Two studies from the February issue of Anesthesiology address the relief of pain. As pain physicians, anesthesiologists are committed to conducting research to better understand and treat patients suffering from acute and chronic pain. The first study examined the link between the type of pain relief provided after breast cancer surgery and the development of chronic pain, while the second study analyzed the connection between the topical drug capsaicin and labor pain.
Breast Cancer Surgery and Chronic Pain
Researchers at the Institut Curie-Hôpital René Huguenin, Saint-Cloud, France, studied the effectiveness of local anesthetic wound infiltration after breast surgery on chronic pain. “We wanted to determine whether the technique of strong pain relief for a short period of time after surgery reduces the development of chronic postsurgical pain,” explained study authors Aline Albi-Feldzer, M.D. and Christian Jayr, M.D., Ph.D.
More than 230 patients scheduled for breast surgery were randomized to receive local anesthetic wound infiltration or placebo wound infiltration. Acute pain, analgesic consumption, nausea and vomiting were examined every 30 minutes for two hours in the postanesthesia care unit and every six hours for 48 hours. Chronic pain was evaluated at three and six months, and one year after surgery.
Findings revealed local anesthetic wound infiltration after breast surgery significantly reduced the incidence of acute pain in patients (no pain at all) by one half in the first 48 hours after surgery, but did not decrease the incidence of chronic pain at three months (33 percent of patients having had local anesthetic wound infiltration and 27 percent of patients having had placebo wound infiltration). The results question the link that some studies have suggested between the severity of acute pain after surgery and the risk of developing chronic postsurgical pain.
Capsaicin and Labor Pain
The role of topical application of capsaicin to the uterine cervix in the reduction of labor pain and the expedition of delivery in mice was analyzed by researchers at the American University of Beirut, Lebanon and Columbia University, NYC. The study analyzed the incidence of four proposed pain behaviors in mice, including no analgesia in labor and the postpartum period, increasing doses of the analgesic morphine, labor pain behaviors and labor progress. The impact of capsaicin on labor pain behaviors and labor progress also was examined.
Findings showed that, in the absence of analgesia, there was a statistically significant increase in all four proposed pain behaviors during labor compared to after delivery, which is consistent with labor being painful in mice. In addition, capsaicin applied days before delivery reduced these labor pain behaviors.
“Capsaicin may emerge as a new, minimally invasive, natural adjunct to the medical induction of labor, one of the most commonly performed obstetrical procedures worldwide,” said study author Fadi G. Mirza, M.D. “In addition, there is a potential global role of capsaicin, particularly in regions with limited access to analgesia and labor-induction agents.”