The Effect of sedation on the accuracy and treatment outcomes for diagnostic injections: A randomized, controlled, crossover study

Background and Objective: Diagnostic injections are used to diagnose myriad pain conditions, but are characterized by a high false-positive rate. One potential cause of inaccurate diagnostic blocks is the use of sedation. We sought to determine the effect of sedation on the validity of diagnostic injections. Design: Randomized, crossover study in which 73 patients were allocated to receive a diagnostic sacroiliac joint or sympathetic nerve block performed either with or without sedation using midazolam and fentanyl. Those who obtained equivocal relief, good relief lasting less than 3 months, or who were otherwise deemed good candidates for a repeat injection, received a subsequent crossover injection within 3 months (N=46). Setting and Patients: A tertiary care teaching hospital and a military treatment facility. Results: In the primary crossover analysis, blocks performed with sedation resulted in a larger mean reduction in pain diary score than those done without sedation (1.2 [2.6]; P=0.006), less procedure-related pain (difference in means 2.3 [2.5]; P<0.0001), and a higher proportion of patients who obtained>50% pain relief on their pain diaries (70% vs. 54%; P=0.039). The increased pain reduction was not accompanied by increased satisfaction (sedation mean 3.9 [1.1] vs. 3.7 [1.3]; P=0.26). Similar findings were observed for the parallel group (N=73) and omnibus (all sedation vs. no sedation blocks, N=110) analyses. No differences in outcomes were noted between the use and non-use of sedation at 1-month. Conclusions: The use of sedation during diagnostic injections may increase the rate of false-positive blocks and lead to misdiagnoses and unnecessary procedures, but has no effect on satisfaction or outcomes at 1-month.