Efficacy of IV ketamine to treat pain disrorders in the pain clinic

Ketamine is a potent blocker of NMDA-subtype glutamate receptors, thought to play a role in pain transmission. We chose to study this agent IV in the pain clinic to treat pain flareups.

30 patients (22=f, 8=m) were treated for refractory pain in the clinic. 7 different types of pain syndromes were treated, including face, eye and limb pain. 16 had co-existent migraine problems. An IV was placed and pulse oximetry was used in each patient. 0.4mg ketamine/kg was administered by IV infusion over 90 minutes. If there were no side effects, another 0.4mg/kg was administered over the same time. Patients rated their pain on a 0-10 VAS. 12 patients received a single infusion, while the rest received between 2 and 12 IV infusions.

Beginning pain severity was 6.5/10 and this reduced to 2.43/10 after treatment (p<.001). Average ketamine infusion time was 137.9 min and the average dose of ketamine was 65.2 mg. Side effects were transient “spaciness” in 4 patients and a sense of exhilaration in 4 more. No person fell asleep during treatment.

We conclude that IV ketamine for treating refractory pain is a very effective new form of treatment with implications for pain pathophysiology and double-blins studies are warranted.