BRIEF WAKEFUL RESPONSE TO COMMAND INDICATES WAKEFULNESS WITH SUPPRESSION OF MEMORY FORMATION DURING SURGICAL ANESTHESIA

Objective. In a previous study of patients emerging from anesthesia fo llowing surgery, we found that a brief wakeful response to command of an eye opening or single hand squeeze or count was not associated with memory formation, while the response of four hand squeezes or counts was associated with memory. We wanted to determine the anesthetic requ irements for obtaining this brief wakeful response endpoint during sur gery and to determine ii memory occurred at this endpoint during surgi cal anesthesia. Methods. Six different combinations of isoflurane, 70% N2O, and fentanyl were administered to 326 patients undergoing pelvic laparoscopy. After insertion of the trocar, anesthesia was reduced wh ile patients were given verbal commands, and they were observed for mo vement responses to surgery and to command. Patients were classified a s either not arousing, arousing with a movement response to surgery, o r arousing with a wakeful response to command. For the patients who ar oused, we calculated the percentage of arousal responses that were wak eful responses to command. The effect of fentanyl dosage upon the perc entage of arousal responses that were wakeful responses to command was determined by using a Mann-Whitney test to compare a group of patient s receiving fentanyl 2 mu g/kg or less, with a group receiving fentany l 4 mu g/kg. In a subset of 39 patients, the potential for memory form ation was evaluated by presenting a target sound to 29 patients during a period of either no arousal, movement response to surgery, or wakef ul response to command; for a control group of 10 patients, no target sound was presented. All 39 patients were tested for memory of the tar get sound; the results from each group receiving a target sound were c ompared with the results of the control group, using a Mann-Whitney te st. Main Results. A total of 68 patients aroused with either a movemen t response or a wakeful response to command. Wakeful responses occurre d with only 1 of 39 patients (3%) receiving fentanyl 2 mu g/kg or less ; but, wakeful responses occurred with 17 of 29 patients (59%) receivi ng fentanyl 4 mu g/kg. The difference between the groups was significa nt at p 0.01. None of the 68 patients had recall of intraoperative eve nts or unpleasant dreams. None of these patients who were in the multi ple-choice memory subset recalled the target sound. There were no stat istically significant differences on the multiple-choice memory test b etween the groups presented with the target sound and the control grou p. Patient anecdotes suggested that some patients may have had memory of the target sound; but, memory was no more likely in patients with a brief wakeful response to command than in those who responded with a movement to surgical stimulation or those who did not have an arousal response. Conclusions. A brief wakeful response to a command of openin g the eyes or squeezing the hand was not associated with increased mem ory formation during surgery. A brief wakeful response to command was found during surgery when patients received fentanyl 4 mu g/kg; but it was rarely found at fentanyl dosages of 2 mu g/kg or less.