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

• Status: Completed
• Trial end date: 2020-10-01
• Target enrollment: 0
• Participant gender: All

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. Numbing medicine called local anesthetic is then infused through the tube, blocking any signals that the injured nerve sends to the spinal cord and brain. Using a small, portable infusion pump, this prolonged nerve block may be provided in individuals' own homes.

The ultimate objective of the proposed research study is to determine if a 6-day continuous peripheral nerve block provided at home is an effective treatment for persistent phantom limb pain following a traumatic limb amputation. The primary hypothesis (what the researchers predict) is that phantom limb pain intensity will be significantly decreased 4 weeks following treatment with a 6-day continuous peripheral nerve block.

• Phase: Phase 4
• Accepts Healthy Volunteers?: No

Details

• Lead Sponsor: University of California, San Diego
• Collaborator: United States Department of Defense

Criteria

Inclusion Criteria:

• 18 years of age or older

• Upper or lower limb traumatic or surgical amputation at least 12 weeks prior to enrollment at or distal to the mid-humerus or hip (femoral head remaining), respectively; and including at least one metacarpal or metatarsal bone, respectively.

• Experiencing at least moderate phantom limb pain (defined as 2 or higher on the numeric rating scale, NRS 0-10), at least three times each week for the previous 8 weeks.

• Accepting of an ambulatory continuous peripheral nerve block for 6 days.

• Willing to avoid changes to their analgesic regimen from 4 weeks prior to and at least 4 weeks following the initial catheter placement (preferably 4 weeks following the second/crossover catheter insertion as well).

• Having a "caretaker" who will transport the subject home following the catheter insertion(s), and remain with the subject for the first night of the infusions.

Exclusion Criteria:

• Known renal insufficiency

• Allergy to study medications

• Pregnancy

• Incarceration

• Inability to communicate with the investigators

• Morbid obesity (BMI greater than 40)

• Comorbidity that results in moderate-to-severe functional limitation (ASA greater than 2)

• Possessing any contraindication to ambulatory perineural catheter placement or perineural local anesthetic infusion:

• Current infection

• Immune-compromised status of any etiology

• Uncontrolled anxiety/panic disorder

• Inability to contact investigators during the perineural infusion