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Anesthetic Drugs and the Electroencephalogram

Drug Effect on EEG Frequency Effect in EEG Amplitude Burst Suppression
Isoflurane Yes, >1.5 MAC
Subanesthetic Loss of α, ↑ frontal β  
Anesthetic Frontal 4- to 8-Hz activity  
Increasing dose >1.5 MAC Diffuse θ and δ → burst suppression → silence ↑ → 0  
Enflurane Yes, >1.5 MAC
Subanesthetic Loss of α, ↑ frontal β  
Anesthetic Frontal 7- to 12-Hz activity  
Increasing dose >1.5 MAC Spikes/spike and slow waves →

Burst suppression; hypocapnia →

Seizures
↑↑  
Halothane Not seen in clinically

useful dose range
Low dose ↑ Frontal 10- to 20-Hz activity  
Moderate dose Frontal 10- to 15-Hz activity  
Increasing dose >1.5 MAC Diffuse θ, slowing with increasing dose  
Desflurane Similar to equi-MAC dose of isoflurane Similar to equi-MAC
dose of isoflurane
Yes, >1.2 MAC
Nitrous oxide (alone) Frontal fast oscillatory activity (>30 Hz) ↑, especially with inspired concentration >50% No
Barbiturates Yes, with high doses
Low dose Fast frontal β activity Slight ↑  
Moderate dose Frontal α frequency spindles  
Increasing high dose Diffuse δ → burst suppression → silence ↑↑↑ → 0  
Etomidate Yes, with high doses
Low dose Fast frontal β activity  
Moderate dose Frontal α frequency  
Increasing high dose Diffuse δ → burst suppression → silence ↑↑ → 0  
Propofol Yes, with high doses
Low dose Loss of α, ↑ frontal β  
Moderate dose Frontal δ, waxing-waning α  
Increasing high dose Diffuse δ → burst suppression → silence ↑↑ → 0  
Ketamine No
Low dose Loss of α, ↑ variability ↑ ↓  
Moderate dose Frontal rhythmic θ  
High dose Polymorphic δ, some β ↑↑ (β is low amplitude)  
Benzodiazepines No
Low dose Loss of α, increased frontal β activity  
High dose Frontally dominant δ and θ  
Opiates No
Low dose Loss of β, α slows ↔ ↑  
Moderate dose Diffuse θ, some δ  
High dose δ, often synchronized ↑↑  

α = alpha (8-13 Hz) frequency; β = beta (>13 Hz) frequency; δ = delta (
Note: Arrows indictate direction of change; number of arrows indicates the magnitude of change.

Adapted from Black S, Mahla ME, Cucchiara RF. Neurologic Monitoring. In RD Miller. (ed). Anesthesia. New York: Churchill Livingston, 1994:1323.

Authored by: S Black | ME Mahla | RF Cucchiara
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