Slightly more than 4 percent of surgical patients are conscious of the external world while under general anesthesia prior to surgery, according to a study published in Anesthesiology, the peer-reviewed journal of the American Society of Anesthesiologists. This percentage is lower than previous estimates of consciousness during surgery.
The researchers used the "isolated forearm technique" to gauge awareness. In this technique, researchers give patients a verbal command to move the hand of a tourniquet-isolated arm. They examined 260 surgical patients.
The researchers found that 4.6 percent of patients were conscious while under general anesthesia, significantly lower than the approximately 37 percent who were identified in previous studies. Additionally, they found that responders were younger than non-responders and they were more lightly anesthetized. They found no known long-term problems associated with the brief period of awareness.
"Although we view such consciousness during surgery as an important issue, we urge caution in the interpretation of these results," said Robert Sanders, MD, of Madison-based University of Wisconsin School of Medicine and Public Health and lead researcher. "We looked at a very brief 'snapshot' of the time patients spend under anesthesia. In addition, these patients likely had very different experiences from those who report being awake but unable to move or speak during surgery."