1. 2010;13;365-368The Use of Sub-Anesthetic Intravenous Ketamine and Adjuvant Dexmedetomidine when Treating Acute Pain from CRPS
   Case Report
   Sharanya Nama, BS, Daniel R. Meenan, MD, DMD, and William T. Fritz, MD.

Complex regional pain syndrome (CRPS) is a pain condition of the extremities that presents with pain and allodynia, decreased range of motion, swelling and skin changes. There are 2 forms of CRPS — Type I which does not have demonstrable nerve lesions and Type 2, which has evidence of obvious nerve damage. Management of refractory CRPS has been challenging. Some studies have revealed that the N-methyl-D-aspartic acid receptor (NMDAR) may be involved in the etiology of the pain in CRPS and perhaps that a NMDA receptor antagonist like Ketamine is a potential treatment for CRPS. However, the side effect profile of ketamine is concerning, and limiting the adverse effects of the drug is beneficial. Dexmedetomidine is an alpha 2 agonist similar to clonidine with analgesic properties that can be used in combination with ketamine to provide additional analgesia in CRPS.

This case describes the treatment of acute pain symptoms from Chronic Regional Pain Syndrome-Type 1 (CRPS-1) with sub-anesthetic intravenous infusion of ketamine with adjunct dexmedetomidine. A 47-year-old female patient presented with severe pain, burning and allodynia from CRPS-1 refractory to conventional therapy. She was then admitted to a monitored bed, received a sub-anesthetic intravenous infusion of ketamine with adjunct dexmedetomidine for 19 hours and subsequently discharged with complete resolution of her pain and associated symptoms. Here, the synergistic effect of the ketamine and dexmedetomidine together is shown to provide excellent symptom relief while decreasing the total ketamine administered. The combination minimized unwanted side effects and eliminated the need for intensive care unit admission secondary to anesthetic doses of ketamine.