Evaluation of word associations as a reliable postoperative indicator of implicit memory formation during the intraoperative period

Patients expect to receive an anesthetic that prevents the formation of memories during the intraoperative period. Unfortunately, explicit memory formation occurs 40,000 times per year in the United States, while the incidence of implicit memory is thought to be greater. The purpose of the study was to evaluate the effectiveness of word associations as a reliable postoperative indicator of implicit memory formation during the intraoperative period. Forty-eight participants scheduled to undergo general anesthesia for an elective procedure were selected. During the administration of 0.77 +/- .18 microgram/kg per minute of remifentanyl and 0.31 +/- .04 end-tidal volume percent of sevoflurane in air/oxygen, word associations in the form of "Trivial Pursuit" (Hasbro, Inc, Pawtucket, RI) game statements were presented via headphones. Within 24 hours of surgery, each participant was given a postoperative word association test that included the experimental and control word associations. No reports of explicit memory were noted. The experimental word associations were correctly answered 19.3% of the time, while the control word associations were correctly answered 12.8% of the time (P = .014). The findings illustrated that the word association test in the form of Trivial Pursuit game statements/answers may serve as a reliable postoperative indicator of implicit memory formation during the intraoperative period.