Anesthesia awareness

Anesthesia awareness, or "intra-operative awareness" occurs during general anesthesia, when a patient is paralyzed with muscle relaxants but not enough general anesthetic or analgesic to prevent consciousness or, more importantly, the sensation of pain and the recall of events.

The experience is often extremely traumatizing for the patient who is unable to communicate his or her distress due to the muscle relaxants.

Most current cases of anesthesia awareness are attributed to human error. The others are thought to be due to either a predisposed drug tolerance or a tolerance induced by the interaction of other drugs. Inability to reliably measure consciousness with current technology is another important factor. The causal human errors include inadequate drug dose, inadequate monitoring, and failure to refill the anesthetic machine's vaporisers with volatile anesthetic.

The prevalence of anesthesia awareness in the United States is 20,000 to 40,000 cases per year, which represents 0.1 percent and 0.2 percent of all patients undergoing general anesthesia (JCAHO 2004). The effects usually extend further than the event itself. Many victims experience posttraumatic stress disorder (PTSD), leading to long-lasting after-effects such as nightmares, flashbacks, and insomnia. It is also highly comorbid with alcoholism.

As with all forms of medical error, incidents of awareness are under-reported. Inadequate education about the full impact of awareness leads to an inadequate response by anesthesiologists and delayed treatment for victims. In many cases, doctors have ignored the post-operative complaints and have not referred patients for appropriate counselling.

As an additional preventative measure, some hospitals use a new device called a bispectral index monitor (BIS). BIS monitors the electrical pattern of brain activity, otherwise known as an electroencephalogram (EEG). At least one study has shown that the use of BIS by anesthesiologists reduces the incidence of awareness.

See also

• Carol Weihrer, victim and activist
• Iatrogenic
• Awake, a 2006 film about anesthetic awareness

References

• Myles PS, Leslie K, McNeil J, Forbes A, Chan MTV, for the B-Aware trial group. Bispectral index monitoring to prevent awareness during anaesthesia: the B-Aware randomised controlled trial. Lancet 2004;363:1757-1763. Fulltext. PMID 15172773.
• Joint Commission on Accreditation of Healthcare Organizations (JCAHO). Sentinel Event Alert 6 Oct 2004;32. Online version.