Vitamin C is proposed to prevent CRPS. However, there is not enough evidence to recommend this for routine therapy following, for example, a Colles’ fracture. More invasive therapies exist but are outside the scope of emergency medicine. Spinal cord stimulation and intrathecal baclofen pumps have led to a decline in pain. Stellate ganglion block, brachial plexus block, and lumbar sympathetic block have all been used with some success.⁶

The role of lidocaine or ketamine in the management of chronic painful conditions is evolving. Topical lidocaine comes in patches, creams, and ointments. These have been used in CRPS. Options for CRPS include EMLA and 5 percent lidocaine-impregnated patch.¹² Intravenous lidocaine has been evaluated in patients with renal colic and for acute low back pain. It has been proven effective in resolution of pain when used in doses ranging from 1.5 mg/kg to 100 mg IV. Side effects of nausea and dizziness tend to be mild and transient. One study evaluated the use of IV lidocaine infusion in CRPS patients. There was evidence for a decrease in pain response to cold stimuli and, at 3 mcg/mL infusion, a decrease in pain level.¹³ Lidocaine infusions have been advocated for severe and neuropathic pain, as in cancer or diabetic neuropathy. Dosage for testing purposes has been proposed at 1–3 mg/kg (100 mg being a frequently used dose) over 20 to 30 minutes. If the challenge dose is effective, then an infusion at 0.2–2 mg/kg per hour can be given, often with dramatic relief of pain.¹⁴ At this time, the role of intravenous lidocaine in the management of neuropathic pain remains to be defined.

Ketamine has been demonstrated to be efficacious in the management of pain in CRPS.¹⁵ It prevents or attenuates the hyperalgesia and allodynia of CRPS.¹⁶ As noted below, it may prove to be effective in inducing long-term pain relief when administered for four to 14 days.¹⁷

Intravenous ketamine in subdissociative doses may be effective in CRPS. A recent study of low-dose ketamine when used as an infusion initially of approximately 5 mg/hour titrated up to as much as 30 mg/hour for a 70 kg patient over 4.2 days in 60 patients with CRPS demonstrated significant pain relief during a 12-week study period, not simply during its administration.¹⁸ The chance for clinically significant pain reduction for 11 weeks after therapy must be weighed against the cost of hospitalization.

Dr. Glauser is on the faculty of the emergency medicine residency program at MetroHealth Medical Center and professor of emergency medicine at Case Western Reserve University, both in Cleveland. Dr. Money is assistant clinical professor at the Spine Institute at the University of Michigan in Ann Arbor.

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