Iodinated contrast dye-diluent combination exhibits longer time to full dye saturation compared to lidocaine, bupivacaine, and water in porcine cadaveric nervous tissue.

Objective: Dye-diluent combinations have different nerve-staining behavior, making locoregional cadaveric dye study findings difficult to compare. The objective of this study was to quantify the effect of 4 diluents on nerve color saturation when used in combination with commercial food dye.

Methods: 48 unpreserved brachial plexus nerves were randomized into 4 diluent groups. Lidocaine, bupivacaine, iodinated contrast, and sterile water were combined with commercial food dye (10:1), and prosected nerves were immersed in one of these groups for 1, 15, 30, or 60 minutes. Images at baseline and at each timepoint were processed using ImageJ. Color saturation was divided into quartiles (dark, medium dark, medium light, or light). The percentage of nerve area stained in each quartile was compared using a 2-way ANOVA and post hoc Tukey test.

Results: At 1 minute, water and bupivacaine had a higher percentage of area of dark saturation compared to contrast. At 15 and 30 minutes, dark and medium-dark saturation percentages of area were also larger in lidocaine, bupivacaine, and water compared to contrast. There were no differences in saturation percentages of areas between groups at 60 minutes. Within groups, all diluents had darker percentages of area saturation at 15, 30, and 60 minutes compared to minute 1.

Conclusions: In porcine nerves, the staining profiles of 2% lidocaine, 0.5% bupivacaine, and sterile water combined withcommercial food dye appear similar and may be used interchangeably after 15 minutes of exposure. When using iodinated contrast, exposures over 60 minutes yield comparable results to other diluents.

Clinical Relevance: Diluents contribute to heterogeneous nerve-staining behavior and should be considered when comparing study outcomes. If contrast is used as the diluent in cadaveric studies with postoperative imaging, researchers should be aware of the significant delay to reach a saturation level comparable to other diluent combinations.