How you can identify and prevent awareness

Awareness is caused when general anesthesia isn’t sufficient to maintain unconsciousness and to prevent recall during surgery. Common causes include large anesthetic requirements, equipment misuse or failure, and smaller doses of anesthetic drugs, according to a recently published study.1

According to the Joint Commission on Accreditation of Healthcare Organizations, which has issued a sentinel event alert on awareness, contributing factors include the increasing popularity of intravenous (IV) anesthesia delivery, as opposed to inhalation, and the premature lightening of anesthesia at the end of a case to facilitate OR turnover.2

However, not everyone agrees.

"There are no data that I know of that support this statement," says Donald M. Mathews, MD, associate chairman for academic affairs in the department of anesthesiology at St. Vincent’s Hospital Manhattan and assistant professor of anesthesiology at New York Medical College in Valhalla.

The practice of decreasing anesthetics at the end of the case to allow rapid emergence is long-standing and, to Mathews’ knowledge, not controversial in any way, he says. "Most cases of the awareness occur during the induction and intubation or during the body of the procedure, not at the end," Mathews says.

The authors of the recently published study found increased awareness with sicker patients (American Society of Anesthesiologists physical status III-V) undergoing major surgery. The authors say this correlation may reflect the use of smaller anesthetic doses and light anesthetic techniques in sicker patients. Age and sex did not influence the incidence of awareness.1

Other studies are just beginning to be published that show gender differences in responding to a given amount of anesthetic, says Sandra Ouellette, CRNA, MED, FAAN, director of the Nurse Anesthesia Program at Wake Forest University Baptist Medical Center/The University of North Carolina — Greensboro in Winston-Salem and past president American Association of Nurse Anesthetists. In addition, obesity has been defined as a group at risk for awareness, she says.

To prevent awareness, anesthetists can take several steps, Mathews suggests.

Amnestics such as midazolam should be used in cases at high risk for awareness and those where continuous muscle relaxation is planned, he says.

"They should regularly check their vaporizers to ensure that they are full," Mathews says. "They should use anesthetic gas concentration monitoring and have alarms enabled so that if a gas concentration is falling unexpectedly, an alarm sounds."

During a difficult intubation, they need to remember to give repeated doses of hypnotic agents, he says. "They should never treat movement on the OR table with only muscle relaxants," Mathews says.


1. Sebel PS, Bowdle TA, Ghoneim MM. The incidence of awareness during anesthesia: A multicenter United States study. Anesth Analg 2004; 99:833-839.

2. Joint Commission on Accreditation of Healthcare Organizations. Preventing, and managing the impact of, anesthesia awareness. Sentinel Event Alert Oct. 6, 2004; 32:2-3.