Vidyya Medical News Service
Volume 6 Issue 152 Published - 14:00 UTC 08:00 EST 31-May-2004 Next Update - 14:00 UTC 08:00 EST 1-Jun-2004
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Anesthesia guidance system can reduce awareness during surgery

Lancet 2004; 363: 1747, 1757-63

An Australian study in this week's issue of The Lancet highlights how the neuromonitoring of brain patterns of patients during surgery could help guide the use of anesthesia and reduce the risk of patients becoming aware during surgery-thought to occur in around 01-02% of patients.

Bispectral index (BIS) monitoring measures the depth of anesthesia by analysis of brain EEG patterns and produces a score between 0 (deep anesthesia) and 100 (awake). Scores of 40-60 are suitable for surgical anesthesia; however, BIS has not previously been assessed in a randomised trial to guide the delivery of anesthesia in order to reduce awareness during surgery.

Paul Myles from Alfred Hospital, Victoria, Australia, and colleagues randomly allocated around 2500 patients known to be at risk of awareness during surgery to receive either BIS-guided anesthesia or standard care. Reported awareness was documented independently a few hours, one day, and one month after surgery.

BIS-guided anesthesia reduced the incidence of awareness during surgery by over 80%; there were only two reported cases of awareness with BIS-guided anesthesia compared with 11 reports among patients given standard care.

Professor Myles comments: "We have shown that use of BIS monitoring can reduce the incidence of awareness under general anesthesia in patients at risk, suggesting that greater use of BIS monitoring is warranted in patients at increased risk of awareness undergoing relaxant general anesthesia".

In an accompanying Commentary (p 1747) Claes Lennmarken from University Hospital, Linkoping, Sweden, concludes: "Myles and colleagues' study is a great leap forward, and hopefully it will also inspire those who have denied the potential of the neuromonitoring technologies to join in the efforts to ensure the sometimes missing component in what was started in 1846-general anesthesia."

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