Sympathetic Blocks as a Predictor for Response to Ketamine Infusion in Patients with Complex Regional Pain Syndrome: A Multicenter Study.

Background: Ketamine infusions are frequently employed for refractory complex regional pain syndrome (CRPS), but there are limited data on factors associated with treatment response. Sympathetic blocks are also commonly employed in CRPS for diagnostic and therapeutic purposes and generally precede ketamine infusions.

Objectives: We sought to determine whether demographic and clinical factors, and technical and psychophysical characteristics of sympathetic blocks are associated with response to ketamine infusion.