Professor Paul Myles (Alfred Health and Monash University).
2463 Patients were enrolled between September 2000 and December 2002.
Australia, New Zealand, United Kingdom, Hong Kong and Thailand.
Background
Awareness is an uncommon complication of anaesthesia, affecting 0.1-0.2% of all surgical patients. Bispectral index (BIS) monitoring measures the depth of anaesthesia and facilitates anaesthetic titration. In this trial we determined whether BIS-guided anaesthesia reduced the incidence of awareness during surgery in adults.
Methods
We did a prospective, randomised, double-blind, multicentre trial. Adult patients at high risk of awareness were randomly allocated to BIS-guided anaesthesia or routine care. Patients were assessed by a blinded observer for awareness at 2-6 h, 24-36 h, and 30 days after surgery. An independent committee, blinded to group identity, assessed every report of awareness. The primary outcome measure was confirmed awareness under anaesthesia at any time. incidence of awareness during surgery in adults.
Findings
Of 2463 eligible and consenting patients, 1225 were assigned to the BIS group and 1238 to the routine care group. There were two reports of awareness in the BIS-guided group and 11 reports in the routine care group (p=0.022). BIS-guided anaesthesia reduced the risk of awareness by 82% (95% CI 17-98%). incidence of awareness during surgery in adults.
Interpretation
BIS-guided anaesthesia reduces the risk of awareness in at-risk adult surgical patients undergoing relaxant general anaesthesia. With a cost of routine BIS monitoring at US16 dollars per use in Australia and a number needed to treat of 138, the cost of preventing one case of awareness in high-risk patients is about 2200 dollars.
The B-Aware trial was funded by project grants from the Australian and New Zealand College of Anaesthetists, the Alfred Hospital Research Trust, Royal Hobart Hospital Research Foundation (S Swallow), and the Centre for Encouragement of Philanthropy in Australia.
Myles PS, Leslie K, McNeil J, Forbes A, Chan MT. Bispectral index monitoring to prevent awareness during anaesthesia: the B-Aware randomised controlled trial. Lancet. 2004 May 29;363(9423):1757-63.
Myles PS, Leslie K, Forbes A, McNeil J, Chan MTV. B-Aware: recall of intraoperative events. Lancet 2004; 364:840-842.
Leslie K, Chan MTV, Myles PS, Forbes A, McCulloch TJ. Post-traumatic stress disorder in aware patients from the B-Aware Trial. Anesth Analg 2010; 110:823–828.
Leslie K, Myles PS, Forbes A, Chan MTV. The effect of BIS monitoring on long-term survival in the B-Aware trial. Anesth Analg 2010; 110:816–822.
The full abstract can be viewed on Pubmed.