A comparison of a transdermal eutectic lidocaine/prilocaine cream and subcutaneous lidocaine injection prior to jugular vein catheterization in horses: a randomized crossover study.

Objective: To compare horses' aversive behavioural responses to the application of 5% prilocaine/lidocaine eutectic mixture of local anaesthetics (EMLA) cream versus subcutaneous infiltration of 2% lidocaine, followed by jugular vein catheterization.

Study design: Blinded, randomized study.

Animals: A group of 26 university-owned research horses.

Methods: Each horse received both treatments at opposite jugular sites with ≥ 12 hours between procedures. One randomly assigned jugular site received 1 g cm^-2 of 5% EMLA cream 60 minutes before catheterization, while the contralateral site received 1.5 mL of 2% lidocaine subcutaneously 15 minutes prior. A 14 gauge catheter was introduced percutaneously and maintained for 20 minutes. A total of four blinded evaluators scored aversive behaviours during treatment application and catheterization using a simple descriptive scale (SDS). Treatment sites were assessed for erythema, blanching, or pain immediately after application and at 20 minutes and 24 hours post-catheter removal. Stratified multivariate Mann-Whitney U tests compared SDS values with significance at p < 0.05.

Results: Horses showed significantly lower SDS scores during EMLA application versus lidocaine injection (0.3 ± 0.3 and 0.5 ± 0.4, respectively; p = 0.012). However, during catheterization, horses treated with lidocaine had lower SDS scores than those treated with EMLA (0.4 ± 0.4 and 0.8 ± 0.5, respectively; p = 0.006), although this difference was not significant when corrected for catheter placement side (p = 0.077). Neither treatment caused adverse effects at application sites.

Conclusions and clinical relevance: The application of 5% EMLA cream was well tolerated in horses and may provide an alternative to subcutaneous infiltration of lidocaine prior to jugular vein catheterization in horses.