Wednesday, October 03, 2007

New anesthesia method blocks pain without numbness or paralysis

New anesthesia method blocks pain without numbness or paralysis

By Colin Nickerson, Globe Staff

The world's hottest work in anesthesiology is being done at Harvard, where researchers are pouring pepper on pain.

Scientists at Harvard Medical School and Massachusetts General Hospital today described a new "targeted" approach to anesthesia that appears to totally block pain neurons, but doesn't cause the numbness or partial paralysis that is the unwelcome side-effect of anesthesia used for surgery performed on conscious patients.

If approved for use in humans, the method could dramatically ease the trial of giving birth -- by sparing women pain while allowing them to physically participate in labor. It could also diminish the trauma of knee surgery, for instance, or the discomfort of getting one's molars drilled. Not only would there be no "ouch," there would be none of the sickening wooziness or loss of motor control that comes from standard forms of "local" anesthesia.

In time, the process might even be employed for major surgery on the heart and other organs, the researchers said. More prosaically, the work might also represent a breakthrough cure for the common itch.

The work on lab rats, described in the scientific journal Nature, breaks from the standard approach to local anesthesia, which usually involves anesthetics delivered by catheter tubes or injections that silence all neurons in a given region of the body, not just those that sense pain. Shutting down just the pain neurons means that patients could still feel a light touch and other non-hurtful sensations.

"This could really change the experience of, for example, knee surgery, tooth extractions, or childbirth," said Dr. Clifford Woolf, senior author of the study and a researcher in anesthesia and pain management at Mass. General. "The possibilities are almost endless."

Woolf collaborated with Bruce Bean, professor of neurobiology at Harvard Medical School, in research that employed surprisingly basic scientific principles as well as some unlikely ingredients -- capsaicin, the stuff that imparts "hot" to chili peppers, as well as an all-but-forgotten variation of a standard anesthesia, long dismissed as clinically useless.

"We plucked a little of this and little of that off the shelves," Bean said. "The project is really a great illustration of how basic biological principles can have very practical applications."

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