(March 12, 2008 -Insidermedicine) Using a monitoring system based on electrical activity in the brain is no more effective at preventing anesthesia awareness than using a more standard monitoring system involving the assessment of the amount of anesthesia gases patients are exhaling during surgery, according to research published in the New England Journal of Medicine.

Here are some facts about anesthesia awareness:

•    Also called intraoperative awareness, anesthesia awareness refers to incidents in which patients become aware of and remember experiences and events that occurred while they were supposedly under the influence of general anesthesia.

•    Anesthesia awareness is a concern because it can be distressing, even traumatic for patients. Fortunately, it is a rare occurrence.

•    Anesthesia awareness is most likely to occur during high-risk surgeries when the patient’s condition makes deep anesthesia risky. If you are concerned about your risk of experiencing anesthesia awareness, talk to your anesthesia professional.

Researchers from Washington University in St. Louis assessed the presence of anesthesia awareness among nearly 2,000 individuals who underwent general anesthesia using inhaled gases. Depth of anesthesia was monitored by assessing electrical activity in the brain, using a new system called the bispectral index (BIS) or by the standard method, which involves assessing the amount of anesthetic gas the patients exhaled using a system called end-tidal anesthetic gas (ETAG) concentration.

Overall, two patients monitored via BIS and two patients monitored via ETAG experienced definite cases of anesthesia awareness. Among these patients, BIS readings fell outside of their targeted range in one and ETAG concentrations fell out of their targeted range in three. Using BIS did not result in the use of less anesthetic gas during the surgery.

Today’s research demonstrates that using a new technique called BIS to prevent anesthetic awareness may give health care professionals a false sense of security, since it does not appear to be any more effective than standard anesthesia monitoring techniques.

For Insidermedicine in Depth, I'm Dr. Yi Ning Strube.