Redheads Need More Anesthesia
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STUDY: REDHEADS NEED MORE ANESTHESIA
Tuesday, October 15, 2002
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 of Anesthesiologists.
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,
"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 underdose, 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
It's likely the first of many yet-to-be-discovered genetic factors that will
allow anesthesia to be fine-tuned for increased safety, added Dr. James
Cottrell, president of the anesthesiology society. "It's a very exciting
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 explained.
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
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.
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