Research opens up the possibility of using muscle sympathetic nerve activity to quantify pain

Measuring stress activity directed to the blood vessels of muscles could allow researchers to measure pain objectively, according to a new study. Researchers from the Cardiovascular Health and Autonomic Research Lab and Alan Edwards Centre for Research on Pain at McGill University in Canada will present their work this week at the American Physiology Summit, the flagship annual meeting of the American Physiological Society (APS), in Long Beach, California. 

Measuring and treating pain is one of the biggest societal and public health challenges, partly due to its subjective nature. Researchers worldwide struggle to find new ways to accurately measure pain because the "experience is so subjective across individuals. … Verbal pain reports are influenced by contextual factors, so they do not allow for standardization across individuals," said Laila Chaudhry, PhD student and lead author of a new study.

Chaudhry and her colleagues studied a group of young men and women between the ages of 18 and 35. The volunteers participated in a cold pressor test, a common stimulus used to evoke pain. During the test, the participants' hand and wrist were placed in cold water (around 39 degrees Fahrenheit) for up to six minutes. The research team analyzed the volunteers' stress response through measurement of muscle sympathetic nerve activity (MSNA) at multiple points during the cold pressor test. The participants also reported their pain through a numerical pain rating scale commonly used in medical care settings, where 0 indicates no pain and 10 indicates the worst pain possible.

The researchers saw that increased incidence of MSNA bursts-;which typically indicate higher levels of physiological stress-;corresponded with higher subjective pain ratings on the pain scale.

These results open up the possibility of using MSNA to quantify pain, the research team explained.

Biomarkers function as a way to objectively measure pain and even standardize pain responses."

Laila Chaudhry, PhD student and lead author of new study