Anesthesia awareness

Unintended intraoperative awareness wit explicit recall of sensory perceptions during general anesthesia.

Incidence may approach 1% in patients at high risk.

Can lead to anxiety and post-traumatic stress disorder.

Suggested between 20,000 and 40,000 cases may occur annually in the U.S.

Unintended intraoperative awareness can lead to posttraumatic stress disorder in as many as 70% of individuals that experience it (LeslieK et al).

In some cases it may be as a result of inadequate anesthetic dosing and therefore preventable.

Inhaled anesthetic agent is incorporated in the majority of general anesthetics, and concentrations of exhaled anesthetic are routinely measured.

The minimum alveolar concentration (MAC) is the concentration of anesthesia required to prevent 50% of subjects from moving in response to a noxious surgical stimulus, and when the end tidal anesthetic agent concentration is approximately 0.33 MAC, 50% of subjects do not respond to oral commands appropriately, and maintaining this level at greater than 0.7 MAC. during surgery is thought to decrease the incidence of awareness .

Bispectral index monitor processes a single frontal electroencephalographic signal to calculate a patient’s level of consciousness during anesthesia.

Bispectral index values range from zero, indicating the suppression of detectable brain electrical activity, to 100, indicating the awake state.

To prevent anesthesia awareness of the target bispectral index range is between 40 and 60.

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