Genetics Play Significant Role in Post-Surgical Pain

By Pat Anson, Editor

An important new study has confirmed that a patient’s genes really do play a role in determining whether they develop chronic pain after surgery.

Researchers in China collected blood samples from 1,152 surgical patients to look for genetic variations in 54 "pain-related" genes which have been associated with pain sensation. Patients were then contacted a year later to see if they had chronic post-surgical pain.

A surprising number – one out of five patients – still experienced pain at the wound site, and 33 percent of them said their pain was severe.  Patients with pain also reported problems with their overall health, as well as daily activities such as mood, walking, relations with others, sleep, and quality of life.

Aside from genetic factors, the study also found patients younger than 65, males, and those with a prior history of chronic pain were at increased risk. The study is published online in the journal Anesthesiology.

"Our study not only shows there are common genetic variations among people that may help to identify whether they are at high-risk for developing chronic pain after surgery, but it also helps explain why only a fraction of patients ever even experience persistent pain," said lead researcher Matthew T.V. Chan, MD, at the Chinese University of Hong Kong.

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"Until now, the genetic variations associated with chronic post-surgical pain have not been well identified."

One genetic variation in particular - a gene found in the nervous-system called brain-derived neurotrophic factor (BDNF) - was found to be most frequently associated with chronic post-surgical pain. Researchers confirmed the finding in a study on laboratory mice.

The researchers also found that genetic variations account for a higher percentage of chronic post-surgical pain (between 7 percent and 12 percent) than other risk factors such as age, sex, smoking history or anesthesia technique (between 3 percent and 6 percent).

Chronic post-surgical pain is one of the most common and serious complications after surgery. Previous studies have found that chronic pain was common after abdominal hysterectomies (25.1%) and heart or lung surgery (37.6%).

“Considering that more than 230 million surgeries are performed each year worldwide, the data would imply that millions of patients will continue to suffer wound pain, months to years after their surgery,” researchers said.

The study comes at a time when many U.S. states have adopted or are enacting laws that would limit the supply of opioid medication to just a few days for acute short-term pain. Minnesota, for example, is close to adopting strict guidelines that would limit the dose and supply of opioids to three days for acute pain and seven days after a major surgery.

Post-Surgical Pain Guidelines Reduce Use of Opioids

By Pat Anson, Editor

The American Pain Society (APS) has released new guidelines for post-surgical pain management that encourage physicians to limit the use of opioids and offer “multimodal therapies” to patients suffering from postoperative pain.

According to studies, more than half of patients who undergo surgery receive inadequate pain relief, which can heighten the risk of developing chronic pain, mood disorders and disability.

The 32 recommendations were developed by a panel of nearly two dozen experts that reviewed over 6,500 scientific studies. Most of the recommendations were adopted unanimously.

“The intent of the guideline is to provide evidence-based recommendations for better management of postoperative pain, and the target audience is all clinicians who manage pain resulting from surgery,” said lead author Roger Chou, MD, a prominent researcher who also co-authored the proposed opioid prescribing guidelines developed by Centers for Disease Control and Prevention.

Like the CDC guidelines, the APS guidelines encourage the use of non-pharmacological therapies and non-opioid medications, such as acetaminophen, non-steroidal anti-inflammatory drugs (NSAIDs), gabapentin (Neurotin) and pregabalin (Lyrica). Those treatments would be used along with opioids for post-operative pain.

“Because of the availability of effective non-opioid analgesics and non-pharmacologic therapies for postoperative pain management, the panel suggests that clinicians routinely incorporate around the clock non-opioid analgesics and non-pharmacologic therapies into multimodal analgesia regimens,” the guideline states.

“Systemic opioids might not be required in all patients. One study suggests that it should be avoided when not needed, because limited evidence suggests that perioperative opioid therapy might be associated with increased likelihood of long-term opioid use, with its attendant risks.”

Chou says using multiple approaches to pain management provides better pain relief than a single analgesic.

“Randomized trials have shown that multimodal anesthesia involving simultaneous use of combinations of several medications -- acting on different pain receptors or administered through different techniques -- are associated with superior pain relief and decreased opioid consumption compared with use of a single medication administered by one technique,” Chou said.

The APS panel also recommends that non-pharmacological therapies, such as cognitive behavioral therapy and transcutaneous elective nerve stimulation (TENS), can be used as effective adjuncts to pain medication.

Other recommendations in the APS guidelines include:

  • Adults and children can be given acetaminophen and/or NSAIDs for postoperative pain management
  • Oral administration of opioids is preferred over intravenous (IV) administration
  • Spinal analgesia (epidurals) is appropriate for major thoracic and abdominal procedures
  • Use of benzodiazepines, tramadol and ketamine is not recommended for postoperative pain.
  • Clinicians should consider giving preoperative doses of celecoxib (Celebrex) to adult patients
  • Gabapentin (Neurotin) and pregabalin (Lyrica) can be considered for postoperative pain relief.  The drugs are associated with lower opioid requirements after surgery.

The guidelines recommend the physicians consult with a pain management specialist when a patient has a tolerance for opioids, or a history of substance abuse or addiction.

“Adequate pain treatment should not be withheld from patients with active or previous opioid addiction because of fears of worsening addiction or precipitation of relapse. In addition to the ethical requirement to address postoperative pain, poorly treated pain can be a trigger for relapse,” the guidelines say. “An interdisciplinary approach using pharmacologic and nonpharmacologic interventions might be required to achieve successful postoperative outcomes and should be considered as part of the perioperative management plan in these patients.”

The APS post-operative pain guidelines, which are being published in the Journal of Pain, was endorsed by the American Society for Regional Anesthesia. A link to the guidelines can be found here.