least fluorinated and most basic of these ethers, produces the least amount of cortical reactivity.25

Adapted from: Najjar S, Devinsky O, Rosenberg AD, et al. Procedures in epilepsy patients. In: Ettinger AB and Devinsky O, eds. Managing epilepsy and co-existing disorders. Boston: Butterworth-Heinemann; 2002;499–513. With permission from Elsevier (

Authored By: 
Orrin Devinsky MD
Souhel Najjar MD
Andrew D Rosenberg MD
Reviewed By: 
Steven C. Schachter MD
Wednesday, March 31, 2004