Anesthesia awareness

Anesthesia awareness, or "intra-operative awareness" occurs during general anesthesia, when a patient receives muscle relaxants but not enough general anesthetic or analgesic to prevent consciousness or, more importantly, 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 are attributed to human error. The others are thought to be due to either a predisposed tolerance or a tolerance induced by the interaction of other drugs. 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 ranges from 0.1% to 0.2 %, or up to 4000 cases per year. The effects usually extend further than the event itself. Many victims experience post-traumatic 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 which is called the electroencephalogram (EEG). At least one study has shown that the use of BIS by anesthesiologists reduces the incidence of awareness.

Reference

Lancet 2004;363:1747,1757-1763.

Prominent victims

• Carol Weihrer, an activist