Dreaming during anesthesia and anesthetic depth in elective surgery patients: a prospective cohort study.
BACKGROUND
Dreaming reported after anesthesia remains a poorly understood phenomenon. Dreaming may be related to light anesthesia and represent near-miss awareness. However, few studies have assessed the relation between dreaming and depth of anesthesia, and their results were inconclusive. Therefore, the authors tested the hypothesis that dreaming during anesthesia is associated with light anesthesia, as evidenced by higher Bispectral Index values during maintenance of anesthesia.


METHODS
With approval, 300 consenting healthy patients, aged 18-50 yr, presenting for elective surgery requiring relaxant general anesthesia with a broad range of agents were studied. Patients were interviewed on emergence and 2-4 h postoperatively. The Bispectral Index was recorded from induction until the first interview. Dream content and form were also assessed.


RESULTS
Dreaming was reported by 22% of patients on emergence. There was no difference between dreamers and nondreamers in median Bispectral Index values during maintenance (37 [23-55] vs. 38 [20-59]; P=0.68) or the time at Bispectral Index values greater than 60 (0 [0-7] vs. 0 [0-31] min; P=0.38). Dreamers tended to be younger and male, to have high home dream recall, to receive propofol maintenance or regional anesthesia, and to open their eyes sooner after surgery. Most dreams were similar to dreams of sleep and were pleasant, and the content was unrelated to surgery.


CONCLUSIONS
Dreaming during anesthesia is unrelated to the depth of anesthesia in almost all cases. Similarities with dreams of sleep suggest that anesthetic dreaming occurs during recovery, when patients are sedated or in a physiologic sleep state.
Leslie
Kate
K
Department of Anaesthesia and Pain Management, Royal Melbourne Hospital, and Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia. kate.leslie@mh.org.au
Skrzypek
Hannah
H
Paech
Michael J
MJ
Kurowski
Irina
I
Whybrow
Tracey
T
D000293:Adolescent; D000328:Adult; D000758:Anesthesia / Q000009:adverse effects*; D015331:Cohort Studies; D004325:Dreams; D017558:Elective Surgical Procedures; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011446:Prospective Studies