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

Pain Med. 2014 Apr;15(4):588-602. doi: 10.1111/pme.12389. Epub 2014 Feb 13.


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.

Trial registration: NCT01472835.

Keywords: Diagnostic Block; False Positive; Sacroiliac Joint; Sedation; Specificity; Sympathetic Block.

Publication types

  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Aged
  • Anesthetics, Intravenous / therapeutic use*
  • Autonomic Nerve Block / methods*
  • Complex Regional Pain Syndromes / diagnosis*
  • Conscious Sedation / methods*
  • Cross-Over Studies
  • Diagnostic Techniques and Procedures*
  • False Positive Reactions
  • Female
  • Fentanyl / therapeutic use*
  • Humans
  • Injections, Intra-Articular / methods
  • Low Back Pain / diagnosis*
  • Male
  • Midazolam / therapeutic use*
  • Middle Aged
  • Sacroiliac Joint*
  • Treatment Outcome


  • Anesthetics, Intravenous
  • Midazolam
  • Fentanyl

Associated data