Red hair = more pain sensitivity?


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WASHINGTON (Reuters) - Redheads may actually have another trait that makes
them stand out – sensitivity to pain, specialists reported on Tuesday.

People with natural red hair need about 20 percent more anesthesia than
people with other hair colors, they told a meeting of anesthesiologists. The
unexpected finding not only suggests that redheads are more sensitive to
pain, but offers insights into how anesthesia works in people.

“Red hair is the first visible human trait, or phenotype, that is linked to
anesthetic requirement,” Dr. Edwin Liem of the University of Louisville in
Kentucky said in a statement.

“In a nutshell, redheads are likely to experience more pain from a given
stimulus and therefore require more anesthesia to alleviate that pain,” he
added.

Liem, who reported his findings to a meeting in Orlando, Florida of the
American Society of Anesthesiologists, said the finding is important news
for specialists who monitor patients during surgery.

“The art and science of anesthesiology is choosing the right dose,” he said.
“There is very little difference between the effective dose and the toxic
dose of most anesthetics. Patients can awaken during surgery if they are
given insufficient anesthesia or suffer cardiac and pulmonary complications
when they are given too much.”

He said scientists do not fully understand how anesthesia works, but the
findings offers clues, as people with red hair have a certain genetic
variant.

“Since red hair can be traced to particular mutations (variations) in the
melanocortin 1 receptor, we now have the opportunity to evaluate central
nervous system pathways that may influence or mediate anesthetic
requirement,” Liem said.

“Investigating the role of melanocortin system in the central nervous system
is thus likely to help us understand fundamental questions such as which
systems in the brain produce unconsciousness and which modulate pain
perception.”

Liem’s team studied white women aged 19 to 40 who were given the inhaled
anesthetic desflurane. Their physical responses were closely monitored,
especially unconscious reflex arm or leg movement in response to painful
stimulation.

More anesthesia was needed to block movement in redheads than in
participants with dark or blond hair, Liem said.