EVIDENCE FOR UNCONSCIOUS MEMORY PROCESSING DURING ELECTIVE CARDIAC-SURGERY

Background-Many anesthetic drugs have been shown to disrupt conscious recall (explicit memory) in volunteers. However, unconscious processin g (implicit memory) of intraoperative auditory material may occur duri ng general anesthesia and may provide an opportunity for intraoperativ e therapeutic intervention, In this study, we examined patients underg oing elective cardiac surgery for evidence of intraoperative implicit and explicit memory. Methods and Results-Twenty-five subjects provided written informed consent and underwent general anesthesia and cardiop ulmonary bypass for cardiac surgery. During the operation, patients we re randomized to receive 1 of 2 different audiotapes of associated wor d pairs. Postoperatively, a blinded observer conducted a standardized interview to determine the extent of intraoperative implicit and expli cit memory. With the use of free association, significant intraoperati ve implicit memory was found. In contrast, no patient had spontaneous or directed recall of intraoperative events, and we did not find evide nce of intraoperative explicit memory with a recognition task. Conclus ions-Patients undergoing general anesthesia for cardiac surgery were r eliably able to reinforce associations between word pairs solely on th e basis of their intraoperative presentation, This provides further ev idence that patients are capable of processing intraoperative auditory information.