Study: Redheads need more anesthesia
WASHINGTON (AP) − The genetic quirk that makes red
hair red may also make carrot-tops harder to knock out
− in the operating room, that is.
A new study suggests
people with naturally red hair need about 20 percent more
anesthesia than patients with other hair colors.
It's a small study that will need confirmation. But it
marks the first time scientists have linked a visible
genetic trait to anesthesia doses, said Dr. Daniel
Sessler of the University of Louisville, whose study will
be presented Tuesday at a meeting of the American Society
Inadequate doses of general
anesthesia can allow people to recall surgery, or even
wake up during it, problems that occur in 1 percent of
cases, Sessler said.
"If redheads require more anesthesia and are not
given more, their chances of having recall during
surgeries increase," he said.
Determining a patient is properly anesthetized is a
partly an art: Physicians must watch for sometimes subtle
signs of an under dose, like slight movements or
sweating, as well as overdose warnings such as low blood
pressure or heart rate. So knowing if a particular group
of people is more likely to need a higher- or
lower-than-standard dose could be very useful.
Anesthesiologists have long grumbled that redheads can
be a little harder to put under, but no one had ever
studied if that was real or folklore, said Dr. Andrea
Kurz of Washington University in St. Louis, who praised
the new research.
But why would hair color possibly matter? The theory hinges on melanin, a
pigment responsible for skin and hair color.
The sun triggers a hormone that in turn triggers the
production of melanin to form a tan. Redheads seldom tan
easily because they have a defective receptor for that
hormone − a quirk with this "melanocortin-1
receptor" that also leaves their hair red. Without
its intended receptor to dock in, the melanin-producing
hormone may cross-react with a related receptor on brain
cells that influences pain sensitivity, Sessler
That's still a theory. Here's what Sessler can say for
certain: He and colleagues gave 10 healthy women with
naturally red hair and 10 with dark hair the common
inhaled anesthetic desflurane. Then they administered
electric shocks − not enough to do damage but enough to
cause pain − and inched the desflurane dose up or down
according to the pain response until each patient was
judged to be at the optimum anesthetic dose. The redheads
required a 20 percent higher dose.
Sessler said his lab first tested a few blondes and found
they reacted the same as brunettes. That was expected
since only redheads have the melanocortin-1 defect.
The study doesn't address if men
would react similarly − there are gender differences
for many drugs − or if redheads would be similarly
affected by non-inhaled types of anesthesia.
Still, the research "gives us a window into what
determines anesthetic requirements," said Sessler,
whose lab is beginning more studies to see if the melanin
theory is right.
CNN News（CNN.com）：15, October,2002
receptor：a nerve ending that reacts to a change, such
as heat or cold, in the body by sending a message to the
central nervous system
（１） A new study について、
（４)The study〜of anesthesiaについて、