Transdermal Application of Anesthetic Preparations Is Effective in Increasing Mechanical Nociceptive Threshold at Perineural Injection Sites in Horses.

This study investigates the impact of two topical anaesthetic creams on lowering the reaction to pain at injection sites in horses’ nerves and their subsequent effect on distal pain sensitivity. Results reveal both anaesthetics are effective in achieving surface skin numbing but do not impact pain perception farther away from application sites.

Objective and Design of Study

• The study’s objective was to ascertain the influence of two topical anaesthetic creams, EMLA and PLIAGLIS, on reducing pain sensitivity (mechanical nociceptive threshold or MNT) at two separate nerve injection sites on horses.
• It further aimed to assess any potential distal effects these preparations might have on pain perception.
• The research design was a randomised, blind and prospective study to ensure unbiased results.
• In total, 14 healthy horses were randomly assigned into two groups of 7 each, with each group treated with either EMLA or PLIAGLIS creams.

Method of Data Collection

• The study gathered data by recording the MNT at the start of the experiment (the baseline) and one hour after the application of the anaesthetic creams (T1).
• Measurements were taken at the palmar and palmar digital nerve block sites.
• Researchers also examined the skin sensation on the distal limb (away from the direct application site) by noting the MNT on the coronary band and on both bulbs of the horses’ heels.

Results and Statistical Analysis

• Analyses of the data collected employed a 3-way Analysis of Variance (ANOVA) statistical method.
• No significant difference was found between the MNT values at baseline and T1 at the control sites, proving that just the anaesthetic cream and time had a significant impact.
• A significant difference did appear between the two time points for the treated limbs, implying the creams were effective at reducing pain at the application sites.
• However, no such difference in MNT values was detected at sites distal to the treatment between the two time points, thereby suggesting the anaesthetic effect did not extend to areas farther from the application sites.

Conclusion

• Ultimately, the research concluded that both anaesthetic cream formulations are effective for superficial skin desensitization at the site of application.
• However, they appear to lack any significant impact on pain perception in areas distal to the application points.