Really Under During Surgery? Monitor Can Tell
Fri 28 May, 2004 19:27
NEW YORK (Reuters Health) - Horror stories abound of surgery
patients being aware they're being operated on, but unable
to move or say anything. A new type of monitoring should
help prevent that happening.
For every 1000 patients operated on, it's thought that up to
2 become aware during surgery. This can be reduced, an
Australian study suggests, by monitoring brain patterns
during the operation to guide the administration of general
anesthesia.
Monitoring the "bispectral index" (BIS) of brain EEG
patterns indicates the depth of anesthesia and helps the
anesthesiologist make adjustments, according to Dr. Paul S.
Myles from the Department of Anesthesia and Pain Management
at the Alfred Hospital in Melbourne, and colleagues.
However, they note in this week's issue of The Lancet
medical journal, the value of BIS "as a monitor for
awareness has not previously been assessed in a
randomized trial."
To investigate, the team randomly assigned 2463 surgery
patients to BIS-guided anesthesia or standard care. The
patients were questioned about their awareness of the
procedure a few hours, one day, and one month after surgery
by a researcher who did not know which group they were in.
There were two reports of awareness in the BIS group
compared with 11 in the standard care group, meaning
that BIS-guided anesthesia reduced the risk of awareness
by 82 percent.
"BIS monitoring had little effect on the time needed to
recover from general anesthesia, as measured by eye opening,
and no measurable effect on the risks of postoperative
complications," the team notes.
They conclude, based on their results, that "greater use of
BIS monitoring is warranted."
This study is a "great advance," two clinicians from Sweden
write in an editorial.
"In addition to immediate suffering due to pain and anxiety,
other psychological symptoms, or even post-traumatic stress
disorder, might follow after awareness," Drs. Claes
Lennmarken from University Hospital in Linkoping and Rolf
Sandin from the Karolinska Institute in Stockholm comment.
"Clearly the data show that cerebral monitoring has the
potential to further reduce the rate of awareness compared
with traditional measures," they write.
SOURCE: Lancet, May 29, 2004.
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