Ketamine Infusion for Neuropathic Pain in Brachial Plexus Injuries

Inclusion Criteria:

* Patients with neuropathic pain associated with avulsion injuries following traumatic brachial plexus injuries scheduled for brachial plexus exploration and reconstruction by three senior surgeons at Mayo Clinic (AYS, ATB, RJS):
* Neuropathic pain defined as pain directly related to injury to the somatosensory system, and score \>4/10 on the Douleur Neuropathique en 4 Questions (DN4) neuropathic pain questionnaire. Symptoms of neuropathic pain include allodynia, hyperalgesia, burning, needle-like, throbbing, shooting, or electrical-type sensation.
* Nerve root avulsion on CT myelogram.
* Traumatic brachial plexus injuries defined as blunt or penetrating trauma resulting in injury and dysfunction along the course of the brachial plexus defined as nerve roots C5-T1, trunks, divisions, cords, and terminal branches.

Exclusion Criteria:

* Patients without pain following traumatic brachial plexus injuries.
* Patients with brachial plexus injuries due to non-traumatic causes such as tumors, infection, radiation, or inflammatory disorders such as Parsonage Turner Syndrome.
* Patients who do not require surgery for exploration/reconstruction at the brachial plexus.
* Patients under 18 years of age.
* Contraindication to ketamine use (severe hepatic dysfunction -cirrhosis, high-risk coronary artery disease, poorly controlled psychiatric condition- schizophrenia.