Electroencephalography (EEG)

Patterns

1. Electrocerebral silence
2. Alpha rhythm
3. Burst suppression. Burst suppression occurs during states of deep general anesthesia or coma. Burst suppression is an on/off pattern of EEG activity characterized by periods of high cortical electrical activity followed by periods of low electrical activity. The periods of hyperexcitability are variable but can last 0.5–10 seconds in duration. The periods of low electrical activity or suppression may be due to transient increases in GABAergic inhibition of cortical activity, whereas cortical hyperexcitability may arise from ongoing glutamatergic transmission. Burst suppression results in a significant decrease in cerebral metabolic oxygen rate (approximately 50%). In most cases, the presence of burst suppression is not desirable, as it indicates that the patient is too deeply anesthetized. However, a decrease in oxygen metabolism can have a neuroprotective effect on brain function. As a result, burst pharmacologic burst suppression is medically indicated for traumatic brain injury and for intraoperative neuroprotection during cerebrovascular procedures, such as a carotid endarterectomy or aneurysm clipping. Burst suppression can be induced pharmacologically by administration of barbiturates, propofol, or halogenated anesthetics. A burst to suppression ratio of 1:10 is used as an indication, which means that there is 1 second of burst activity for every 9 seconds of suppression over a 10-second period of EEG recording.
4. Ischemia
5. Hyper-hypothermia
6. Changes in ventilation
7. Artifact

Processing Methods

1. Fourier series analysis
2. Bispectral array
3. Mapping techniques

Intraoperative Monitoring

1. Carotid Endarterectomy
2. Seizure Surgery
3. Cardiac Surgery
4. Deliberate Hypotension
5. Deliberate Hypothermia
6. Barbiturate Coma
7. Intracranial Vascular Procedures