Reduction in the incidence of awareness using BIS monitoring.
BACKGROUND
Explicit recall (ER) is evident in approximately 0.2% of patients given general anaesthesia including muscle relaxants. This prospective study was performed to evaluate if cerebral monitoring using BIS to guide the conduction of anaesthesia could reduce this incidence significantly.


METHODS
A prospective cohort of 4945 consecutive surgical patients requiring muscle relaxants and/or intubation were monitored with BIS and subsequently interviewed for ER on three occasions. BIS values between 40 and 60 were recommended. The results from the BIS-monitored group of patients was compared with a historical group of 7826 similar cases in a previous study when no cerebral monitoring was used.


RESULTS
Two patients in the BIS-monitored group, 0.04%, had ER as compared with 0.18% in the control group (P < 0.038). Both BIS-monitored patients with ER were aware during intubation when they had high BIS values (> 60) for 4 min and more than 10 min, respectively. However, periods with high BIS = 4 min were also evident in other patients with no ER. Episodes with high BIS, 4 min or more, were found in 19% of the monitored patients during induction, and in 8% of cases during maintenance.


CONCLUSIONS
The use of BIS monitoring during general anaesthesia requiring endotracheal intubation and/or muscle relaxants was associated with a significantly reduced incidence of awareness as compared with a historical control population.
Ekman
A
A
Department of Anaesthesia and Intensive Care, Regional hospital, Kalmar, and The Karolinska Institute, Stockholm, Sweden.
Lindholm
M-L
ML
Lennmarken
C
C
Sandin
R
R
D000293:Adolescent; D000328:Adult; D000368:Aged; D000768:Anesthesia, General; D001364:Awareness / Q000187:drug effects*; D004569:Electroencephalography / Q000187:drug effects*; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D019647:Oral Surgical Procedures; D011030:Pneumothorax / Q000601:surgery; D011183:Postoperative Complications / Q000453:epidemiology / Q000523:psychology*; D011184:Postoperative Period; D011446:Prospective Studies; D013548:Sweden; D016896:Treatment Outcome