This article on awareness with recall during general anesthesia (AWR) by Errando et al (Br J Anaesth 2008;101:178-185) has a number of interesting observations. First, it is from a country (Spain) other than the United States. Second, it is prospective with a calculated power to detect a 95% confidence interval of 0.09 – 0.37%. Third, it covers a fairly long time in two separate data collection periods (April 1995 – April 1997 and then December 1998 – November 2001). Interviews were done in the PACU immediately post op. If there was evidence of awareness then the patients were interviewed again at 7 days and 30 days (in my opinion this is a design flaw compared to the current standard of interview regardless of initial response). Patients going to the ICU were excluded, as were patients less than 15 years old and those having cardiac surgery. Patients aware because erroneous administration of neuromuscular blocker prior to a hypnotic drug were classified as not having AWR. The interviews were formally structured. The interviewers did not know the anesthetic given.
Data from 4001 patients cared for by 42 different anesthesiologists at one institution was reported. The incidence of patients reporting AWR 7 days after elective surgery was 0.6% (22 of 3477 pts). Of interest was a difference in awareness depending on anesthesia type. Patients who received only nitrous oxide oxygen for maintenance had an AWR rate of 5% (4 of 79 pts), with total intravenous anesthesia the reported AWR was 1.1% (14/1239), but when halogenated anesthetic drugs were used the AWR was only 0.59% (9/1514). Patients receiving a benzodiazepine pre medication (dose and type not provided) had significantly less recall than those who received an opioid pre medication. Twenty two patients with AWR provided descriptions of the experience. 11 reported hearing noise; 18 reported hearing conversations. Twelve patients tried to move and 14 tried to communicate but could not. Eleven patients had pain; five reported being cut with a scalpel and five felt suturing. Nine reported feeling the tracheal tube in their mouth. Eleven felt panic at the time they were awake and two had a sensation of eminent death. Few if any of the patients discussed the event with their anesthesiologist though 16 told their surgeon. Six episodes occurred at the beginning of surgery, two during and seven at the end. From an analysis of the anesthesia record, in only 2 patients was awareness suspected by those caring for the patient. Three of the patients had difficult intubation. In fifteen patients there were errors in hypnotic drug dose and in two there were equipment failures. My observations – their numbers of aware patients may have been even higher if they had included the CT patients. These are high numbers compared to many of the recent United States studies; however their data comes from an earlier period (1995 – 2001). In any event awareness under anesthesia is not just a United States phenomenon. Their data on anesthesia type having an effect, a potential role for benzodiazepine pre medication and their descriptions of what it is like to be aware during surgery makes this paper worth reading.
David S. Smith, M.D., Ph.D.