Aggregation properties of triamcinolone acetonide injection in human serum: considerations when performing epidural steroid injections

BACKGROUND: Morbidity has been reported as a sequelae of crystalline steroid epidural steroid injections (ESIs), and particulate steroid size, aggregation, and embolization in brain and spinal cord may be the mechanism related to these neurologic effects. OBJECTIVE: The objective of the study was to examine the aggregation properties of triamcinolone acetonide in commonly used local anesthetics with and without human serum. SETTING: This study was conducted in an academic tertiary care center. HYPOTHESIS: Triamcinolone acetonide shows different aggregation characteristics in serum compared to a non-physiologic solution. DESIGN: Triamcinolone acetonide was mixed with lidocaine 1% (first group) and bupivacaine 0.5% (second group) in a 1:1 ratio and then mixed with either distilled water (control group) or serum ex vivo. A pathologist blinded to our hypothesis inspected all solutions under light microscopy with 100× and 400× magnifications. Total number of particulate steroid aggregates and the number of particles forming each aggregate (recorded as single,1 double,2 triple,3 quadruple,4 or large [>4} crystals) were counted. Particle size and aggregate size were measured (in μm). The ratios of quadruple to total aggregates, large to total, and quadruple with large to total aggregates were calculated. Steroid-serum solutions and steroid-sterile water were then compared. RESULTS: Triamcinolone aggregates showed an increased crystal and aggregate size when compared with other steroids. Within the triamcinolone subgroup, the mixture of lidocaine 1% and serum resulted in the largest crystal aggregates. LIMITATIONS: Whole blood analysis may have provided a more physiologically accurate model but was not chosen due to poor microscopic analysis. Serum donor variability may also have affected particle characteristics. CONCLUSION: Fewer large triamcinolone aggregates were noted in the presence of serum when compared to the non-serum control groups. However, when compared to previously studied particulate steroids, it had the largest aggregates when added to serum.