Persistent Postsurgical Pain

Pain comes in many forms and can be the result of many different things. Postsurgical pain, unlike many maladies involving pain, at least has an identifiable cause. That one silver lining aside, though, the difficulties associated with treatment of postsurgical pain are still daunting, according to Lynn Cintron, MD.

Cintron’s session, “Persistent Postsurgical Pain,” gave an introduction to those challenges, identified eight key ways in which surgery can lead to increased pain, and then presented a series of case studies that had a wide range of outcomes. Cintron called persistent postsurgical pain (PPP) “an unrecognized major health problem,” that affects many—if not most—surgical patients. Cintron displayed a chart showing that low back pain is the most common complaint among pain sufferers (62%), with osteoarthritis (13%) and peripheral neuropathy (11%), the category that includes PPP, next. Surgeries that commonly result in PPP include mastectomy, inguinal hernia, and Caesarean sections.

"Pain is not just a nerve problem," Cintron said. “Pain is a result of biological and psychosocial variables. For example, studies have shown that preoperative anxiety is correlated with more postoperative pain.” Treating persistent postsurgical pain is complicated by “phantom pain,” which is often experienced by amputees, and surgical complications such as infection.

Individual patient experiences vary so widely that it’s difficult to develop best practices for postsurgical treatment. “Risk factors involve the patient as well as the surgery,” Cintron said. “There is more and more data from scientific and genomic studies that patients differ in response to pain and analgesics.” Not all the studies have been replicated, she said, but early evidence shows connections between joint pain and a COMT polymorphism, as well as associations between complex regional pain syndrome (CRPS) patients and the HLA-DQ1 gene.

Though most attendees at the session were not geneticists, the take-home for the pain management specialists, surgeons, and primary care physicians in the audience is to consider high variability in treating postsurgical patients. What works for one patient may not work for another, and the key is to evaluate each patient’s response individually when considering treatment for persistent postsurgical pain. “Our goal as pain management specialists should be a multimodal approach tailored to the needs of the individual,” Cintron said.

Cintron also discussed the many factors that contribute to postsurgical pain, not the least of which is the body’s release of sensitizing mediators that occurs after surgery. Generally called “central sensitization,” or “wind up,” this makes surgical patients much more likely to have lingering neuropathic pain. “Central sensitization reflects the plasticity in the spinal cord,” Cintron said. “Surgery increases synaptic activity in dorsal horn neurons and sets off the release of excitatory transmitters. This kind of neuronal excitability can last days.”

Other players in pain pathways include glia and microglia. In an earlier presentation on pain mechanisms, David Glick, DC, DAAPM, CPE, likened glia to reporters sent by the brain to “gather more information at the injury site.” Cintron explained that, while glia cells are initially helpful, over time and with repeated stimulation, they secrete products that stimulate neurons and add to persistent pain.

Relatively newer pain management therapies, including channel modulators and selective serotonin reuptake inhibitors, do not work by ablating noxious response but by normalizing the hypersensitivity caused by central sensitization. “With many nerve injuries, gray matter is lost which serves as an inhibitor of pain,” Cintron noted.

Studies noted by Cintron have shown that surgery longer than three hours often results in both PPP and poorer outcomes. She also stressed that proper surgical techniques that avoid significant nerve damage, are crucial to minimizing postsurgical pain. “Nerve damage is common in most surgeries, including mastectomy, hernia repair, mandibular osteotomy, and… thoracotomy.” Cintron noted with interest recent evidence that the efficacy of analgesics differs not only among patients but also among surgical procedures, and she suggested several alternatives to conventional surgery that could lower the probability that patients will experience PPP.

The case studies that closed the presentation included a female who had very good results after a mastectomy and was able to return to dancing, and a less fortunate woman who couldn’t wear any shoes at all after a routine bunionectomy. The differences in these results, in which the patient with the much less dramatic procedure ended up with significantly higher PPP, was a poignant reminder of the unpredictability and individual variability associated with pain.