Anesthesia Can Cause Post-Op Pain

General anesthetics are used to put a patient to sleep during surgery, but new research has found that their use can increase the discomfort that patients feel when they wake up. The hope is that this scientific study, a first to explain anecdotal observations, could lead to increased use of general anesthetics that don't have this type of side effect or the development of a new kind of anesthetic.

The researchers, at a study conducted at Georgetown University Medical Center, found that "noxious" anesthesia drugs, which are most general anesthetics used today, activate and then sensitize specific receptors and neurons in the peripheral nervous system, which could cause pain. These specific sensory nerves are in the inflammatory and pain pathway and aren't affected by general anesthesia drugs that target the central system, like the spinal cord and brain.

Gerard Ahern, the lead investigator and assistant professor in the department of pharmacology, said, "The choice of anesthetic appears to be an important determinant of post-operative pain." He then explained that it was already known that general anesthetics can cause irritation at the site of injection or the airways when inhaled and they can activate pain-sensing nerve cells in our peripheral nervous system.

However, the specific mechanism by which the anesthetics affect sensory neurons was not known, nor the fact that the anesthetics can continue to cause inflammation and pain even as they are used during the surgery.

Ahern and his colleagues found that the noxious affect of the anesthetic drugs are cause by their effect on the never cell receptor named TRPA1. The researchers also found that the nerve-medicated inflammation was greater when pungent (chemical irritants) versus non-pungent inhaled general anesthetic drugs were used on the patients. Both of the findings suggest that the sensory nerve stimulation throughout the body just before and after surgery contributes to the pain that is felt by patients when they wake up after the surgery is finished.

Ahern also stated, "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."

If you wish to further research this study, the results were published in the June 23 issue of the journal Proceedings of the National Academy of Sciences.