• Onuma Chaiwat, Kamheang Vacharaksa, and Ungkab Prakanrattana.
• Department of Anesthesiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
• J Med Assoc Thai. 2002 Sep 1;85 Suppl 3:S948-55.

ObjectiveTo determine the occurrence and associated factors of awareness in the patients undergoing elective surgery under general anesthesia.MethodsA prospective cohort study of 802 patients, scheduled for elective general and gynecological surgery under endotracheal anesthesia was performed at Siriraj Hospital. Balanced general endotracheal anesthesia was performed as routine practice. Standard monitoring and clinical observation for movement, tear, sweat, and eye-lid opening were obtained. They were interviewed during the first 12 hours after a surgical completion. If the patient was suspected to have awareness, then a second interview was performed on postoperative day 3.ResultsThe ages of the study population were 16-84 years. There were 659 females and 143 males. Awareness was found in 5 patients (3 females, 2 males) as an occurrence of 0.62 per cent. The only positive clinical observation found was hand movement. The cause of awareness should be inadequate anesthesia. Apart from that, data gathered from interviews with the group who had no awareness (797 patients), the last thing they could remember before unconsciousness was auditory perception. Also hearing someone calling was the first thing upon awakening. Most of the patients did not dream during anesthesia. No serious psychological disorder occurred.ConclusionThe occurrence of awareness was 0.62 per cent in the patients undergoing surgery under anesthesia. Inadequate anesthesia was the most likely cause of awareness. No postoperative sequelae of awareness occurred.

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