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.
