Effect of Sedation on Diagnostic Injections

Overview

Interventional pain procedures have diagnostic, prognostic and therapeutic value. It is well-documented that the reference standard for identifying a pain generator is a low-volume block performed with local anesthetic, with or without steroid. Many factors may increase the false positive (FP) rate of diagnostic and prognostic nerve blocks; however, the use of sedation is the most controversial and remediable. Proponents of sedation argue that it has little effect on the rate of positive diagnostic blocks, and may even reduce the false-negative rate. The purpose of this study is to determine the effect of intravenous sedation on pain relief and the "false-positive rate" after diagnostic nerve blocks.

Sixty-eight patients with sacroiliac (SI) joint or sympathetically-maintained pain will be randomized in a crossover fashion to receive diagnostic nerve blocks either with or without intravenous sedation. Among those who obtain some benefit and return for a 2nd block, this 2nd procedure will be done with sedation if the first was done without sedation, and vice versa. Midazolam and fentanyl will be used for intravenous sedation, titrated to anxiolysis and analgesia. Pain scores (0-10 numerical rating scale, or NRS) and an activity log will be recorded over the 8-hours following the blocks via a pain diary. The first follow-up visit will be 4 weeks after the procedure. Patients who obtain some benefit but continue to report significant pain or who might otherwise benefit from a repeat procedure will have this second procedure performed with sedation if no sedation was given for the first procedure, and without sedation if sedation was administered for the first procedure. The post-procedure pain data will be recorded in the same fashion as the initial nerve block. The second follow-up visit will be 4 weeks after the 2nd block.