In an interview of 2612 patients after general anesthesia, 10 (0.4%) patients with awareness and 9 (0.3%) patients with possible awareness were found. A predisposing factor was small doses of the principal anesthetic. In a psychiatric interview, a large proportion of the patients with awareness were found to have suffered from depression in the past.

Conscious awareness with recall as a complication of general anesthesia has existed for as long as general anesthesia itself. In 1846, William Morton gave the first anesthetic to Gilbert Abbott in a demonstration at the Massachusetts General Hospital in Boston. Gilbert Abbott told later that he was aware during the anesthetic but felt no pain. Only a small number of further reports of awareness during anesthesia were published in the nineteenth and in the early twentieth century (Ghoneim, 2001). In the early days of anesthesia, the practice of using a single general anesthetic agent in relatively high concentrations to produce all components of general anesthesia-unconsciousness, relief from pain, absence of reflexes, and muscle relaxationapparently protected the patients from traumatic awareness. Moreover, neuromuscular blocking agents (NMB) were not available, and patients were, therefore, able to signal awareness by movement. When NMBs were introduced into anesthetic practice to improve operative conditions and to reduce the toxicity of general anesthetic agents, traumatic awareness became possible. The first case report of traumatic conscious awareness with later recall during general anesthesia was described in 1950 (Winterbottom, 1950). Perhaps describing the