Red Heads and Anesthesia

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Study: Redheads Resist Anesthesia

By LAURAN NEERGAARD

..c The Associated Press

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. 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, 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 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. Kurz of Washington University in St. Louis, who praised

the new research.

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.

Cottrell, president of the anesthesiology society. ``It's a very

exciting area.''

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

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.

10/14/02 16:30 EDT

Copyright 2002 The Associated Press. The information contained in the AP

news report may not be published, broadcast, rewritten or otherwise

distributed without the prior written authority of The Associated Press.

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