Clinical Trial: Treating Phantom Limb Pain Using Continuous Peripheral Nerve Blocks: A Department of Defense Funded Multicenter Study

Study Status: Recruiting
Recruit Status: Recruiting
Study Type: Interventional

Official Title: Treating Intractable Post-Amputation Phantom Limb Pain With Ambulatory Continuous Peripheral Nerve Blocks

Brief Summary:

When a limb is traumatically severed, pain perceived in the part of the body that no longer exists often develops. This is called "phantom limb" pain, and is different from "stump" pain, which is pain within the part of the limb that remains intact. Unfortunately, phantom pain resolves in only 16% of people, with the rest experiencing this pain for the remainder of the lives. There is currently no reliable treatment for phantom limb pain.

The exact reason that phantom limb pain occurs is unclear, but when a nerve is cut—as happens with a traumatic amputation—changes occur in the brain and spinal cord that actually worsen with increasing phantom pain. These abnormal changes may often be corrected by putting local anesthetic—termed a "peripheral nerve block"—on the injured nerve, keeping any "bad signals" from reaching the brain, with resolution of the phantom limb pain. However, when the nerve block ends after a few hours, the phantom pain returns. But, this demonstrates that the brain abnormalities—and phantom pain—that occur with an amputation may be dependent upon the "bad" signals being sent from the injured nerve(s), suggesting that a very long peripheral nerve block—lasting many days rather than hours—may permanently reverse the abnormal changes in the brain, and provide lasting relief from phantom pain.

Until recently, extending a peripheral nerve block beyond 16 hours was unrealistic. However, a treatment option called a "continuous peripheral nerve block" is now available. This technique involves the placement of a tiny tube—smaller than a piece of spaghetti—through the skin and next to the nerves supplying the amputated limb. The tiny tube may be placed with minimal discomfort in about 15 minutes

Detailed Summary:

Background. The combination of increased munitions force, use of improvised explosive devices, and casualty survival rates has resulted in a dramatic increase in the percentage of injured combat veterans living with a traumatic amputation. Of American Veteran amputees, 35-98% develop chronic, intractable pain perceived as being from the missing limb, a phenomenon termed "phantom limb pain." This pain resolves in only 16% of afflicted individuals, and there is currently no reliable treatment. The etiology of phantom pain remains unclear, but evidence suggests that severing a nerve provokes changes in the spinal cord, thalamus, and cerebral cortex. When neural input from an amputated limb is blocked with local anesthetic (a peripheral nerve block), cortical abnormalities and phantom pain frequently resolve. However, when the single-injection nerve block resolves after a few hours, the phantom pain returns. These findings demonstrate that cortical abnormalities and phantom pain may be maintained from abnormal peripheral input, suggesting that a peripheral nerve block of extended duration—lasting many days rather than hours—may permanently reorganize cortical pain mapping, thus providing lasting relief from phantom pain. A "continuous peripheral nerve block" (CPNB) involves the percutaneous insertion of a catheter directly adjacent to the peripheral nerves supplying an affected limb. Local anesthetic infused via the catheter(s) induces a completely insensate extremity for as long as desired without any systemic side effects. Additionally, CPNB may be provided on an ambulatory basis using a small, portable pump to infuse the local anesthetic.

Objective. To determine if ambulatory CPNB is an effective treatment for intractable phantom limb pain following a traumatic limb amputation. Previously-published small, uncontrolled series describe patient
Sponsor: University of California, San Diego

Current Primary Outcome: Phantom limb pain intensity 4 weeks following initiation of an ambulatory CPNB (as measured by the Numeric Rating Scale within the Brief Pain Inventory). [ Time Frame: 4 weeks post-intervention ]

Current/present, worst, least, and average phantom pain will be assessed using a Numeric Rating Scale (NRS) as part of the Brief Pain Inventory (short form), with the "average" pain score designated as the primary endpoint. In addition, average and worst residual limb pain NRS will be recorded separately from the phantom pain scores. The NRS is a highly-sensitive measure of pain intensity with numbers ranging from 0 to 10, with zero equivalent to no pain and 10 equivalent to the worst imaginable pain.


Original Primary Outcome: Same as current

Current Secondary Outcome:

  • Perception of well-being 4 weeks following an ambulatory CPNB (as measured with the Patient Global Impression of Change Scale). [ Time Frame: 4 weeks post-intervention. ]
    The Patient Global Impression of Change Scale is a 7-point ordinal scale requiring the subject to rate the current severity of their global situation as it relates to phantom limb pain (as defined by each individual) compared to their baseline. This scale has the words "very much worse" to the left by the number one, and "very much improved" to the right, adjacent to the number seven. The words "no change" are in the middle of the scale above the number four. The Patient Global Impression of Change Scale has been validated in over ten prospective trials, including studies specifically involving peripheral neuropathy.
  • Physical and emotional functioning 4 weeks following initiation of an ambulatory CPNB (as measured with the Brief Pain Inventory). [ Time Frame: 4 weeks following initiation of CPNB ]
    The Brief Pain Inventory is an instrument that includes—in addition to pain intensity scales—seven measures evaluating pain's interference with physical and emotional functioning, such as sleep, relations with others, and enjoyment of life. has been used in countless clinical studies of chronic pain,and validated specifically in neuropathic pain states. This instrument is associated with minimal subject burden and is easily interpreted by patients of all ages and education levels.It has high test-retest reliability and correlates well with much longer questionnaires, including the McGill measures and EuroQol.
  • Depression 4 weeks following initiation of an ambulatory CPNB (as measured with the Beck Depression Inventory). [ Time Frame: 4 weeks following initiation of CPNB ]
    The Beck Depression Inventory is a 21-item instrument that measures characteristic symptoms and signs of depression, requires only a 5th grade comprehension level to adequately understand the questions, and demonstrates a high internal consistency (0.73-0.92, mean of 0.86), reliability and validity. Each of the 21 factors is rated on a 0-3 scale, and then summed to produce the total score of 0-63. Mild, moderate, and severe depression is defined with scores of 10-18, 19-29, and 30-63, respectively.


Original Secondary Outcome: Same as current

Information By: University of California, San Diego

Dates:
Date Received: March 30, 2013
Date Started: December 2013
Date Completion: December 2018
Last Updated: October 27, 2016
Last Verified: October 2016