By Pat Anson, PNN Editor

In recent years, many U.S. hospitals have adopted policies that reduce or eliminate the use of opioids after surgery. For some, that means giving their patients Tylenol or Lyrica for postoperative pain. For others, it means trying neuromodulation — a non-pharmacological therapy that new research shows may have some potential.

In a placebo-controlled pilot study led by researchers at University of California San Diego, patients who received percutaneous peripheral nerve stimulation (PNS) had significant reductions in their pain levels after outpatient joint surgery.

Percutaneous PNS is a form of neuromodulation that involves the placement of a tiny wire or “lead” alongside a peripheral nerve. The implanted lead is then connected to a small external pulse generator that sends a mild electric current to the nerve, interrupting pain signals. PNS has been used for years to treat chronic pain, but this was the first clinical trial to assess its use for postoperative acute pain.    

In the pilot study, 65 adult patients scheduled for operations on their shoulders, knees or ankles had leads placed before surgery in the affected joint. After surgery, half of the patients were given neuromodulation, while the other half received a "sham" treatment with a pulse generator that appeared active but did not deliver any electric current.

Patients in both groups received opioids as needed for their postoperative pain, and after one week their pain scores and opioid use were compared.

Researchers reported in the journal Anesthesiology that the results were “much greater than we had anticipated.” Pain scores were over 50 percent lower in patients who received neuromodulation. The mean pain score (on a zero to ten scale) was 1.1 in patients receiving PNS treatment, compared to 3.1 in the sham group.

Nerve stimulation was also associated with an 80 percent reduction in opioid consumption. The median opioid dose (oral morphine equivalent) in the first week after surgery was 5 milligrams in the active treatment group, compared to 48 milligrams in the sham group.

“This multicenter, randomized, double-masked, sham- controlled pilot study provides evidence that ultra-sound-guided percutaneous peripheral nerve stimulation concurrently improves analgesia and decreases opioid requirements to a statistically significant and clinically meaningful degree for at least a week after moderately to severely painful ambulatory orthopedic surgery,” wrote lead author Brian Ilfeld, MD, a professor of anesthesiology at UC San Diego.

Ilfeld and his colleagues say the pain-relieving benefits of neuromodulation continued after the leads were removed 14 days after surgery, but they appeared to wear off after one month. They plan on conducting a larger clinical trial with 250 surgery patients and to follow them for a year to see if there are any long-term benefits from neuromodulation.

Contrary to popular belief, opioid addiction is rare after surgery. A large 2016 study found only 0.4% of older adults were still taking opioids a year after major elective surgery. Another large study in 2018 found only 0.2% of patients who took opioids for post-surgical pain were later diagnosed with opioid dependence, abuse or had a non-fatal overdose.

Nevertheless, the now defunct American Pain Society (APS) released guidelines in 2016 that encourage physicians to use non-opioid medication such as acetaminophen, non-steroidal anti-inflammatory drugs (NSAIDs), gabapentin (Neurotin) and pregabalin (Lyrica) for post-operative pain. The APS also recommended non-pharmacological therapies such as cognitive behavioral therapy and transcutaneous elective nerve stimulation (TENS) as adjunct treatments.

The lead author of the APS guideline was Roger Chou, MD, who also co-authored the 2016 CDC opioid guideline.