PHANTOM LIMB PAIN
What is Phantom Limb Pain?
Phantom limb pain is pain that feels as if it is emanating from a limb that has been amputated. Once assumed to be a psychological problem, the pain is now recognized by physicians as originating in the spinal cord and brain. It often begins a few days after amputation and may be constant or intermittent. It may be brought on by emotional stress or by pressure on the remaining portion of the limb. Researchers now agree that NDMA receptors in the brain are involved.
Phantom Limb Pain Symptoms
Phantom limb pain may feel like shooting, squeezing, throbbing, stabbing or burning and may affect the part of the phantom limb farthest from the amputation site, e.g., the hand of an amputated arm.
Other characteristics of phantom limb pain include:
- Onset within the first few days of amputation;
- Comes and goes or is continuous; and
- Sometimes feels as if the phantom part is forced into an uncomfortable position.
Ketamine and Phantom Limb Pain
Ketamine blocks the NMDA (N-methyl-d-aspartate) glutamate receptor in the brain, and this receptor is involved in the development of phantom limb pain. Therefore, it should come as no surprise that using ketamine to inhibit the pain is being explored as a treatment option.
An ongoing study at Thomas Jefferson University in Philadelphia showed promising initial results in 2016. It looked at 25 patients who had limbs amputated and were treated with ketamine for phantom limb pain within 30 days of surgery.
Of the patients treated, 41 per cent found their pain had lessened. Any hallucinogenic complications the patients experienced were resolved within 24 hours.
Compared to opioid drugs, ketamine has a decreased risk of respiratory depression, and patients exhibited no cardiovascular or neurologic adverse effects from ketamine.
Ketamine for phantom limb pain is administered using an IV drip and patients receive only a small percentage of the dose used in anesthesia. In the U.S., doctors are free to prescribe it off label.