Anesthesia closer to coma than sleep

The status of brain under general anesthesia is more like a reversible drug-induced coma rather than sleep, a new study suggests.

Despite what patients may hear before surgery, there are significant differences between general anesthesia and sleep, with only a bit of overlap between the deepest states of sleep and the very lightest phases of anesthesia, wrote 3 neuroscientists who reviewed the latest research in general anesthesia, sleep and coma.

Comparing the physical signs and brain patterns of patients under anesthesia and those who were asleep suggests that general anesthesia is a drug-induced reversible coma on a different time scale, according to the issue published in the New England Journal of Medicine.

There is substantial overlap between the electroencephalograms (EEG) of patients in coma and of patients during general anesthesia, authors said.

"The [electroencephalogram] of the states of coma recovery can resemble those of the awake, general anesthesia, or sleep state, depending on how extensive the brain injury is and where the patient is in terms of recovery," noted Emery N. Brown from Harvard Medical School.

The team also noted that anesthetic drugs induce unconsciousness or alter arousal through actions at multiple sites in the cerebral cortex, brainstem and thalamus.

Referring to the similarities between coma and general anesthesia Nicholas D. Schiff from Weill Cornell Medical College believe that monitoring brain function under general anesthesia may lead to the development of new sleep aids and new ways for patients to recover from coma.