Featured Research

from universities, journals, and other organizations

Paradox Discovered About General Anesthesia: It Can Increase Post-surgical Pain

Date:
June 24, 2008
Source:
Georgetown University Medical Center
Summary:
The general anesthesia that puts patients into unconscious sleep so they do not feel surgical pain can increase the discomfort they feel once they wake up. The findings, the first to scientifically explain what has been anecdotally observed in the clinic, may lead to wider use of the few anesthetics that don't have this side effect, or to the development of new ones.

The general anesthesia that puts patients into unconscious sleep so they do not feel surgical pain can increase the discomfort they feel once they wake up, say researchers from Georgetown University Medical Center. They say their findings, the first to scientifically explain what has been anecdotally observed in the clinic, may lead to wider use of the few anesthetics that don't have this side effect, or to the development of new ones.

In the June 23rd issue of the Proceedings of the National Academy of Sciences (PNAS), the scientists report that "noxious" anesthesia drugs - which most of these general anesthetics are - activate and then sensitize specific receptors on neurons in the peripheral nervous system. These are the sensory nerves in the inflammation and pain pathway that are not affected by general anesthesia drugs that target the central nervous system -- the brain and the spinal cord.

"The choice of anesthetic appears to be an important determinant of post-operative pain," says the study's lead investigator, Gerard Ahern, Ph.D., an assistant professor in the Department of Pharmacology at Georgetown University Medical Center. "We hope these findings are ultimately helpful in providing more comfort to patients."

It has long been known that general anesthetics cause irritation at the infusion site or in the airways when inhaled, Ahern says. And investigators have also known that while they suppress the central nervous system, they can activate so called "pain-sensing" or nociceptive nerve cells on the peripheral nervous system -- in fact, anesthesiologists often first use a drug to suppress inflammation and pain before delivering the anesthesia to put the patient to sleep.

But what has not been understood is the specific mechanism by which anesthetics affect sensory neurons, or that they can continue to cause pain and inflammation even as they are being used during surgery, he says.

The researchers tested the hypothesis that two specific receptor on the nerves cells (TRPV1 and TRPA1) which are often expressed together and which also react to other irritants, such as garlic and wasabi, were the ones activated by the noxious drugs.

"Plants produce chemicals such as capsaicin, mustard and garlic that were meant to stop animals from eating them. When they are eaten, the two main receptors that react to them are TRPV1 and TRPA1," he says. In fact, TRPA1 is more commonly known as the mustard-oil receptor, and is a principal receptor in the pain pathway, Ahern says.

Experiments showed that general anesthetics appear to regulate TRPA1 in a direct fashion, and are thus responsible for the acute noxious effects of the drugs. Perhaps the strongest evidence is that mice bred without TRPA1 genes demonstrate no pain when the drugs are administered and used, Ahern says. "Most general anesthetics activate the mustard oil receptor, and animals that don't have the receptor don't have irritation," he says.

The research team also found that nerve-mediated inflammation was greater when pungent (chemical irritants) versus non-pungent inhaled general anesthetics were used.

What both findings suggest is that sensory nerve stimulation throughout the body just before and during surgery adds to the pain that is felt after the patient is awake, Ahern says. "This is a provocative finding in terms of the clinical setting, because it was not really recognized that use of these drugs results in release of lots of chemicals that recruit immune cells to the nerves, which causes more pain or inflammation."

Some general anesthetics do not activate the mustard-oil receptor, but they may not be as effective in other ways, Ahern says. "This tells us that there is room for improvement in these drugs."

The study was funded by National Institutes of Health and the National Multiple Sclerosis Society. Co-authors include José Matta Ph.D., Paul Cornett Ph.D., Rosa Miyares B.A., Ken Abe, Ph.D., and Niaz Sahibzada, Ph.D., from Georgetown University.


Story Source:

The above story is based on materials provided by Georgetown University Medical Center. Note: Materials may be edited for content and length.


Cite This Page:

Georgetown University Medical Center. "Paradox Discovered About General Anesthesia: It Can Increase Post-surgical Pain." ScienceDaily. ScienceDaily, 24 June 2008. <www.sciencedaily.com/releases/2008/06/080623175431.htm>.
Georgetown University Medical Center. (2008, June 24). Paradox Discovered About General Anesthesia: It Can Increase Post-surgical Pain. ScienceDaily. Retrieved August 20, 2014 from www.sciencedaily.com/releases/2008/06/080623175431.htm
Georgetown University Medical Center. "Paradox Discovered About General Anesthesia: It Can Increase Post-surgical Pain." ScienceDaily. www.sciencedaily.com/releases/2008/06/080623175431.htm (accessed August 20, 2014).

Share This




More Health & Medicine News

Wednesday, August 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Ebola-Hit Sierra Leone's Freetown a City on Edge

Ebola-Hit Sierra Leone's Freetown a City on Edge

AFP (Aug. 19, 2014) — Residents of Sierra Leone's capital voice their fears as the Ebola virus sweeps through west Africa. Duration: 00:56 Video provided by AFP
Powered by NewsLook.com
101-Year-Old Working Man Has All The Advice You Need

101-Year-Old Working Man Has All The Advice You Need

Newsy (Aug. 19, 2014) — Herman Goldman has worked at the same lighting store for almost 75 years. Find out his secrets to a happy, productive life. Video provided by Newsy
Powered by NewsLook.com
Researcher Testing on-Field Concussion Scanners

Researcher Testing on-Field Concussion Scanners

AP (Aug. 19, 2014) — Four Texas high school football programs are trying out an experimental system designed to diagnose concussions on the field. The technology is in response to growing concern over head trauma in America's most watched sport. (Aug. 19) Video provided by AP
Powered by NewsLook.com
American Ebola Patient Apparently Improving, Outbreak Is Not

American Ebola Patient Apparently Improving, Outbreak Is Not

Newsy (Aug. 19, 2014) — Nancy Writebol, an American missionary who contracted Ebola, is apparently getting better, according to her husband. The outbreak, however, is not. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins