Pulsed Electromagnetic Fields for Postoperative Analgesia: A Randomized, Triple-Masked, Sham-Controlled Pilot Study

Pulsed electromagnetic field therapy is a possible method of pain control involving the application of electromagnetic energy (also termed nonthermal, pulsed, shortwave radiofrequency therapy). Food and Drug Administration-cleared devices have been in clinical use for over 70 years. For decades, available devices consisted of a large signal generator and bulky coil applicator that were not portable and produced significant electromagnetic interference, making them impractical for common use. However, small, lightweight, relatively inexpensive, noninvasive, Food and Drug Administration-cleared devices that function for 30 days are now available to treat acute and chronic pain, decrease inflammation and edema, and hasten wound healing and bone regeneration. Therefore, it has the potential to concurrently improve analgesia and decrease or even negate opioid requirements, only without the limitations of opioids and peripheral nerve blocks. The purpose of this pilot study is to explore the possibility of treating acute postoperative pain with nonthermal, pulsed shortwave (radiofrequency) therapy, optimize the study protocol, and estimate the treatment effect in preparation for developing subsequent definitive clinical trials.

The proposed study will be a randomized, participant- and observer-masked, sham-controlled, parallel-arm, human participants pilot study with two primary aims:

Specific Aim 1: To determine the feasibility and optimize the protocol for subsequent clinical trials that will compare the addition of nonthermal, pulsed shortwave therapy to usual and customary analgesia following moderate-to-severely painful surgical procedures.

Specific Aim 2: To estimate the treatment effect of adding nonthermal, pulsed shortwave therapy to usual and customary analgesia on pain and opioid consumption following moderate-to-severely painful surgical procedures. This will provide an idea of the optimal surgical procedures amenable to this analgesic technique and allow determination of the required sample sizes of subsequent definitive clinical trials.

Hypothesis 1: Nonthermal, pulsed shortwave therapy decreases pain in the 7 days following moderate-to-severely painful surgical procedures.

Hypothesis 2: Nonthermal, pulsed shortwave therapy decreases opioid use in the 7 days following moderate-to-severely painful surgical procedures.

This will be a single-center (University of California San Diego), randomized, participant- and observer-masked, sham-controlled, parallel-arm human subjects pilot study.

Enrollment. Participants will be consenting adults undergoing various surgical procedures usually resulting in moderate-to-severe postoperative pain. Study inclusion will be proposed to eligible presurgical patients. If an individual desires study participation, written, informed consent will be obtained using a current University of California San Diego Institutional Review Board-approved informed consent form. The study population of interest includes adult women and men of all races, ethnicity, sexual identity, and socioeconomic status.

Procedures. Following written, informed consent, we will record baseline anthropometric information (age, sex, height, weight, amputation details and current pain levels). Participants will receive any standard peripheral nerve block(s) administered using bupivacaine or ropivacaine 0.5% with epinephrine (standard at University of California San Diego) prior to undergoing their surgical procedure per standard of care.

Treatment Group Assignment. Each participant will be randomized to one of two treatment groups: Active or Sham treatment. There are sham devices produced that are identical to active devices, only they do not deliver pulsed electromagnetic energy. Randomization will be stratified by surgical procedure in block sizes of 2. The computer-generated randomization lists will be created by the University of California San Diego Investigational Drug Service in a 1:1 treatment group ratio using opaque envelopes. The active and sham devices are indistinguishable in appearance, and therefore investigators, participants, and all clinical staff other than the individual who opens the randomization envelope and chooses a sham or active device will be masked to treatment group assignment for the duration of the data collection period. An Investigational Drug Service pharmacist will open the envelope and provide the investigators with the appropriate device, keeping all investigators masked to treatment group assignment. Upon completion of data collection for a specific subgroup (e.g., amputees, total knee arthroplasty), the pharmacist will provide the investigators with a masked list of the treatment groups (e.g., "Treatment A" and "Treatment B"), and the active/sham lists only following analysis for that subgroup, resulting in a triple-masked study (investigators, participants, statistician).

Study intervention. The pulsed shortwave device (2 devices, if there are multiple incisions or the incision is larger than the device diameter; 3 devices for total knee and hip arthroplasty or spinal surgery) will be affixed over the primary wound area(s) using tape and activated prior to recovery room discharge (Experimental). The optimal location to treat phantom pain is currently unknown and will partially informed by the results of this pilot study, and patients will be encouraged to move the devices to a new anatomic location until relief is optimized.

Supplemental analgesics. In addition to the pulsed shortwave device(s), participants will receive standard-of-care supplemental analgesics which can include acetaminophen, ibuprofen, ketorolac, opioids, gabapentin (this is provider- and patient-dependent). Therefore, all patients of this study-regardless of the treatment arm they are randomized to-will continue to receive current usual and customary analgesia: all will receive the same combination of supplemental analgesics they would regardless of study participation. Participants (and their caretakers) will be provided with verbal and written instructions, and the telephone and pager numbers of an investigator available during business hours throughout the treatment period. Participants can shower with the device in place, but not submerge it during swimming or a bath, as advised by the manufacturer.

Participants will be discharged with their pulsed shortwave device(s) in situ and a prescription for immediate-release oral opioid, preferably oxycodone 5 mg tablets, taken for breakthrough pain (surgeons occasionally prefer a different type of opioids such as hydrocodone, which is why we analyze the data using oral oxycodone equivalents). The pulsed shortwave devices will be removed by participants at home following Day 30 when the battery is exhausted (participants may remove them as early as Day 7, if they desire). Removing the devices encompasses tape removal and discarding in the trash (these are disposable, single-use devices).

Of note, if a device is reported lost or nonfunctional during the study, it will be replaced by the investigators by mail if more than 7 days of treatment remain.

Study outcomes: This is an exploratory pilot study to assist in planning subsequent definitive trials and we therefore have no data analysis plan. We will enroll convenience samples for each of the surgical procedures of up to 30 participants for each procedure, and anticipate analyzing each surgical procedure separately from the others. The two outcomes of primary interest will be (1) the "average" and "worst" pain measured with the Numeric Rating Scale (included in the Brief Pain Inventory pain domain), and (2) opioid consumption within the first 7 postoperative days.

Eligibility Criteria:
Inclusion Criteria:

Adult patients of at least 18 years of age undergoing one of these primary surgical procedures:

1. non-mastectomy breast surgery with a single-injection paravertebral nerve block
2. laparoscopic cholecystectomy
3. laparoscopic sleeve gastrectomy
4. percutaneous nephrolithotomy
5. ventral hernia repair
6. inguinal hernia repair
7. knee or hip arthroplasty
8. foot/ankle surgery with at least moderate pain anticipated
9. shoulder acromioclavicular joint repair, labral repair, subacromial decompression, or Bankart repair (without rotator cuff repair)
10. hand/forearm/elbow surgery with at least moderate pain anticipated
11. spinal surgery with at least moderate pain anticipated

Exclusion Criteria:

* concurrent use of an implanted pulse generator (e.g., cardiac pacemaker)
* pregnancy
* incarceration
* chronic opioid/tramadol use (daily use within the 2 weeks prior to surgery and duration of use \> 4 weeks)
* neuro-muscular deficit of the surgical area/limb
* a planned postoperative perineural local anesthetic infusion